[HN Gopher] Displayport: A Better Video Interface
___________________________________________________________________
Displayport: A Better Video Interface
Author : zdw
Score : 447 points
Date : 2023-07-11 14:50 UTC (8 hours ago)
(HTM) web link (hackaday.com)
(TXT) w3m dump (hackaday.com)
| tshaddox wrote:
| > However, I'd like to tell you that you probably should pay more
| attention to DisplayPort - it's an interface powerful in a way
| that we haven't seen before.
|
| Lines like that really show just how long it can take for
| standards to get on the radar of mainstream tech culture. I
| remember hearing about and being excited about DisplayPort's move
| to packetized digital video in college in 2008, and seeing the
| first Macs with MiniDisplay port later that year (or perhaps it
| was in 2009)!
|
| I was actually under the impression that it has been well-known
| and commonplace for hobbyist and enthusiast PCs for well over 10
| years, but I'm probably wrong about that!
| NavinF wrote:
| > impression that it has been well-known and commonplace for
| hobbyist and enthusiast PCs for well over 10 years
|
| It is. For a long time DP was the only standard that could do
| variable refresh rate. Even today all high end monitors have DP
| while the cheapest monitors only have HDMI.
| fireflash38 wrote:
| Which is ironic considering the cost of the HDMI port is
| likely higher than the DP one due to licensing!
| hot_gril wrote:
| That, and a similar line might've been said about FireWire,
| which didn't really make it.
| dylan604 wrote:
| Maybe I agree with that, but I also know that firewire helped
| usher in the digital video era. It allowed the transition
| from tape based acquisition when media cards were
| prohibitively expensive. Audio/Video/Deck control all down
| one single cable straight from the camera to the computer was
| what really kicked the prosumer market into being able to
| lean closer to pro than consumer. Now that media cards are
| actually affordable, that does seem like ancient history. I
| could see how you might think of firewire as a failure if
| you're looking at it as a USB type transition, but for the
| camera/video professions, it served a very good purpose even
| if short lived
| pdmccormick wrote:
| I once purchased a FireWire multi-channel audio interface
| with the express intent of reverse engineering the protocol
| in order to add Linux support. I purchased a specialized
| PCI card that was intentionally non-standard (not OHCI
| 1394) but could snoop and capture traffic between a device
| and a host. I chipped away at deciphering a register map
| for awhile, but eventually better USB audio devices came
| along that had more driver support.
|
| Still trying to do the same sort of thing though with some
| audio related USB and Ethernet/IP devices so I guess I
| never really gave up the idea in my heart!
| dylan604 wrote:
| you are a glutton for punishment. a hacker after my own
| heart!
|
| i have so many unfinished things where i just knew
| something could be figured out, only to not succeed. but
| it sure is fun trying on top of learning new things as
| well.
| CameronNemo wrote:
| Do the USB devices have comparable round trip latency?
| That is where USB really hurts and where the Thunderbolt
| audio interfaces seem to fond their niche today.
|
| I'm looking forward to audio interfaces that can do USB4
| wrapped PCIe, but for now I live with the latency on
| Linux.
| Blackthorn wrote:
| RTL latency doesn't seem that bad on chips that are built
| for the purpose, like RME's. Just the off the shelf stuff
| might be less than ideal.
|
| If anything I think a problem is there's just overall too
| much slop in the whole chain, including the operating
| system, motherboard, whatever else. It's a little
| ridiculous that a $50 guitar pedal can easily get better
| RTL numbers than a $1500 computer system.
| CameronNemo wrote:
| Linux has preempt_rt pretty conveniently accessible, and
| Pipewire has some useful tuning knobs, but my Steinberg
| UR44 can't seem to keep up.
| hot_gril wrote:
| Yeah, FireWire was a necessity at the time for certain use
| cases. Even basic consumer digital camcorders required
| FW400 to pull onto a PC.
| dylan604 wrote:
| I maybe mis-remembering, but was it possible to add
| FireWire to an existing PC with an expansion card? I know
| Thunderbolt was not possible from 3rd party vendors and
| only the mobo manufacturers could offer a card. I bought
| one to make a Hackintosh, but then a mobo firmware
| disabled the card because they didn't want to support it.
| I seem to recall Firewire being the same way
| ShadowBanThis01 wrote:
| It wasn't that short-lived. All DV cameras had FireWire.
| Although Sony, per its mania for undermining industry
| standards, created a bastardized version (called I-Link,
| ugh) whose connector lacked power and required a physical
| adapter.
|
| External FireWire drives (like LaCie's) were popular for
| quite a long time, since they required no extra power
| source.
| throwawaymobule wrote:
| I think the 4 pin version was also standard, it's just
| that Sony didn't own the trademark on FireWire, Apple
| did. Sony was actually one of the companies that
| developed the spec, according to Wikipedia.
|
| I had a HP laptop with that connector, but it was
| labelled IEEE-<numbers>. Bought a 4 to 6 cable to connect
| it to an old iMac, but never bothered enough to use it.
| MBCook wrote:
| It was a standard because Sony said "we're doing this"
| and gave the FireWire group an ultimatum: standardize it
| or were not on board.
| dylan604 wrote:
| Sony also gave us a professional studio DVCam deck that
| was SDI based that allowed you to connect to of them to
| get 4x dubbing speeds. Not once did it ever get used at
| the studio I was working. Nothing else in the shop used
| that format, so it was always just realtime SDI work.
| ahh, sony
| MBCook wrote:
| Same. I live in the Mac world. When I took a job where I had to
| use PCs at work I was surprised to see they were mostly using
| HDMI with some people using older DVI equipment.
|
| I had just assumed everyone had transitioned similar to Macs
| has years before.
|
| Nope. Lots of people use/want HDMI to this day.
| tivert wrote:
| Are there any KVM switches that do Displayport _well_ (i.e. where
| switching between inputs does not look like a display disconnect
| to the PC)?
|
| I'm still using HDMI because I like to share my home multi-
| monitor setup between my personal machine and my work laptop, and
| the KVM switches are able to fool the PCs into thinking the
| monitor are always connected. Years ago I tried a Displayport
| switch, but it could not -- I assume because if the greater
| sophistication of the Displayport protocol.
| mvid wrote:
| https://store.level1techs.com/?category=Hardware
|
| This is what I use. It appears to disconnect, but also doesnt
| seem to be an issue. My machines re-organize instantly.
| zerkten wrote:
| I was looking at this as an upgrade pick and don't have any
| re-arrangement with my TESmart (TES-HDK0402A1U-USBK). What
| monitor(s) do you have?
| formerly_proven wrote:
| It's gotten better in the last year or so with Windows 10 but
| it'll still sometimes just fall apart when the display
| configuration changes, which is something that just never
| happened for any reason with HDMI/DVI.
| jamestanderson wrote:
| I got their 10gbps displayport switch to use with switching a
| single monitor between a Windows desktop PC and an M1 MacBook
| Pro. I have a 4k@144hz monitor and can get the full framerate
| and resolution with this setup. I've never had any problems,
| would highly recommend.
| c-hendricks wrote:
| Nice, I'll check these out. I went with an HDMI KVM and am
| worried about updates to HDMI making it obsolete.
| bbatha wrote:
| I had the startech one the siblings have mentioned but that
| wasn't very good and didn't do EDID emulation correctly. This
| CKL one [0] has been working really well, and supports USB 3
| which is a nice bonus so I can share my webcam. Though
| sometimes after wake up my macbook forgets about my second
| monitor (I have an M1 connected to a cable matters thunderbolt
| dock), my windows machine which has direct DP connections
| doesn't have the same issue.
|
| 0: https://www.amazon.com/gp/product/B09STVW821/
| stephenr wrote:
| The new Dell 6K has kvm (and PiP) functionality across its
| inputs, and it does appear from my modest use of this feature
| so far, that it works as you would want (ie it still thinks the
| display is connected, even when not showing that input)
| xxpor wrote:
| The magic words you're looking for are "EDID emulation". The
| KVM will continue to send the EDID data from the monitor even
| after you've switched away, which will fix that issue.
|
| It's relatively uncommon and not always implemented super well,
| but it's a requirement for any DP KVM to be not super annoying
| IMO.
|
| There was one particular KVM brand that was supposed to do it
| well whose name is escaping me now :/. I was looking at buying
| one in ~ May 2020 for obvious reasons, but they were on super-
| backorder (also for obvious reasons), so I never got around to
| it. IIRC they were about $500 for a 4 input/2 output version,
| so not cheap.
| hazebooth wrote:
| Were you thinking of Level1techs?
|
| https://store.level1techs.com/products/14-kvm-switch-
| triple-...
| xxpor wrote:
| I'm 90% sure it was, but it looks like they did a major UI
| update to the site so it's not triggering the "that was
| it!" lightbulb in my brain.
| xboxnolifes wrote:
| Alternatively, you may have been thinking about
| ConnectPro. I ordered a kvm from them around the same
| timeframe and it was delayed quite a bit from backorder.
| (Though, they also did a major UI change, so might not be
| able to tell either).
| Our_Benefactors wrote:
| Two thumbs down for connect pro. I ordered their top of
| the line 4 computer, 2 monitor DisplayPort KVM and it
| took months to arrive. I could not cycle between inputs
| using the buttons. They were more like a suggestion to
| use that signal path; I would constantly need to power
| cycle the kvm, monitors, or both.
|
| I ended up ditching it on eBay at a significant loss for
| a $30 usb switch and just switch monitor inputs manually.
| Far cheaper solution and way less fussy.
| AlotOfReading wrote:
| I use one, so I can confirm they work extremely well,
| subject to some caveats:
|
| * The _total_ cable length is important, both between the
| host / KVM and the KVM / monitor, as well as any daisy
| chained displays you have. I had to use certified cables
| to get everything working reliably with my setup.
|
| * There's a weird interaction with BIOS power on. The
| boot display drivers I have freak out if they aren't the
| active display and fail. I solve this by switching the
| KVM _before_ I turn the computer on. After everything is
| booted into an OS, it works fine to switch.
|
| * Power supply quality is important. I had some issues
| before I made sure the power supply was reliable.
|
| KVM switches are just inherently difficult little
| devices. I haven't had issues since I got it working
| though.
| drbawb wrote:
| >There's a weird interaction with BIOS power on. The boot
| display drivers I have freak out if they aren't the
| active display and fail. I solve this by switching the
| KVM before I turn the computer on. After everything is
| booted into an OS, it works fine to switch.
|
| Do you have an AMD GPU by any chance? I have the
| level1tech 2-head DP 1.4 KVM, with an AMD RX 560 on a
| Linux host, and after updating to kernel 6.4 recently my
| computer now boots fine without a monitor attached.
