[HN Gopher] Video encoding requires using your eyes
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Video encoding requires using your eyes
Author : zdw
Score : 40 points
Date : 2025-02-28 04:33 UTC (1 days ago)
(HTM) web link (redvice.org)
(TXT) w3m dump (redvice.org)
| okramcivokram wrote:
| I don't see (or maybe don't recognize) any issues with the image
| that they're talking about (ringing, color shift, or fake
| details). It most certainly doesn't look awful to me, it looks
| exactly the same, only a bit sharper.
| sgarland wrote:
| It's mostly only visible in the closeup of the kid. There are
| hairs that have been unnecessarily accentuated, and his eye and
| eyebrow outline look hyper-sharpened, with rough edges.
|
| The non-zoomed image looks fine to me, and I (to some extent)
| know what I'm looking for. Some private torrent trackers that
| pride themselves on having transparent encodes will look for
| this kind of stuff; you have to do multiple test encodes
| tweaking various parameters to ffmpeg, agonizing over A/B
| screencaps, only to inevitably be told you either missed some
| minuscule detail in a single scene, or that your encode is
| bloated.
| AlotOfReading wrote:
| You can see some ringing in the sky around the trees and on the
| line between the crow's beak/feathers if you look closely.
| (Alvin's?) fur goes much farther down his forehead as well.
| People who work deeply with codecs are usually hypersensitive
| to these sorts of issues that mere mortals like us need to try
| to see.
|
| There used to be a legendary blog called "Diaries of an x264
| developer" by Fiona Glaser [0] where she'd go on long rants
| about various ways to cheat in encoder comparisons [1], much
| like this.
|
| [0]
| https://web.archive.org/web/2012/http://x264dev.multimedia.c...
|
| [1]
| https://web.archive.org/web/20130215095527/http://x264dev.mu...
| machrider wrote:
| Appreciate this, I was feeling the same way as the original
| comment. It looks maybe over-sharpened, but I don't see
| anything as glaring as the text of the article makes it
| sound! (Of course, I'm not a video codec developer.)
|
| It does remind me of how stereo & speaker manufacturers
| sometimes boost treble a little bit (rather than being
| perfectly "transparent" to the original signal) because it
| gives the impression of clarity. But ideally each step in the
| processing chain "colors" the signal as little as possible,
| because those little differences can add up.
| LegionMammal978 wrote:
| Yeah, audio response curves have always been a bit
| confusing to me. Like, they say that headphones should use
| a Harman curve because that sounds 'best' to listeners, but
| how valid is it as an objective measure? (E.g., will
| listeners 50 years from now find a different curve
| 'better', the same way that instrument tuning has changed
| over centuries?) And how much of it is responding to
| current practices in recording and mixing?
|
| Of course, you won't get a sound as if you're in the same
| room (without a very fancy setup), so you'll generally want
| some sort of transformation to get an acceptable output.
| And artists often want to aim for a certain effect on top
| of that. But with how things currently are, many of the
| decisions going into the final sound are very opaque.
| crazygringo wrote:
| I agree the "negative" artifacts are almost impossible to
| see, and came here to the comments to see what the heck the
| author was talking about.
|
| > _People who work deeply with codecs are usually
| hypersensitive to these sorts of issues that mere mortals
| like us need to try to see._
|
| I think that kind of shows that the author is unfairly
| critical.
|
| They're saying "this should not have shipped", when it seems
| _just fine_ to us "mere mortals".
|
| Yes, video encoding requires using your eyes. But it also
| seems like it should use normal eyes, not hypersensitive
| eyes...?
| dist-epoch wrote:
| Ringing is pretty obvious to me. It has a specific meaning in
| this context, it means edges are over-sharpened to the point
| that "fake" extra edges appear.
|
| https://en.wikipedia.org/wiki/Ringing_artifacts
| SG- wrote:
| the fact that it looks different is the problem.
| mrob wrote:
| The ringing is most obvious in the striped shirt in the
| painting on the wall. It's added entire new stripes that don't
| exist in the original.
| mikeryan wrote:
| Sorta related story.
|
| I worked for a cable channel (TechTV) in the late 90s early 2ks
| (until Comcast bought it, laid everyone off and turned it into
| G4) this was the early days of cable VOD. At that time you had to
| pay a service by the minute to watch your video before they'd
| distribute it. That was the QA forced on you by the cable
| companies.
|
| The fun note is that those services charged double for "adult"
| content.
| xmprt wrote:
| Is it just me or does the author here sound like they're hating
| just to hate? The writing doesn't sound that terrible. Maybe it's
| a bit amateur but isn't that what you're expect from an
| engineering blog post written by people whose day job is to write
| code. And for a layman, the image comparison isn't as bad as they
| make it out to seem.
| kelseyfrog wrote:
| I'd imagine that for the group of people who can see the
| difference, it must be very aggravating - much like when you
| start to see kerning mistakes. For the rest of us, though, it is
| imperceptible.
| bonoboTP wrote:
| Is downscaling difficult? I can understand that upscaling is hard
| and you need learning. But when downscaling, for me OpenCV's
| "area" interpolation always gives great results super fast.
| Sesse__ wrote:
| Is "area" just a box filter, which is what it sounds like? If
| so, it gives really blurry results; hardly great.
| henning wrote:
| I love bagging on lazy engineers who just chuck code over the
| fence without caring about the user experience, but I seriously
| doubt I would notice this. The sad truth is a lot of video is
| watched in the background and Netflix knows this. For the
| specific case of a children's cartoon, I doubt the children
| watching will notice or care.
|
| If there _is_ user feedback about the quality, then by all means
| listen to users and at least have an "advanced settings" menu in
| the app to let users toggle between encoders if they really care.
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