[HN Gopher] Sending audio to LKV373 HDMI extenders
___________________________________________________________________
Sending audio to LKV373 HDMI extenders
Author : luu
Score : 57 points
Date : 2023-07-03 00:19 UTC (22 hours ago)
(HTM) web link (eta.st)
(TXT) w3m dump (eta.st)
| squarefoot wrote:
| There was some effort to reverse engineer those devices [1] so
| that one could use for example either transmitters or receivers
| paired with normal PCs and not just connecting them straight each
| other. There are also newer models around, though I'm not aware
| of any reverse engineering efforts so far.
|
| If you want to tinker with them, please leave some writeup of the
| results. Beware that there are both HDMI over IP and
| aesthetically very similar, but often cheaper, HDMI over Ethernet
| cable adapters. The 2nd ones contain no brain and can't do any IP
| encapsulation, they're essentially just level translators using
| CATx cable to carry the HDMI signals, and of course aren't
| compatible with any network devices, switches, etc. For that use,
| you want HDMI to IP transmitters and receivers, which should be
| clearly marked as capable of working in a network environment.
| Check carefully the features before buying, because some among
| the stupid level translators sold on the usual channels are
| marked as HDMI over IP, which they clearly are not.
|
| 1 - https://blog.danman.eu/reverse-engineering-lenkeng-hdmi-
| over...
| rektide wrote:
| People are amazing. I love this. Adore it. A thread of various
| awesome enterprising hackers, searching for truth, and using
| observability & tools to uncover meaning. Then bend reality to
| their whims & desires. This is the best human spirit. It's a pity
| technology so often obstructs rather than builds this human
| mastery. Alas! Never-the-less, humanity persisted. Against the
| throws of corporate-controlled limiting tech. Break out that
| wireshark & conquer in the name of freedom! Become great! Be
| unbounded.
|
| I have huge respect for the Chromecast ecosystem, but there's so
| many weird prickly points for it. For a while I had a chromecast
| plugged in to a computer which then variously resent the output.
| This looks like a great way to do the same but simpler/dumber.
| One of the specific flaws of Chromecast is that if you stream a
| video, it can only go to a single device. Meaning my whole home
| audio does no good. Something like this could help me work-around
| that limitation. It's great how absurdly flexible these devices
| are, but it sucks enormous egg that Chromecast apps will only
| stream in the first place to signed Chromecast devices; this
| whole thing should be a non-issue I can software workaround. But
| a hardware workaround like this is adequate.
| awehoiwaegw wrote:
| [dead]
| jaywalk wrote:
| I didn't even know HDMI extenders over IP existed! I wouldn't use
| it for TV/movies, because the re-compressed picture can't look
| all that great. But I could imagine plenty of uses for something
| like that!
| bobsmooth wrote:
| You can do HDMI over a lot of things. They all work by encoding
| the video stream, usually h264, and sending it over the
| network. Check out HDBaseT which does video, ethernet, USB and
| power over a single cat5e cable.
| dylan604 wrote:
| Why do you assume the signal is being recompressed or in any
| other way manipulating the image?
| belthesar wrote:
| You can look at the protocol analysis in the post to see that
| it's sending MJPEG
| monocasa wrote:
| Because a 1080p60 video stream is about 3Gb/sec on the wire
| uncompressed like happens over HDMI. 1920w * 1080h *
| 3colorbytes * 8bits/byte * 60fps = 2,985,984,000 bits/sec.
| dylan604 wrote:
| Okay, but the original signal is not RAW uncompressed
| either. It's just a serial signal, so converting that into
| IP packets is pretty much all I'm assuming this is doing
| and then converting those back to an HDMI formatted signal
| on the other end. The only thing different about this unit
| from others is that it's actually turning them into actual
| network traffic to connect to an existing network.
| monocasa wrote:
| > Okay, but the original signal is not RAW uncompressed
| either.
|
| HDMI is in fact the RAW color values, uncompressed. Each
| of the color channels are serial, but that doesn't really
| change anything about the raw bitrate.
| jacquesm wrote:
| I suspect that just delta compression would reduce the
| required number of bits considerably.
| duskwuff wrote:
| Lossless compression isn't a good fit for real-time
| video. Being able to get some compression ratio on a
| "typical" image means your stream will drop out when the
| user has an image on screen which doesn't compress well.
| Clamchop wrote:
| Just to throw a little more hair-splitting, we're not
| talking about raw data, either, raw being a term of art
| for unprocessed or minimally processed data read from a
| device (like an image sensor). It usually can't be
| displayed without some interpreting.
|
| HDMI video signal is uncompressed but not raw.
| metaphor wrote:
| Much closer to 5 Gbps when you factor in
| horizontal/vertical blanking + TMDS 8b10b encoding.
| monocasa wrote:
| For sure, I'd simply expect even a simple non-compresing
| bridge to strip a lot of the 'dead air' and expansion at
| the physical layer. Just wanted to show that even best
| case of simply the color value bits leaves you with ten
| pounds of potatoes to fit into a five pound bag.
| mnd999 wrote:
| That's very doable on a 10gb Ethernet network which is
| becoming more and more normal.
| monocasa wrote:
| It's going to be a while before 10Gb ethernet is
| available on devices that cost ~$30/pair.
| toast0 wrote:
| You're right, but used dual port 10g ethernet cards do go
| for about $30/each... Of course, that doesn't get you
| hdmi encode/decode, and not new.
| metaphor wrote:
| Irrelevant. The hardware under scrutiny is a chinesium
| HDMI over IP extender with 1 Gbps Ethernet PHY at best.
| duskwuff wrote:
| Well, for one, the fact that it's streaming frames as motion
| JPEG...
| dylan604 wrote:
| Where do you see that? I quickly glanced at the Amazon
| listing, and saw nothing about this. I could have glanced
| too quickly and missed it, but it just seems like a totally
| strange thing for it to do.
| mrpippy wrote:
| It's in the article
___________________________________________________________________
(page generated 2023-07-03 23:01 UTC)