|
| I had a similar issue where a display had to be _on_ and
| _connected_ (i.e: active on the KVM) at boot time, or the
| GPU wouldn't work at all. I could get in via SSH, so I
| tried various amdgpu recovery options, poking the device
| to reset it, reloading the kernel modules, etc., and
| never had any luck. I just lived with the quirk. It was
| problematic because if you left home with the KVM
| selected on the Windows guest, and needed to reboot the
| Linux host remotely, you'd come home to a non-functional
| Linux desktop.
| xxpor wrote:
| I have a similar issue with a Nvidia 1080Ti on my old
| desktop. It's related to the UEFI deciding if the iGPU or
| the Nvidia GPU should be primary and to disable the iGPU
| or if the iGPU should stay enabled.
| hiatus wrote:
| Curious how you went about determining that was the
| source of the issue.
| AlotOfReading wrote:
| Nvidia on both, one consumer and one workstation. Neither
| CPU has built-in graphics iirc, nor do the motherboards
| expose the ports.
| Fnoord wrote:
| BliKVM PCIe I bought (based on PiKVM) came with an EDID
| emulator.
| seanalltogether wrote:
| Can you explain why this is beneficial? I have a mac laptop and
| pc desktop at home that i switch between depending on whatever
| I need to do. By triggering a disconnect, it means all my mac
| windows that are on the main monitor will zip back over to the
| laptop so they're still reachable if i need to access them with
| the trackpad and integrated keyboard. When I switch the kvm
| back to mac all those windows jump back to the main monitor.
| pavon wrote:
| Flaky drivers. KVM induced unresponsiveness is pretty much
| the only reason I ever have to hardboot my computers.
|
| Also, even if the drivers are solid, they take longer to
| renegotiate with a monitor that was removed and plugged back
| in compared to one they think was always there, which matters
| if you switch back and forth frequently.
|
| Lastly, sometimes the OS doesn't put things back they way
| they were when you plug a monitor back in. If you have a
| laptop which has a lower resolution display than the external
| monitor, you'll often return to find all the windows shrunk
| to fit the laptop display. Not an issue if you run everything
| full-screen, but annoying if you tile windows.
| jchw wrote:
| None of them are perfect, but I've heard good things about the
| DP switch from Level1techs. The thing is, all of them are a
| little tricky, but they mostly differ in how quirky they are,
| and I suspect the reason why people like the Level1techs DP
| switch is that they seem to at least try to alleviate some of
| the issues DP switches tend to get into.
|
| https://store.level1techs.com/products/14-kvm-switch-dual-mo...
|
| The startech one I have is alright... But Apple computers
| absolutely hate it and frequently refuse to display, and
| sometimes Windows gets stuck and USB devices stop working.
| Strangely enough... Linux doesn't ever have any problems with
| either display or input. A rare win, but fine by me.
| pxc wrote:
| The Level1Techs KVM switches are rebranded Startech switches
| with 'dumber' firmwares whose dumbness affords better
| compatibility with niche DisplayPort features.
|
| I have a bunch of them and I like them pretty well, but
| getting a bunch of computers all plugged in turns out to be a
| bit of a nightmare, especially when you need some long-ish
| cable runs or you are daisy-chaining devices (e.g., multiple
| KVM switches, adding USB hubs or Thunderbolt docks, etc.).
|
| The Level1Techs KVM switches don't meet GP's criterion for
| hotplugging behavior, unfortunately. Switching between
| devices is just an unplug and replug for them.
|
| Like you, I've found that macOS and Windows don't handle
| hotplugging monitors well, but Linux desktops (in my case,
| KDE Plasma) consistently do the right thing and don't require
| a repeater to lie to them about monitors always being plugged
| in.
|
| FWIW, I don't get the 'Apple computers just refuse to work'
| issue with any of my L1T KVMs.
| ender341341 wrote:
| > FWIW, I don't get the 'Apple computers just refuse to
| work' issue with any of my L1T KVMs.
|
| My work intel macbook worked great on it for like a year
| once I got a high quality usb-c -> displayport cable, but
| an os update borked it... though it's definitely the mac
| that's the problem as it also has problems sometimes with
| just strait to the monitor too (on the other hand 49"
| ultrawide is pushing the bandwidth near it's limits).
|
| My personal arm macbook has always worked great on it with
| even a crappy usb-c -> displayport
|
| my windows desktop also always worked great on it.
| pxc wrote:
| > on the other hand 49" ultrawide is pushing the
| bandwidth near it's limits
|
| One of the things I've learned too late is that using
| DisplayPort (and maybe HDMI, idk) anywhere near its
| bandwidth limits is not worth it for me. Having to think
| about cable run lengths as well as cable quality and
| peripheral quirks and internal Thunderbolt dock bandwidth
| allocation and so on and so on just fucking sucks.
|
| It'll probably take until the next/latest (2.1)
| generation of DisplayPort propagates before using
| multiple monitors with specs similar to my current ones
| (high refresh rate and HDR, but not even HiDPI) isn't
| painful, cumbersome, and finicky.
|
| I probably won't be able to use them by then anyway. Ugh.
| baby_souffle wrote:
| > The Level1Techs KVM switches are rebranded Startech
| switches with 'dumber' firmwares whose dumbness affords
| better compatibility with niche DisplayPort features.
|
| Rextron [1] is the actual ODM. They don't do any direct to
| consumer sales, though. That's why L1 / Startech / other
| "brands" sell them on amazon and the like.
|
| Last I spoke with the L1 guy, they were still having some
| issues with the high speed USB-C switching chips on the 1x4
| "all USB-C" model that he's got a wait-list for.
|
| [1] https://www.rextron.com/KVM-Switches.html
| pxc wrote:
| Ah! Great info. Thanks :)
| Steltek wrote:
| I had much more serious problems with a StarTech DP KVM and
| Macs. My Macbook would hang and crash-reboot. Both on the
| initial plug-in and on switching inputs.
|
| Everything else seemed to handle it fine with Linux being
| especially unphased, as usual.
| [deleted]
| shmerl wrote:
| _> Plus, It's Not HDMI_
|
| This. HDMI and its cartel that profits from its patents are super
| annoying.
| cat_plus_plus wrote:
| Maybe it is, but I also want audio, so the point is moot.
| goombacloud wrote:
| Audio is covered as well, as written in the article, I
| recommend reading it.
| TazeTSchnitzel wrote:
| The amazing thing about DVI, and by extension HDMI, is that it's
| just VGA but digital, with all the timing and synchronisation
| complexity that implies. Recall that DVI can have both an analog
| (VGA/DVI-A) and digital (DVI-D) signal in the same cable. They
| aren't independent; they share some pins and have the same
| timing. You could have made a CRT monitor that used DVI-D just by
| adding a DAC, though I'm not sure if anyone ever did.
|
| DisplayPort does away with all that legacy. I assume the hardware
| to implement it is much simpler and more reliable.
| rasz wrote:
| >DisplayPort does away with all that legacy.
|
| You wish. DP sends exactly same bytes DVI does (blanking and
| all), just broken up into packets.
| fanf2 wrote:
| The important difference is that (like VGA) DVI and HDMI
| still dedicate particular physical wires to separate red,
| green, and blue channels. Display port does not shard
| individual pixels across multiple channels: all bits (all
| colours) of a pixel are sent on the same diffpair. If a DP
| link has multiple lanes then the bits of different successive
| pixels are sent on each lane.
| rasz wrote:
| This is great, but then they drop the ball by forcing
| garbage ("interspersed stuffing symbols") between the
| packets instead of letting you use that BW.
| madars wrote:
| This also has side-channel implications, and is a reason why
| eDP is recommended in voting applications.
| https://www.eerstekamer.nl/nonav/overig/20160428/richtlijnen...
|
| >DisplayPort uses a scrambler as part of its line encoding in
| order to flatten the Fourier spectrum of its emissions and
| suppress spectral peaks caused by particular image contents.
| This reduces the chances of any particular image content
| causing a problem spectral peak during SDIP-27 and EMI spectrum
| measurements. According to the standard, the scrambler reduces
| spectral peaks by about 7 dB. As a side effect, the scrambler
| also makes it far more difficult, probably even impractical,
| for an attacker to reconstruct any information about the
| displayed image from the DisplayPort emissions. [..]
| DisplayPort uses a small number of fixed bit rates, independent
| of the video mode used. Unlike with most other digital
| interfaces, video data is transmitted in data packets with
| header and padding bytes, and not continuously with a
| television-like timing. As a result, DisplayPort cables are not
| a common source of van-Eckstyle video emanations and this again
| will make it very hard for an eavesdropper to synchronize to
| the transmitted data.
|
| Speaking of which: how does one force HDCP (say, in Linux)?
| That would transform this technology from a DRM nuisance
| (strippers easily available on AliExpress) into a Van Eck-
| countermeasure.
| angry_octet wrote:
| HDCP can't really be stripped, if it's on then something is
| an HDCP receiver. For v1.4 signals you can probably get
| something with the leaked key, but not for v2.2 as yet.
|
| HDCP itself needs to be licensed in order to generate it, and
| that licence is only available to HDMI Adopter companies.
| However there is code to get some chipsets to turn it on:
| https://github.com/intel/hdcp
|
| Grab it now before Intel deletes it completely.
|
| HDCP is really a very ugly protocol designed just for anti-
| copying, I wouldn't build anything relying on it, and
| everything is harder with HDCP from an AV integration
| perspective. If you have long links that you want to secure,
| use something like SDVoE with encryption and authentication
| (bits are easily flipped in HDCP).
| madars wrote:
| There are devices that will give you HDCP 2.3->1.4
| conversion for compatibility reasons (or maybe wink-wink
| reasons), and after that you can use a HDCP 1.4 stripper.
| There are also devices that will strip 2.2 outright (they
| are marketed as HDMI splitters but, oops, one of the two
| outputs has unencrypted signal, an honest mistake); not
| sure about 2.3 though. Completely agree that HDCP makes
| everything harder, but in this scenario it would also make
| attacker's job of descrambling the eavesdropped signal
| harder. And this is after they have overcome packetization
| and spread spectrum hurdles, which the paper suggests is
| very challenging to do, so would be a (hacky) defense-in-
| depth for DisplayPort. Even more important for HDMI/DVI
| which lacks the aforementioned hurdles.
| MisterTea wrote:
| > You could have made a CRT monitor that used DVI-D just by
| adding a DAC, though I'm not sure if anyone ever did.
|
| From memory IBM offered a crt with DVI.
| thereddaikon wrote:
| Plenty did but they were usually DVI-A or DVI-I
| pavlov wrote:
| I was guessing that the oddly beautiful 17" Apple CRT Studio
| Display [1] from 2000 might have been a CRT that used a digital
| signal cable because it had the short-lived Apple Display
| Connector, but apparently ADC carried analog too.
|
| [1]
| https://everymac.com/monitors/apple/studio_cinema/specs/appl...
| ShadowBanThis01 wrote:
| The ADC carried power, too, which is why Apple went with it.
| [deleted]
| pid-1 wrote:
| Sorry if that sounds stupid, but why isn't Ethernet used for this
| sort of high bw signaling?
| kimburgess wrote:
| Because (consumer) ethernet is low bandwidth compared to whats
| needed for video. DisplayPort 2.0 provide a 80Gbps link. HDMI
| is 48Gbps. Both already use DSC which is a mezzanine
| compression as this is already saturated for immediate needs.
|
| Ethernet is absolutely used for media transport outside of the
| consumer space. Particularly where there's a need to distribute
| signals further than what DP or HDMI can provide. The challenge
| is this always comes with a trade off. Any compression will
| result in some mix of a loss of image quality, increase to
| latency, and cost. What that mix looks like differs across
| applications.
|
| See https://sdvoe.org/, https://ipmx.io/,
| https://www.intopix.com/flinq,
| https://www.aspeedtech.com/pcav_ast1530/ for more in that
| space.
|
| https://hdbaset.org/ is the other key tech. That uses the same
| PHY as ethernet, but is a proprietary signal.
| chrisco255 wrote:
| The current Ethernet spec supports up to 1000 Gbps, but I
| think 40 Gbps is about as fast as you can find on the market
| right now. They could build multi Gbps wifi routers too, it's
| just not common in the consumer market.
| akvadrako wrote:
| Even 10Gb ethernet isn't suitable for consumers. 40Gb is
| practically only fiber which has never been successful in
| homes since it requires more careful handling.
| fsh wrote:
| The bandwidth is much too low.
| londons_explore wrote:
| If this were true, then people would be running datacenter
| networking over HDMI.
|
| Data is data - there is no benefit to designing two entirely
| different transport mechanisms for video vs other data.
|
| You could argue that video data has a deadline to meet - but
| ethernet already has lots of mechanisms for QoS and bandwidth
| reservations to make sure that someones torrents don't
| interrupt something latency sensitive. Sure, they aren't
| widely supported over the internet, but between your PC and
| your display - they can be engineered to work properly.
| FuriouslyAdrift wrote:
| HDMI has been used for stacking ports for years... I think
| it's gone out of fashion, though.
| https://www.dell.com/support/kbdoc/en-us/000120108/how-to-
| st...
| wmf wrote:
| 25 Gigabit Ethernet costs ~100x more than 32 Gigabit
| Displayport.
| aidenn0 wrote:
| Sounds like the real question is why don't people use DP
| for p2p networking links...
| xienze wrote:
| There's nothing magic about DP cables, they're just
| typically a short-ish length, which is why they can be
| high bandwidth and relatively cheap. Once you get to a
| decent length, the cables get really expensive because
| you have to put optical transceivers on either side. I
| have a 25 foot DP cable which cost over $100, for
| example.
|
| So you could do a short length, high bandwidth Ethernet
| cable, I'm sure. But the reason we don't is probably
| because differentiation between connectors is desired ---
| consumers are dumb, frankly. They'll think any old
| Ethernet cable will work. Just look at what kind of a
| mess exists with USBC.
| ianburrell wrote:
| The commonality of connector is important. Ethernet has
| stopped using twisted pair cables for higher speeds. The
| SFP transceiver means can use short DAC copper cable or
| fiber optics for longer distances. The DAC cables that
| would compete with DisplayPort are pretty cheap.
|
| Also, a big portion of the cost of networking is in the
| switch that can handle high bandwidths. My guess is that
| 25G DisplayPort switch would be just as expensive as 25G
| SFP one.
| aidenn0 wrote:
| Yeah, my original comment was based on the "100x more
| expensive" assertion. a 5m DAC cable is $40 on Amazon,
| and 25GBe cards can be had for under $200. I think it's
| probably more than $2.40 for just a 5m DP cable, so 100x
| was a gross exaggeration.
| wmf wrote:
| It's unidirectional and short reach.
| kevin_thibedeau wrote:
| HDMI is severely length limited. Ethernet has no
| millisecond level latency guarantees. Data isn't always
| just data.
| yellowapple wrote:
| > If this were true, then people would be running
| datacenter networking over HDMI.
|
| Why would they? If they need more bandwidth than what
| Ethernet provides, they'd probably just bite the bullet and
| go with fiber.
|
| ...which punts the previous question to why the industry
| hasn't gone all-in with fiber optic display connectors,
| like it has with TOSLINK for S/PDIF in the audio world.
| zokier wrote:
| Ethernet over fiber is still ethernet.
| wmf wrote:
| TOSLINK was a gimmick. In reality, optical transceivers
| are expensive and are only used when copper can't do the
| job.
| xxpor wrote:
| TOSLINK/S/PDIF is way out of date and no one uses it any
| more. Ironically, because it doesn't have enough
| bandwidth for things like Atmos.
| londons_explore wrote:
| It should be.
|
| As soon as video data is in packets, it should be routable over
| a network like any other data.
|
| Give up the custom connectors, custom cables, etc.
|
| Need a wireless display? No worries, we can route the data over
| wifi too.
|
| Need 5 displays? Thats what an ethernet switch is for. Screen
| mirroring? We have multicast.
|
| Need a KVM? Well you can probably write a few scripts to change
| which computer your screen gets it data feed from.
|
| I believe this hasn't happened simply because audio/video
| people like going to conferences to design their own standards
| every year, keep their licensing royalties, keep their closed
| club - a software-only solution over any IP network isn't going
| to fly.
| tverbeure wrote:
| They write that DP uses packets, but it's still an
| isochronous connection with guaranteed BW allocation.
|
| For video timings with high pixel clocks, the bandwidth used
| to transfer a signal is very close to what's theoretically
| available. There's no way you'd be able to do that reliably
| over something like an Ethernet cable.
|
| There's nothing sinister about how video standards are
| designed. From DP1.0 to DP1.4, which spans more than 10
| years, all changes have been incremental and most just a
| matter increasing data rates while the coding method stayed
| the same.
|
| They need a system that's very high and guaranteed bandwidth,
| high utilization, very low bit error rate, and cheap.
|
| Even today, a 10Gbps Ethernet card will set you back $90. And
| that will carry less than half the data that can be
| transported by DP 1.4 which is old school by now.
| kccqzy wrote:
| Have you tried VNC over an Ethernet cable at all? What you
| are proposing is basically having a VNC-like protocol over IP
| over Ethernet. Now try it out and see how well it works.
|
| To be even more reductive, a thought experiment is to
| consider the classic USB. Why did people even invent USB in
| the first place in the 1990s? The first USB had only 12Mbps,
| not much better than the first Ethernet at 10Mbps which had
| existed since 1980! Why didn't people who invented USB simply
| use Ethernet?
| NavinF wrote:
| Naw it's because >=40G Ethernet never saw much consumer
| adoption. QSFP DACs and optics are also kinda bulky by
| consumer standards so a lot of people would want a new
| connector. Even LC connectors would be too large for laptops.
| [deleted]
| FuriouslyAdrift wrote:
| Dante AV does this. I'm sure it's expensive, but it exists fro
| commercial applications.
| https://www.audinate.com/products/manufacturer-products/dant...
| muhammadusman wrote:
| This post was informative and I didn't realize just how different
| DisplayPort is from HDMI. Recently, I got a desktop dock that
| uses DisplayPort instead of HDMI to connect to my monitor. My
| monitor has 2 HDMI ports, 1 Type-C, and 1 DisplayPort. So far
| things have been fine but I did notice that the audio is choppy
| no matter what I do. I thought it was the dock but audio going
| from my computer > dock > my webcam's speaker works fine (all
| over usb-c). So unfortunately, it leads me to believe that the
| DisplayPort is causing this jittery audio.
| smachiz wrote:
| It might be your dock.
|
| Check to see whether it's USB or Thunderbolt. Thunderbolt docks
| are more expensive, but considerably more efficient and faster
| than USB (assuming your laptop/device supports Thunderbolt).
|
| Thunderbolt docks are basically PCIe extension devices, whereas
| USB docks attach everything as USB, with all the common
| challenges USB has on systems (like dropped audio when the CPU
| is busy).
| muhammadusman wrote:
| Thanks for the info. The dock is the CalDigit TS3 Plus dock
| and I'm using it with an LG monitor. Their page says it's a
| Thunderbolt dock so I wonder if there's anything else about
| this particular dock that could be causing this issue. Btw
| when the monitor was connected over HDMI, it was fine playing
| audio.
|
| https://www.caldigit.com/ts3-plus/
| MBCook wrote:
| That is absolutely TB and was one of the recommended docks
| in the Mac world for a long time.
|
| Have you talked to support? Or I wonder if it's an issue on
| the LG side.
| SV_BubbleTime wrote:
| No one would be able to answer this for you in your house
| with your cables with your speakers. Get another one and
| test it.
| jbverschoor wrote:
| Same here with an lg monitor on dp
| remix2000 wrote:
| With HDMI, I have both video _and_ audio traveling over a single
| cable. That is _extremely_ convenient. DP _theoretically_
| supports audio too, but AFAIK that 's not widely implemented.
| theandrewbailey wrote:
| The audio receiver industry has settled on HDMI being the only
| way to get uncompressed surround sound (5.1+) from an external
| device, like a PC. I wish they would do that over USB, too. It
| sucks having to configure an external display (even if
| duplicated) just to get good sound.
| [deleted]
| lucideer wrote:
| > _That is _extremely_ convenient._
|
| I'm open to having my mind changed but I have not really
| experienced this extreme convenience in practice. The _vast_
| majority of things I plug a HDMI cable into either don 't have
| speakers or if they do, the speakers are a bad quality
| afterthought.
|
| In actual fact, what has been an extreme inconvenience is the
| OS thinking I want HDMI audio instead of whatever much higher-
| quality* alternative output I actually want to direct my audio
| to.
|
| The _only_ time I 've ever gotten high-quality audio output
| over HDMI is via ARC, which says a lot about the need for HDMI
| audio...
|
| * When I say "much higher-quality", I don't mean HDMI is a low-
| quality audio transport, I mean the HDMI output devices more
| often than not have inferior audio output to some other
| bluetooth / 3.5mm jack device I am using.
| J_Shelby_J wrote:
| Audio over HDMI or DP has never been anything but a nuisance
| on my windows workstations. Windows finds a way to set the
| speaker monitor/mic as the system defaults at least once a
| month for me. Every GPU driver update I end up disabling the
| display's audio in device manager. Hrm... maybe I could write
| a script to do it at boot.
|
| I think it could make sense in budget friendly setups, but...
| personally I'd pay extra to not have to deal with the
| nuisance and security risk of microphone input I can't
| physically disable.
| mywittyname wrote:
| I use my PC to drive a TV for gaming and all I have to do is
| switch the sound output in Windows from Speakers to TV and
| I'm good to go. No need for splitters and multiple cables to
| get sound to both devices. The only thing I would change is
| to have Windows support outputting audio to both devices
| regardless, but keeping the settings menu open to the right
| page isn't really an inconvenience.
|
| All of my consoles work the same way: just run a single HDMI
| cable for each one.
|
| The counter point might be that my TV would have "bad audio."
| But I don't think so (at least not at the volumes I prefer),
| and even if it did, it supports audio out to connect the TV
| audio to a separate hi-fi.
| aidenn0 wrote:
| I plug my computer into my AV receiver all the time, and my
| speakers are worth more than my TV.
| bleepblop wrote:
| If your receiver doesn't support eARC, you are definitely
| not getting full resolution audio.
| aidenn0 wrote:
| I don't use ARC at all (all audio sources go through the
| receiver), so that's a non-issue for me.
| ShadowBanThis01 wrote:
| Do you not have a proper home A/V setup?
|
| Almost everything I use for media sends audio and video to my
| receiver over HDMI; the exception is analog sources, which go
| into a mixer whose output is digitized and sent over CAT-6
| cable to an optical converter sitting on the receiver.
| hot_gril wrote:
| TV connection is a pretty big use case where audio matters.
| remix2000 wrote:
| I have an audio extractor that conveniently passes the sound
| from HDMI to my desktop speakers. The extractor is connected
| between my HDMI input switcher and the [primary] monitor, so
| whichever device I'm currently using outputs the audio to the
| speakers.
| taeric wrote:
| It was very convenient for me to have my headphones plugged
| into the monitor. Made it so I could plug a single cable over
| to my laptop and have basically everything else already done.
| IggleSniggle wrote:
| Every monitor I've ever had has had terrible coil-whine
| from the headphone jack. I always try them for exactly this
| reason, and get super annoyed each time. It didn't have to
| be this way!
| deergomoo wrote:
| I have this problem on my gaming monitor, thankfully it
| also has USB-A ports so a cheap adapter has solved it.
|
| I have no idea if there are downsides to audio over USB-A
| but for my fairly basic use case ("being able to hear
| things and not hear coil whine") it works pretty well.
| lucideer wrote:
| > _headphones plugged into the monitor_
|
| That sounds cool but I've never see a monitor with a jack.
| Mine all have many USB ports, but not audio. How common are
| they?
| sublinear wrote:
| I have a 3.5mm audio jack on a cheap 4k LG monitor I've
| been using for years
| dizhn wrote:
| An audio jack is very common. Some even come with
| speakers. They are usually not very good but they get the
| job done in a pinch.
|
| I use 2 computers connected to the same monitor via hdmi
| and use barrier (and a script) to switch screens. The
| audio for the correct monitor gets activated
| automatically. It's very convenient.
| dekhn wrote:
| All the dell midrange monitors I've bought (IE, $400-$1K)
| have audio jack for headphones.
| yonatan8070 wrote:
| I have a 144Hz 1080p AOC monitor and a secondary generic
| LG one, both have an audio jack
| skipnup wrote:
| One extremely convenient situation for me is getting sorround
| sound from the TV to the AV receiver in a single cable.
| babypuncher wrote:
| HDMI was designed to accommodate home theaters. That usually
| means a sound system with good speakers. Not every user needs
| this expanded feature set, but enough do that DisplayPort
| does not make a good alternative.
|
| Here's where ARC/eARC really benefit me, and I don't see how
| this problem could be solved with DisplayPort.
|
| I have a PC and a PS5 that support Variable Refresh Rate
| (VRR) over HDMI. I bought a new TV last year that also
| supports VRR, but I did not want to replace my perfectly
| adequate 3 year old reciever that does _not_ support VRR.
| Even today, VRR support on recievers is questionable at best,
| and most users likely want their VRR devices plugged directly
| into their TV.
|
| Thanks to eARC, I can plug my PS5 or PC directly into my TV
| and have it send the PCM 7.1 surround sound audio to the
| reciever over HDMI. I can still leave other devices like an
| Apple TV or Blu-Ray player plugged into the reciever, and
| everything just works.
|
| Without eARC, I would have to fall back on TOSlink. That
| means extra cables, and dropping down to compressed dolby
| digital 5.1 if I want to keep surround sound. Using dolby
| digital on a game console incurs a pretty noticeable latency
| penalty, which is why they all default to PCM.
| inconceivable wrote:
| i have 3 computers plugged into my 4k tv (monitor) via hdmi.
| tv to dac via optical. works fine for audio+video at 4k60hz.
| sleepybrett wrote:
| I have never once used hdmi audio for anything but an a/v
| type experience. Monitor speakers are generally garbage,
| monitors generally don't support bluetooth for audio
| connectivity, their headphone jacks are often in hard to
| reach places, and I have yet to find on that supports a
| microphone. Just easier to go directly to the machine for
| audio.
| nfriedly wrote:
| I have two different LG monitors that both support audio over
| the DP cable.
| Sweepi wrote:
| I have been using DP+Audio for the last decade with a wast
| array of different monitors.
| leoc wrote:
| Unfortunately HDMI audio is also notorious for often having
| serious lag, both in absolute terms and relative to the video
| signal.
| bravo22 wrote:
| The issue is not with HDMI. The audio data is sent between
| each frame. The lag comes from the fact that TVs apply post-
| processing to video which causes it to lag relative to audio.
| ulrikrasmussen wrote:
| Isn't the whole idea of routing the audio through the display
| that it can compensate for any lag due to processing of the
| video signal? I haven't really noticed any problems with
| HDMI, and if I did, I think I would blame the display.
| michaelt wrote:
| No, the point of supporting audio and video on the same
| cable is for people plugging their DVD player into their
| TV.
| kimburgess wrote:
| That's not HDMI causing that pain. In fact, HDMI includes
| specific functionality for lip sync correction and enabling
| devices to expose both audio and video latencies they add to
| the signal.
| solarkraft wrote:
| Are you sure that it's related to HDMI? _TVs_ often do
| processing on the video signal which introduces lag, but my
| Samsung TV in "PC Mode" is virtually lag-free (and I use
| Logitech's receiver for my mouse because Bluetooth feels
| slightly too laggy for me).
| kukx wrote:
| Seems like a bug on the tv part then. They should delay
| audio accordingly to the lag.
| metaphor wrote:
| Unless the standard has been substantially relaxed since HDMI
| v1.3a, it sounds like a downstream issue.
|
| Citing SS 7.5 normative language:
|
| > _An HDMI Source shall be capable of transmitting audio and
| video data streams with no more than +-2 msec of audio delay
| relative to the video._
| AndrewOMartin wrote:
| Sounds like you need to upgrade to gold plated HDMI.
| selykg wrote:
| Better get that Monster Cable!
| tverbeure wrote:
| All modern GPUs and monitors (that's have a speaker) support
| audio-over-DP. They have for over a decade.
|
| It's widely implemented.
| naikrovek wrote:
| are you thinking of DVI or something?
|
| I've been using audio over DisplayPort for years and years and
| years without issue. every device I've ever had that supports
| DisplayPort supports audio over that connection.
| [deleted]
| haunter wrote:
| > DP _theoretically_ supports audio too, but AFAIK that's not
| widely implemented
|
| I'm using my monitor's speaker through DP since GTX 1070
| (2016). Currently RTX 4070 Ti and that works too. And it's a
| pretty mediocre AOC monitor I have.
| scarface_74 wrote:
| I have a portable external monitor that is powered and gets
| video via a single USB C port which I assume is using DP. It
| also does audio over the cable.
| adrian_b wrote:
| I have rather old NVIDIA GPUs and Dell monitors, and both the
| GPUs and the monitors support audio over DisplayPort.
|
| I doubt that there exists any reasonably recent GPU that does
| not support audio over DisplayPort, so if there are problems
| they might be caused by the monitors. I have no idea how many
| monitors have speakers and DisplayPort without supporting audio
| over DP.
| gjsman-1000 wrote:
| For some reason, outside of video, HDMI knows how to shoot
| themselves in the foot almost as well as the USB-IF.
|
| HDMI CEC? Has anyone actually got that working correctly?
|
| Anyone remember Ethernet over HDMI? Apparently that was a
| thing. (Not to be confused with HDMI over Ethernet, which
| actually has some uses.)
|
| HDMI for soundbars? We got ARC ports (Audio Return Channel).
| But it was buggy, didn't support lossless audio, needed new
| DRM, and was bad at maintaining lip sync, so introducing eARC (
| _Enhanced_ Audio Return Channel). eARC works by... scrapping
| Ethernet over HDMI and reusing the wires. Better get a new TV
| that supports it, there 's no adapters (downgrading to regular
| ARC if any part of the chain doesn't support eARC).
| aidenn0 wrote:
| CEC "just works" for me and has for as long as I've owned a
| flat panel TV (maybe 12 years or so?). Back in the day
| (before I had an HDMI receiver), I could use the TV remote to
| control the bluray player. These days I have a receiver, and
| the volume control on pretty much any device will control the
| audio on the receiver.
|
| ARC was a bit more spotty, but I moved somewhere with no live
| TV reception, so my only use-case for it went away
| (everything else routes audio through the receiver).
| ApolIllo wrote:
| HDMI-CEC is great for TVs but when I searched recently I
| found that both Nvidia and AMD do not support HDMI-CEC. This
| was disappointing to find out when I built an HTPC for my TV.
| scarface_74 wrote:
| > HDMI CEC? Has anyone actually got that working correctly
|
| I stay in lots of hotels and take my Roku stick. Most of the
| time the Roku remote can control the TV volume and power
| using CEC
| hot_gril wrote:
| "We've all gotten used to HDMI." Well that's it then, I don't
| need another less common way to do the same thing. There's always
| that theory that low-end devices will opt for DP to avoid
| royalties, but the cheapest laptops and monitors tend to be HDMI-
| only if anything because DP is more of a special feature.
|
| Similar story with H.264/5 vs VP8/9.
| gs17 wrote:
| > There's always that theory that low-end devices will opt for
| DP to avoid royalties, but the cheapest laptops and monitors
| tend to be HDMI-only if anything because DP is more of a
| special feature.
|
| Yeah, when I needed a new laptop dock, one of my annoyances was
| having to pay extra for a DP one because our lab's IT refuses
| to stock adapters or cables "because people keep using them
| instead of returning them" and they "spent extra" to get
| monitors which have a single DP port.
| bee_rider wrote:
| I just like the little retaining clips, and the satisfying little
| click you hear/feel when plugging them in.
| green-salt wrote:
| I have a love/hate relationship with them for when the release
| tab is in a hard to reach area or doesn't release well, but
| that's usually the cable's fault. Love that tactile sensation
| of it being properly mated.
| ComputerGuru wrote:
| It's a problem when the x16 slot is the bottom-most and the
| orientation is such that the clicky thing you must depress is
| on the _bottom_ side of the DP connector when plugged in, and
| your case has a ledge after the PCI slots so you cannot
| realistically depress the latch.
|
| Of course, no one would realistically encounter a
| case/GPU/cable combo like that. Right?
| jacquesm wrote:
| Hm, my sample for that situation clocks in at about 100%
| (n=1). Especially the first time I needed to unplug that
| cable I was thrown for a bit, I ended up taking the whole
| case off the floor and using a thin screwdriver to depress
| the release button from the exposed side, that did the trick.
| NavinF wrote:
| Your GPU should be in the x16 slot closest to the CPU because
| it has the most bandwidth.
|
| tbh this sounds like a self-inflicted SFF build problem
| chx wrote:
| > However, if you don't need the full bandwidth that four lanes
| can give you, a DP link can consist of only one or two main lanes
| resulting in two
|
| This is how many USB C docks operate. The USB C connector also
| has four high speed lanes and there's a mode where two are
| assigned to carry DisplayPort data and two are assigned to be TX
| and RX respectively for USB. Until DP 1.4 appeared, this meant
| you were quite limited in display resolution if you didn't have
| Thunderbolt and wanted faster than 480mbps data speed. With DP
| 1.3, two HBR3 lanes can carry 12.96 Gbit/s which is almost exacly
| the requirement for 4k @ 60Hz at 12.54 Gbit/s. DP 1.4 adds
| compression on top of this. One more beauty of DisplayPort is
| it's point to point so it's entirely possible your USB C hub will
| carry the display data from the host to the hub as compressed
| HBR3 data over two lanes and then hand it out to two monitors
| over four uncompressed HBR2 lanes to each so a modern USB C hub
| can, without Thunderbolt, drive two 4k @60Hz monitors and still
| provide multiple gigabit speed data. It's a very neat trick. This
| needs full DisplayPort 1.4 support including DSC in the host, for
| integrated GPUs in laptop CPUs this means AMD Ryzen 4000 and
| newer or Intel Tiger Lake and newer (older laptops with discrete
| GPUs might have had it, too).
|
| Handy tip: if your hub is DP 1.4 and drives multiple monitors
| then it's most likely using a Synaptics MST hub to do this
| (almost all non-Thunderbolt ones do and many Thunderbolt ones as
| well) and Synaptics provides a very very little known diagnostics
| tool called vmmdptool (available in the Windows Store). It
| doesn't replace a full DP AUX protocol analyzer of course but
| it's free and for that price it's really handy.
|
| This topic is dear to me because I have _fixed the USB C
| specification_ related to this and allow me to be damn proud of
| that: it used to erroneously say the USB data speed in this mixed
| functionality was limited to 5gbps but it is not, the limit is
| 10gbps. https://superuser.com/a/1536688/41259
|
| Ps.: When I say Thunderbolt, I am well aware of how Thunderbolt 4
| is just USB4 with optional features made mandatory. It's not
| relevant to the discussion at hand.
|
| Pps.: DisplayPort is the native video standard for USB C,
| C-DisplayPort adapters and cables are basically passive because
| they just need to tell the host how to configure the connector
| lanes. Meanwhile all USB C - HDMI cables and converters are
| active which constantly work on the DP signal to become HDMI.
| DisplayPort++ alas is not implemented with the USB C connector.
| For this reason if any compatibility issues arise it's always
| better to connect a USB C device to the DisplayPort input on a
| monitor. A HDMI alternate mode was defined in the past but it
| remained paper only and it has been declared dead this year at
| CES.
| someplaceguy wrote:
| What is the benefit of adding compression here? Does that mean
| that the bandwidth might or might not be sufficient depending
| on which pictures are being shown on the screen?
|
| If so, that doesn't seem very reliable and if not, what's the
| point of compression?
| chx wrote:
| > DSC is most often used in a Constant Bit Rate (CBR) mode,
| where the number of coded bits generated for a slice is
| always a constant that is generally equal to the bit rate
| multiplied by the number of pixels within the slice
|
| https://vesa.org/wp-content/uploads/2020/08/VESA-DSC-
| Source-...
| someplaceguy wrote:
| Ah, so basically this is typically used as lossy
| compression with a constant bit rate, which makes the
| bandwidth usage predictable/constant but depending on the
| pictures being shown (and the noise level?), it can lead to
| some visual degradation (which they say is usually
| imperceptible).
|
| That's interesting and surprising to me.
| chx wrote:
| If you consider how ~1:18 is considered visually lossless
| for x.264, a compression of 1:3 is very very likely can
| be achieved visually lossless indeed.
| jamiek88 wrote:
| Is it not compressing an already compressed image though?
| emilyst wrote:
| > Ps.: When I say Thunderbolt, I am well aware of how
| Thunderbolt 4 is just USB4 with optional features made
| mandatory. It's not relevant to the discuss at hand.
|
| Dear God, I hope this situation settles down in the near
| future. As it is I have years of USB-C-looking cables that all
| do different things but are visually indistinguishable.
| privacyking wrote:
| If you get a thunderbolt 4 cable it can do everything, at
| least until the 80gbps one comes out
| chx wrote:
| I wish the manufacturers would just adopt the USB IF
| marketing names and logos. https://i.imgur.com/H3unbD5.png
| would be a lot simpler.
|
| I also wish the USB IF defined colors for high speed lanes
| absent vs 5/10/20 gbps capable high speed lanes and then
| 60W/100W/240W power. All it needed were two color bands on
| the plastic part of the plug. If colors are too gaudy then go
| Braille-style, have a 2x2 grid on top and bottom of the plug
| where bit 0 is a little hole and bit 1 is a little bump.
| That's 16 possible data speeds and 16 possible power levels
| and so far we have only needed 4 for data and 3 for power.
|
| Intel could've added a separate row for Thunderbolt.
| bbx wrote:
| The reason why I switched to using the DisplayPort is that it's
| the one port that supports higher refresh rates ont my Dell
| monitors. I didn't realise it was more "friendly" than HDMI
| (which comes in various quality standards).
| nfriedly wrote:
| I'm annoyed nvidia for putting the current generation of HDMI on
| their recent GPUs, but leaving them with an outdated version of
| DisplayPort.
|
| For a long time, my advice to anyone was to always choose
| DisplayPort whenever it was an option. But now that has to have
| the caveat of "if you have a new high-end GPU and a fancy high
| refresh rate monitor, HDMI might actually be better for your
| situation"
| 111111IIIIIII wrote:
| And only 1 new version HDMI port but 3 old version DP ports. I
| use a dual display setup but HDR only works on mu displays with
| HDMI.
| ThatPlayer wrote:
| Yeah I hate this too because I just want to have more video
| outputs. My Valve Index doesn't like to be hotswapped plugged
| in, requiring a reboot. With 1440p144hz monitors, I just barely
| cannot run 2 of them (2x14Gbit) over a single DP1.4 (26Gbit)
| using MST. Windows will automatically drop colour down to 4:2:2
| if I try it.
|
| Not that DP2.0 MST hubs exist yet afaik, but when they do I'd
| have to get a new GPU. Which I guess is Nvidia's goal.
| gjsman-1000 wrote:
| > I'm annoyed nvidia for putting the current generation of HDMI
| on their recent GPUs, but leaving them with an outdated version
| of DisplayPort.
|
| That was due to unfortunate timing where HDMI had the
| specifications ready before DisplayPort did.
| Night_Thastus wrote:
| I thought it was because their G-Sync modules had not been
| updated to support the new DP? That was what I heard.
| Sweepi wrote:
| AMD's RX 7000 support Display port 2.0 and were released 2
| months later then Nvidia's Ada. Afaik DP 2.0 has been
| finished in 2019(!).
| bdavbdav wrote:
| I also noticed that many boards are 3xHDMI+1xDP now. My
| previous card was 3DP 1HDMI
| LoveMortuus wrote:
| I personally prefer HDMI or DVI, I don't like DisplayPort because
| on the display that I have, when I turn off the display the
| computer detects it as if I've physically disconnected the
| display, which then moves all the windows that I had open around
| and breaks my macros...
| qubitcoder wrote:
| While not specific to DisplayPort, I've been really impressed
| with the AV Access 8K KVM Switch [1]. 4K at 120Hz without
| chroma subsampling was a hard requirement.
|
| I use it with macOS Ventura and a Windows 11 desktop. It works
| nicely in conjunction with a Dell Thunderbolt 3 dock to power
| an LG OLED and support additional accessories. And it has EDID
| emulation, which is crucial for maintaining consistent display
| arrangement.
|
| I've tried other DisplayPort KVM switches with mixed success.
| This is the first one that's worked out of the box.
|
| [1] https://www.avaccess.com/products/8ksw21-kvm/
|
| [2] https://www.amazon.com/dp/B0BPRZPFM6?
| zerkten wrote:
| I /think/ this is related to the EDID support or configuration.
|
| What I do know is that you need specific EDID support when
| using a DisplayPort KVM because that switches the computer away
| on a regular basis. If you have multiple screens and a single
| screen KVM (fairly common) it will do the re-arrangement that
| you've experienced. With EDID support it keeps both output
| alive resulting in no re-arrangement.
|
| EDIT: It seems the correct term may be "EDID emulation".
| tivert wrote:
| > If you have multiple screens and a single screen KVM
| (fairly common) it will do the re-arrangement that you've
| experienced. With EDID support it keeps both output alive
| resulting in no re-arrangement.
|
| Can you tell me some KVM switches that have a working
| implementation of that feature? I'm looking for one.
|
| I'm still using a DVI KVM, because when I tried to upgrade to
| Displayport (years ago), I ran into the problem you describe
| and gave up.
| zerkten wrote:
| I have a TESmart (TES-HDK0402A1U-USBK) from https://www.ama
| zon.com/gp/product/B08259QL5J/ref=ppx_yo_dt_b... which
| works fine in this regard. This was probably the 4th
| DisplayPort KVM I tried due to keyboard issues with the
| others.
| dogline wrote:
| I'm looking too, but that one linked has HDMI out only,
| with DP and HDMI in. Don't you lose the benefit of DP
| with this setup?
| vel0city wrote:
| That's a failure of the display or your GPU, not necessarily
| the port. I've got several monitors with DisplayPort on a few
| different GPUs that don't do this behavior. Its not something
| inherent with DisplayPort.
| Aaargh20318 wrote:
| Sounds like an OS problem. When I do that it moves all open
| windows to the remaining display, but when I turn the other
| display back on it just moves them back. No special software
| installed for this, just stock macOS Ventura.
| Perz1val wrote:
| It's not an OS problem, that's how DP is supposed to work and
| that's in fact stupid
| Aaargh20318 wrote:
| It's an OS problem for not handling monitors being
| disconnected and reconnected properly.
|
| What _is_ stupid is having half your windows unreachable
| because they are on a monitor that is turned off. How does
| that help anyone?
|
| Imagine how annoying it would be on a laptop? I use my
| laptop in a meeting, and have a few windows open on its
| screen, then I arrive at my desk and plug in my 2 external
| monitors and keep my laptop lid closed. Imagine if the
| windows on the laptop display stayed there, they would be
| unreachable and would have to manually move them to my
| other screens every time I moved from a meeting to my desk.
| Same for the other way around, I disconnect from my
| monitors and take my laptop to a meeting, and then I can't
| access any of the dozens of windows I had open on my 2
| external monitors.
|
| That would be an absolutely brain dead way of working.
| theamk wrote:
| You are talking about physical monitor unplugging, while
| others are talking about monitor power off, but still
| plugged in.
|
| I agree that when monitor is physically removed, the
| windows should go back.
|
| But if it is just powered off but still plugged in? I say
| windows should stay there, just like HDMI did. For
| example I sometimes turn off monitors for less
| distractions during regular conversations.. or to save
| power before leaving.. in this case windows jumping all
| over the screen are the last thing I want.
| drbawb wrote:
| >Imagine how annoying it would be on a laptop?
|
| >That would be an absolutely brain dead way of working.
|
| For starters: the experience I want on my laptop is not
| the same as the experience I want on my desktop. I have
| two monitors at home, sometimes I like to turn off the
| wing-monitor when I am watching a movie on the center
| screen. (To avoid distraction, and also minimize glare,
| etc.) That doesn't mean I want those windows rearranged:
| that's probably going to interfere w/ the movie that is
| playing, fuck up my desktop wallpapers, icons, window
| sizes, etc. The whole point of turning off the monitor is
| to _hide those distractions._
|
| Also not all window managers suck as badly as Mac OS and
| Windows. By default I have odd-numbered virtual desktops
| go to the left montior, and even-numbered virtual
| desktops go to the right monitor. If I want to move a
| viewport to another monitor, I renumber it accordingly,
| and all the windows move to that monitor: complete w/
| their proportional positions and sizes.
|
| The idea that _a device hotplug event_ would change how
| my virtual desktops are laid out is so absurd to me that
| I switched operating systems to avoid the default Windows
| behavior. So maybe consider that paradigms and workflows
| other than "a docked laptop" exist before calling people
| braindead?
| Aaargh20318 wrote:
| > that's probably going to interfere w/ the movie that is
| playing, fuck up my desktop wallpapers, icons, window
| sizes, etc
|
| That sounds like a Windows problem.
| hot_gril wrote:
| Makes sense to move the windows if you close a laptop
| lid, but not if you turn off a monitor. You can't
| disconnect the laptop screen, but you can easily
| disconnect the monitor.
|
| I have a cheap laptop that doesn't understand a turned-
| off monitor as unusable, and it's actually way nicer that
| way.
| Aaargh20318 wrote:
| Why is it nicer? What is the use case for having
| unreachable windows?
| Joker_vD wrote:
| So that I don't see them while they still stay where they
| are! For example, preparing for a slide-show is one
| example: move PowerPoint to the second screen where it'd
| stay even if there is actually no second screen.
| Aaargh20318 wrote:
| But my windows aren't getting messed up, once I turn the
| monitor back on it restores the previous state.
|
| And the use case is simple: I have 2 monitors hooked up
| to my machine but I don't always need 2 monitors. I have
| a 34" 5k2k ultrawide and a 27" 4k in portrait mode. When
| I'm coding or using my computer for an extended amount of
| time I turn both on, but when I just want to quickly
| write an e-mail I only turn on the main monitor. I mostly
| use the ultrawide and have the portrait monitor to the
| side to dump documentation and other materials I need for
| quick reference on. Right now it's 29oC in my room and I
| don't want to turn on more equipment than needed.
| hot_gril wrote:
| This seems like a very specific situation, and you could
| disconnect the second monitor for it.
|
| Not sure about the reliability of window restoration.
| It's at least better in the latest macOS than in older
| versions.
| Aaargh20318 wrote:
| Dive under my desk and unplug the monitor from the
| Thunderbolt 4 hub or just press the power button.
| hot_gril wrote:
| Not having your windows get messed up when you turn the
| monitor on/off, which is especially relevant for TVs and
| projectors. On the flip side, what's the use case for
| connecting to a powered-off monitor and not using it? If
| I don't want to use a monitor, I won't connect it.
| hot_gril wrote:
| Is this specific to DP? I thought HDMI was the same.
| LoveMortuus wrote:
| But when I turn off my displays that are on HDMI or DVI or
| VGA, the computer still detects them like normal, like
| they're connected, because they are.
|
| I don't understand in which case the 'act like it's
| physically disconnected' behaviour would be more desired than
| what we had with all the standards before.
|
| I have read that some DisplayPort displays do have an option
| in the settings to disable this behaviour.
| Aaargh20318 wrote:
| > But when I turn off my displays that are on HDMI or DVI
| or VGA, the computer still detects them like normal, like
| they're connected, because they are.
|
| But since they're off, that doesn't make any sense, now you
| can't reach any windows on those monitors. I think the
| macOS behavior make the most sense, move them so you can
| access them, but move them back once the display is turned
| on.
| Joker_vD wrote:
| Or, you know, don't do any of those silly dances and just
| let the windows stay where they are the whole time
| between turning the displays off and on?
|
| Reminds me of that problem with video driver update on
| Windows when the screen is momentarily resized down to
| 1024x768 resolution and then instantly goes back to
| 2560x1440: all the non-maxed windows get shrunk down and
| shifted to the upper-left corner (so they would be
| visible on a 1024x768 screen) and then they just stay
| like this. It's totally useless and actually quite
| annoying.
| someplaceguy wrote:
| Sounds like a Windows problem once again...
| kiririn wrote:
| This nonsense is solved in Windows 11
| throw0101c wrote:
| > _But since they're off, that doesn't make any sense,
| now you can't reach any windows on those monitors._
|
| Perhaps I want to turn off the displays to darken the
| room.
|
| I don't want anything done with the programs/windows
| except not look at them.
| dsab wrote:
| I hate HDMI, I had many problems with this interface, in my
| prvious job my monitor was turning off when I was getting up from
| chair, same was happening in my home with differeng PC, cables
| and monitor. Such a thing never happend to me when I changed
| interface to Display Port
| BadBadJellyBean wrote:
| I just wish there was only one connector. Either HDMI or DP. I
| don't care.
| bluedino wrote:
| Oh, but there's a third. MiniDP. I have a pile of useless
| cables/adapters now, since Apple started using them but
| replaced them with USB-C back in 2015.
| cassianoleal wrote:
| There is also mini and micro HDMI.
|
| https://www.howtogeek.com/745530/hdmi-vs-mini-hdmi-vs-
| micro-...
| CyberDildonics wrote:
| Oh, but that's not a different video interface.
| mikepurvis wrote:
| I've always been surprised there aren't more receptacles out
| there that accept either a DisplayPort or HDMI plug. I've only
| seen it on one motherboard, but in retrospect, it seems obvious
| that the DisplayPort plug was designed to facilitate such a
| thing.
| yonatan8070 wrote:
| Do you happen to know what the model of the motherboard was?
| I've never heard of a receptacle that accepts both HDMI and
| DP
| mikepurvis wrote:
| Unfortunately I don't, and it's a tricky thing to Google
| for, but I believe it was something industrial where space
| was at a premium (I work in robotics).
| Kirby64 wrote:
| Are you sure you're not thinking of DP++ ?
| https://www.kensington.com/news/docking-connectivity-
| blog/di...
|
| Its a displayport connector, but the port itself can become
| an HDMI or DVI port purely with a passive adapter.
| jayd16 wrote:
| It'll be the USB-C port.
| masklinn wrote:
| For laptops it's pretty clearly USB-C with DP alt mode, just
| way too convenient to use a display as a charging hub.
|
| Desktop CG manufacturers don't care and it doesn't really
| drive sales (NVidia has completely removed it, and AMD's
| tends to be pretty buggy, it's really just DP over a USB-C
| port) so you need conversion add-in cards (usually from your
| mobo manufacturer).
|
| Also display manufacturers, standard connectivity seems to be
| 2xHDMI 1xDP and a USB-C if you're lucky (with a few cool
| oddballs providing 2xDP 1xHDMI instead). Pretty hard to do
| all-USB if that means you can't plug more than one machine to
| your display.
| immibis wrote:
| Many connectors in one. Is the video output the left port
| or the right one? How about the charging port?
| masklinn wrote:
| Just make all ports fully capable?
| Salgat wrote:
| DisplayPort and HDMI's max length is 15m, compared to USB
| 3.1's 3m.
| jsheard wrote:
| That very much depends on how much bandwidth you're pushing
| through the cable, older versions of HDMI could tolerate
| long cable runs but HDMI 2.1 is also limited to about 3m
| unless you use an expensive active optical cable.
| DisplayPort 2.0/2.1 is taking forever to come to market but
| it's going to be similarly limited in its high bandwidth
| modes when it does arrive.
| latchkey wrote:
| They aren't that expensive... 100' is $72 on Amazon.
|
| https://www.amazon.com/Highwings-48Gbps-Dynamic-
| Compatible-D...
| puzzlingcaptcha wrote:
| 40G FRL5 (4K @ 144Hz) seems to work just fine for me with
| a 8m HDMI 2.1-certified cable (copper). But I had trouble
| finding longer ones from the same vendor which makes me
| suspect it is getting close to the limit.
| BadBadJellyBean wrote:
| That's okay as well as long as it's consistent
| FinnKuhn wrote:
| and USB-C allows the transmission of displayport over USB-C
| jsheard wrote:
| It also allows the transmission of HDMI over USB-C, so you
| still have two competing standards
| Zekio wrote:
| no vendors implemented it, so whenever you are currently
| doing hdmi over usb-c it is actually hdmi over dp over
| usb-c
| johnwalkr wrote:
| Which is fine and should stay well-supported because HDMI
| is also here to stay. The trend for TVs is to include
| HDMI ports but no displayports.
| babypuncher wrote:
| The problem is these two competing standards solve
| overlapping but distinct problem sets. DisplayPort was
| designed to be used for computer monitors, while HDMI was
| designed for home theaters.
|
| This may not seem like a very meaningful distinction to
| most people, but it would become readily apparent to
| anyone trying to design a home theater around DisplayPort
| instead of HDMI. Off the top of my head, DisplayPort
| lacks any equivalents for ARC, Auto Lipsync, and CEC.
| Odds are your home theater makes use of at least two of
| these features, even if you don't realize it.
| hadrien01 wrote:
| There's also Thunderbolt over USB-C that does
| DisplayPort, but it doesn't support all the same versions
| as DisplayPort over USB-C. And there's also USB 4 but I
| don't know/understand if it changes anything.
| masklinn wrote:
| I think the most applicable bit is that USB4 adds
| tunneling modes, aside from alternate mode.
|
| I'm not entirely clear, but from my understanding
| alternate mode means the physical connection gets
| switched over, while tunneling means the tunneled data is
| sent over USB (so the communication on the wire is USB
| all along, you get nesting).
| jsmith45 wrote:
| This is essentially correct, although the encapsulation
| format is really the Thunderbolt encapsulation format,
| which is only USB in that it is now officially defined in
| the USB4 specification.
|
| USB4 hubs/docks for example, need to have the ability to
| translate from encapsulated DisplayPort to alternate mode
| for its downstream ports. USB4 hosts need to support both
| encapsulated and alternate modes in the downstream ports.
| The idea is that if a display device does not want to
| implement any other non USB 2.0 peripherals (2.0 has
| dedicated lines so it can support those), it can
| implement only alternate mode, (and not need to support
| the complexities of encapsulating USB4), plus all USB4
| hosts needing to support DisplayPort means you know you
| can connect such a screen to any USB4 device and have it
| work (although supporting multiple screens like this is
| optional).
|
| One thing to not though is that DisplayPort alternate
| mode has the option of reversing the device->host wires
| of USB-C lanes and thus get 4 lanes of host->device data,
| for 80Gbps at Gen 3 speeds if using both lanes.
|
| USB4 V1.0 does not support lane reversal, and USB4 V2.0
| can reverse only one bidirectional lane, since it still
| needs to support device->host data. I think this lane
| reversal is only possible when using the new new Gen 4
| speeds, which provided 80Gbps symmetric, or 120/40 Gbps
| asymmetric.
| vel0city wrote:
| It allows it, but can you actually buy any products for
| it?
|
| https://www.notebookcheck.net/The-demise-of-HDMI-over-
| USB-C-...
|
| > True USB-C to HDMI adapters are no longer going to be a
| thing. The HDMI Alt Mode is more or less history, and
| DisplayPort has won. Notebookcheck spoke to HDMI LA and
| the USB-IF about it.
|
| > HDMI LA said that it doesn't know of a single adapter
| that has ever been produced. Similarly, at the USB
| Implementers Forum (USB-IF), people who are familiar with
| the certification process have yet to see a true USB-C to
| HDMI adapter.
| bandrami wrote:
| There's an oscilloscope screen that does the conversion
| in software and was the bane of my existence last year.
| ianburrell wrote:
| There is also MHL alt mode. The HDMI alt mode was
| horrible because it used the whole USB-C cable as HDMI
| cable preventing any other users. MHL is HDMI but over a
| single pair.
|
| My understanding is that all the USB-C to HDMI adapters
| are using DisplayPort because that is more widely
| supported by devices. And the conversion chips are just
| as cheap as MHL to HDMI.
| [deleted]
| jdiff wrote:
| The article mentions the death of HDMI altmode. Is it
| actually widely supported?
| jsheard wrote:
| It seems not, I missed that HDMI altmode is still stuck
| at HDMI 1.4 and they're not making any attempt to bring
| it up to HDMI 2.0. DisplayPort indeed won in that case.
| EVa5I7bHFq9mnYK wrote:
| I recently switched DisplayPort connecting my laptop to the
| monitor for USB-C, didn't see any difference, except now I
| get video (4kx60hz, max for my monitor), audio, can connect
| mouse and keyboard directly to the monitor, and the cable is
| thinner and lighter. Am I missing on something?
| deergomoo wrote:
| Don't forget power delivery! Having a truly one-cable
| docking setup is a godsend if you need to switch between
| devices regularly.
| jsight wrote:
| I just wish the Google Pixel line supported display out over
| USB-C.
| gaudat wrote:
| I really really hope that my LG has a DisplayPort input. They do
| offer a monitor that is the same size and I believe the same
| panel, but the price increase does not really justify it. So sad
| that I have to bear with the hell of DP/USBc to HDMI
| converters...
| binkHN wrote:
| I didn't realize Multi-Stream Transport (MST) requires OS
| support, and I was surprised to find out MacOS, with its great
| Thunderbolt support, does not support this. "Even" ChromeOS can
| do MST.
| stephenr wrote:
| Technically macOS _does_ support MST. But it _only_ supports it
| to stitch together for a single display. It does _not_ support
| daisy chaining two displays.
|
| Thankfully, every Mac for the last 7 years has Thunderbolt3 at
| least, so getting dual-4K-display from a single port/cable is
| still very doable, you just need a TB3 to dual DisplayPort or
| HDMI adapter.
| deergomoo wrote:
| You can daisy chain the Studio Display and Pro Display, and
| you could daisy chain the old Thunderbolt Display. Is that
| using some custom thing over Thunderbolt rather than MST?
| bpye wrote:
| Well except for some of the Apple Silicon machines. The M1
| (and maybe M2?) only have two video output blocks, of which
| one is already used for the internal display. It's honestly
| the biggest complaint I have about my M1 MBP. Yes DisplayLink
| or whatever it's called exists but the performance is bad.
| stephenr wrote:
| Ugh, right. Probably a freudian slip that I just mentally
| pretend those configs didn't come after half a decade of
| ubiquitous multi-display support on Macs.
| stephenr wrote:
| But - and I can't believe I forgot this in my other reply -
| this is one thing that really grinds my gears about Apple's
| releases since 2018, on everything except the Mac Pro (both
| 2019 and 2023).
|
| They hard-code one DisplayPort stream to *something* other
| than Thunderbolt.
|
| On laptops, they hard-code one via eDP to the display,
| which is useless if it's in clamshell mode.
|
| On Mac Mini, Mac Studio, and the MacBook Pro with HDMI
| port, one stream from the GPU is hard-coded to the HDMI
| port. If you want maximum displays, always has to be from
| HDMI.
|
| But neither the 2019 or 2023 Mac Pro have this limitation.
| Even on the 2019 model where the HDMI ports were physically
| on the card - they could route all video streams via system
| TB3 ports.
|
| I just checked and the base M2 Mini, and the M2 Pro MBP
| seem to finally allow using two video streams over the TB4
| ports, - but the M2 Ultra Studio, with the exact same SoC
| as the M2 Ultra Mac Pro, still has this stupid artificial
| limit.
| jon-wood wrote:
| I assume you got one of the original M1 MBPs. The more
| recent models have more display blocks. M1 Pro can drive
| two external displays, and I think the M1 Max can do three
| or four. I'm still slightly pissed Apple ever shipped the
| original M1 MBPs, they were horrible machines.
| spockz wrote:
| Although I wished i would have gotten the 15" and a
| bigger hard drive, I'm still very happy with my first gen
| 13" mbp. Also the fact that I can just plug in usb
| c/Thunderbolt monitors and the screen just instantly
| displays and windows reconfigure without flickering is
| amazing.
| bpye wrote:
| It is really my only complaint about it, and since I
| needed a new laptop at the time it still made sense. I
| would definitely rather one of the 14" ones now - but not
| enough to buy a new device.
| bdavbdav wrote:
| Yep. Super annoying. I have a Dell WD22TB4 which works great to
| drive 3 monitors for everything, except my Mac.
| rbanffy wrote:
| I was _very_ disappointed that HDMI transfers a constant bit-rate
| stream of pixels - VGA, but digital. I expected that, given most
| display devices can at least hold a full frame in-memory, that
| the stream could be limited to the parts of the image that
| changes, allowing higher frame rates when less than the full
| frame changes.
|
| That, and generating a signal could be much simpler than bit-
| banging on a DAC.
| hooverd wrote:
| For a brief moment, being able to daisy-chain displays was so
| cool. Now it feels like we've regressed to wrangling HDMI cables
| out of a USB-C hub.
| qwertox wrote:
| This is a really well written article. If you haven't bothered
| reading about DisplayPort because you knew VGA, somewhat knew DVI
| and thought that HDMI is the culmination of it all, where then
| DisplayPort is just some further kind of evolution, this article
| does a really good job at explaining how DP is very different and
| something new, something worth knowing about.
|
| The core sentence which made me actually read the article was
| "DisplayPort sends its data in packets." and does a good job at
| explaining what this means and how this differs from HDMI.
| ben0x539 wrote:
| As a habitual comments skimmer, thanks for selling me on the
| article. :)
| Ajedi32 wrote:
| > A carefully shaped money-backed lever over the market is
| absolutely part of reason you never see DisplayPort inputs on
| consumer TVs, where HDMI group reigns supreme, even if the TV
| might use DisplayPort internally for the display panel
| connection.
|
| Curious about this. Is the HDMI standards group engaging in anti-
| competitive behavior to prevent DisplayPort from taking over on
| TVs? I've always assumed it was just momentum.
| msie wrote:
| I was just thinking about USB-C vs Lightning... What if the EU
| were to mandate HDMI over DisplayPort?
| Dr4kn wrote:
| The EU Generally chooses the more open and cheaper
| alternative. They did this with phone charging, car charging
| and would probably do the same with display connectors.
|
| USB C is the cheaper and more capable connector
| sedatk wrote:
| > Is the HDMI standards group engaging in anti-competitive
| behavior
|
| They don't need to, the whole industry is behind it:
|
| > The HDMI founders were Hitachi, Panasonic, Philips, Silicon
| Image, Sony, Thomson, and Toshiba.
|
| > HDMI has the support of motion picture producers Fox,
| Universal, Warner Bros. and Disney, along with system operators
| DirecTV, EchoStar (Dish Network) and CableLabs.
| 6D794163636F756 wrote:
| [dead]
| sylware wrote:
| Don't forget, displayport is worldwide royalty free, not hdmi
| (similar issue than mpeg/av1, arm|x86/risc-v, etc).
| amelius wrote:
| Can we please get monitors that can find their signal within
| 100ms?
|
| Can we please get monitors that communicate their orientation
| (portrait/landscape etc.) to the computer?
| jwells89 wrote:
| The Apple Studio Display autodetects rotation and lets the
| connected computer know so it can adjust the picture
| accordingly, but it connects over Thunderbolt. It should be
| possible for monitors to do this over USB-C too, but I'm not
| sure about plain DisplayPort or HDMI.
| theodric wrote:
| _sigh_
|
| Ok FINE I will move the goalpost
|
| I want all that in a monitor that doesn't cost more than a
| typical modal monthly income in Europe
| deergomoo wrote:
| > it connects over Thunderbolt
|
| Not exclusively--it supports regular DP Alt Mode, though no
| idea if those advanced features also work.
| deergomoo wrote:
| > Can we please get monitors that can find their signal within
| 100ms?
|
| TVs too--with various HDR standards, VRR etc becoming more
| popular these days I quite often find myself staring at a blank
| screen for 5-10s
| amelius wrote:
| With Smart TVs being the only option these days, I'm thinking
| about building my own TV from a computer monitor.
| wcfields wrote:
| If we lived in a just, and virtuous world we'd all be using cheap
| coaxial cables with BNC connectors via whatever version of SDI is
| the highest bit rate.
| mschuster91 wrote:
| SDI can't do _any_ communication between the source and sink.
| You can do a limited form if you use two SDI cables (one
| upstream, one downstream) which is what stuff like BlackMagic
| 's bi-directional micro converter does, but IIRC that's only
| used for talkback to the camera operator and HDMI CEC messages
| which is how they implement things like their ATEM Mini
| consoles triggering recording - not for DDC-style format and
| framerate negotiations.
|
| Also, device manufacturers don't do SDI on consumer devices
| because SDI is by definition unencrypted and uncompressed, so
| it's at odds with HDCP.
|
| [1] https://www.blackmagicdesign.com/products/microconverters
| ShadowBanThis01 wrote:
| BMD has done some innovative things through their SDI port,
| specifically enabling camera control with an Arduino-add-on
| board.
|
| Someone finally did what I've wanted to see for years: built
| a follow-focus unit that controls the focusing motors in the
| lenses, so you don't have to bolt a ridiculous contraption
| (and janky focusing-ring adapters) onto a lens to turn its
| (non-mechanical) focusing ring manually.
| mschuster91 wrote:
| What I want to see is someone dump the FPGA in these Micro
| Converters and hack it to add an USB interface. The Micro
| Converters are _all_ just the same in the interior: SerDes
| units and clock /redrivers on the I/O ports and an FPGA
| that additionally has an USB connection which is used to
| power the converter but _could_ also be used to do other
| things.
|
| That FPGA should be powerful enough to do a lot of
| interesting things - anything from fooling around with
| commands (like with the Arduino board) to image
| manipulation (e.g. a watermark embed).
| NavinF wrote:
| That would suck. I'd need at least 4 coax cables for each
| monitor.
|
| Btw DP cables are often twinax and eDP cables are often
| microcoax.
|
| In a just, and virtuous world we'd all be using cheap SMF
| cables with LC connectors
| formerly_proven wrote:
| 12G-SDI of 2015 is the first SDI revision to surpass DVI from
| the 90s in terms of bandwidth. 24G-SDI, which seems to only
| exist on paper so far, has about one quarter the bandwidth of a
| DisplayPort 2.0 link.
|
| It's unsurprisingly annoying trying to compete with a bundle of
| cables using only one wire.
| spearman wrote:
| > A carefully shaped money-backed lever over the market is
| absolutely part of reason you never see DisplayPort inputs on
| consumer TVs, where HDMI group reigns supreme
|
| What does this actually mean?
| green-salt wrote:
| HDMI is licensed, Displayport doesn't need one. I'm sure
| there's money changing hands in the TV sector of most display
| manufacturers.
| Veliladon wrote:
| HDMI predates DP by 5 years, switching wouldn't enable any
| specific use case, and that 5 years head start means HDMI has
| market inertia.
|
| Yes we should use it because it's better but the practicality?
| There's so much gear that's HDMI that would have to be replaced
| or require new active adaptors. It's so much industry and
| consumer effort for such a marginal gain.
| lucideer wrote:
| Forget all the other pros/cons - MST makes it worth any
| industry & consumer effort alone.
| hot_gril wrote:
| How many people use multiple external displays? For the power
| users who do, there are already good enough solutions.
| lucideer wrote:
| I don't have data on this but if my anecdata is anything to
| go by, power users aren't your typical multi-monitor
| users...
| patrickthebold wrote:
| My monitor is fairly old, but it only does 30Hz on the hdmi
| cable and 60Hz on the display port cable. I'm not sure the
| exact versions. I think its displayport 1.2 and HDMI < 2. So
| for me, it was super important to get display port out.
| babypuncher wrote:
| HDMI also supports a lot of home theater specific features that
| DisplayPort does not.
|
| DisplayPort never could have replaced HDMI because DisplayPort
| never tried to solve the same problems HDMI did.
| metaphor wrote:
| > _HDMI predates DP by 5 years..._
|
| - HDMI v1.0 initial release = 2002-12-09
|
| - DisplayPort v1.0 initial release = 2006-05-01
|
| To be sure, just under 3.5 years; HDMI rolled into v1.3 a month
| after DisplayPort v1.0 saw the light of day. Agreed on the
| impact of market inertia.
| Dalewyn wrote:
| HDMI's marketshare has nothing to do with its headstart: HDMI
| is backed by the entire entertainment industry and was
| designed for televisions, while DisplayPort is backed by VESA
| and other computer hardware manufacturers and was designed
| for computer monitors.
|
| For every computer monitor there are hundreds if not probably
| thousands of televisions.
|
| HDMI's marketshare has everything to do with who the players
| involved are and just how much weight they have to throw
| around. Even computer hardware generally have more HDMI ports
| than DisplayPort ports.
| Sparkyte wrote:
| my argument display-port of usb-c is a better interface for
| flexibility and utility
| mschuster91 wrote:
| > in fact, the first time we mentioned eDP over on Hackaday, was
| when someone reused high-res iPad displays by making a
| passthrough breakout board with a desktop eDP socket. Yes, with
| DisplayPort, it's this easy to reuse laptop and tablet displays -
| no converter chips, no bulky adapters, at most you will need a
| backlight driver.
|
| I'm a bit confused by the linked project's PCB [1] - if all
| that's needed is a backlight driver, why all the differential
| pairs between the microcontroller and the eDP FFC?
|
| [1]
| https://hackaday.io/project/369/gallery#9e4a0fef705befb8030b...
| bpye wrote:
| The schematics are available [0]. It looks to me like the MCU
| is doing some sideband control, but the DisplayPort signal
| itself is passed through unmodified.
|
| [0] https://github.com/OSCARAdapter/OSCAR
| crazygringo wrote:
| > _Just like most digital interfaces nowadays, DisplayPort sends
| its data in packets. This might sound like a reasonable
| expectation, but none of the other popular video-carrying
| interfaces use packets in a traditional sense - VGA, DVI, HDMI
| and laptop panel LVDS all work with a a stream of pixels at a
| certain clock rate._
|
| Funny, a stream of data at a constant rate makes much more sense
| to me intuitively than packets, specifically for uncompressed
| video.
|
| Are there any downsides to packetization, like increased latency
| or dropped frames or anything? Or not really, is it all upsides
| in being able to trivially combine multiple data streams or
| integrate easily into hubs?
| wtallis wrote:
| > Funny, a stream of data at a constant rate makes much more
| sense to me intuitively than packets, specifically for
| uncompressed video.
|
| Sure, until you start trying to design the transceivers and
| realize that supporting two or three fixed standard data rates
| is a lot simpler than supporting a continuously-variable clock
| speed. Every other high-speed digital interface operates at
| just a few discrete speeds: SATA/SAS, PCIe, Ethernet, USB.
|
| The fact that DVI and HDMI were such a shallow digitization of
| VGA's racing-the-beam meant features like variable refresh rate
| (Gsync/Freesync) showed up far later than they should have. If
| we hadn't wasted a decade using CRT timings (and slight
| modifications thereof) to drive LCDs over digital links, it
| would have been more obvious that the link between GPU and
| display should be negotiated to the _fastest_ data rate
| supported by both endpoints rather than the lowest data rate
| sufficient to deliver the pixels.
| ansible wrote:
| > _... If we hadn 't wasted a decade using CRT timings (and
| slight modifications thereof) to drive LCDs over digital
| links ..._
|
| Don't forget the decade or so (late 1990's to early 2000's)
| where we were driving LCDs over _analog_ links (VGA
| connectors).
|
| I had purchased a pair of Silicon Graphics 1600SW monitors
| back in the day, which required a custom Number Nine graphics
| card with an OpenLDI display interface. It was many years
| since those were introduced to the market that DVI finally
| started becoming commonplace on PC graphics cards.
|
| Using the mass-market LCD monitors in the late 1990's was a
| frustrating affair, where you had to manually adjust the
| timing synchronization of the analog signal.
| samtho wrote:
| > Funny, a stream of data at a constant rate makes much more
| sense to me intuitively than packets, specifically for
| uncompressed video.
|
| There is a data rate floor for how fast the device that outputs
| must meet. We've surpassed this (due to optimization at the
| silicon level, designing hardware who's sole job it is to send
| bursts of data) and we end up running out of data in the buffer
| periodically because it's just so fast. Because analog is real
| time, you can squeeze much else in that data stream but with
| digital, we are afforded the luxury of packet switching instead
| of that line being idle, we can pump even more down the linen.
|
| > Are there any downsides to packetization, like increased
| latency or dropped frames or anything? Or not really, is it all
| upsides in being able to trivially combine multiple data
| streams or integrate easily into hubs?
|
| If I recall correctly, the timing and data rates is all
| prearranged based on reported capacity and abilities of the
| receiving device and it won't even attempt to support multiple
| streams if it is incapable of doing so or the data channel
| established cannot fully support the bandwidth required.
| tverbeure wrote:
| Latency is limited to the amount of buffering that's present in
| the interface logic (on sides). In the case of regular DP,
| there's just a few FIFOs and pipeline stages, so the latency is
| measured in nanoseconds.
|
| When using display stream compression (DSC), there's a buffer
| of 1 line, and a few FIFOs to handle rate control. At the
| resolution for which DSC is used (say, 4K/144Hz), the time to
| transmit a single line is around 3us. So that's the maximum
| additional latency you can expect.
| askura wrote:
| The only downside with DP is just devices that actually have that
| versus HDMI / Mini hdmi.
|
| This post though has made me annoyed as DP is clearly the better
| standard.
| nfriedly wrote:
| Agree with you there. I'd be much happier if my Raspberry Pis,
| cheap USB-C hubs, cheap monitors, etc. all had DP instead of
| HDMI.
|
| It's extra annoying when you realize that you're paying more
| for royalties and sometimes additional hardware (e.g. in a
| USB-C hub that uses DP internally but converts to HDMI for the
| output) just to get an inferior interface.
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