[AltruisticGapHN]

I'm "eyeballing" switching between Infuse and YouTube on an Apple TV 4k 2nd Gen (2021). The Sony TV is 1080p but I've been chosing 1440p now in YouTube as it definitely looks better overall (more details).

The downloaded video is also 1440p, same audio/video streams as far I can tell. So both Infuse and YouTube will do some scaling to the viewport 1440 > 1080p.

This is an example video:

https://www.youtube.com/watch?v=-VE-tgVOZN8&t=3m30s

So the left side is really dark and that's the area where you'd typically see more compression artifacts right? Due to the algorithm thinking there's no detail there. So in YouTube it feels solid. But in Infuse I notice tiny little jitters there and it just distracts and I'm guessing it's those really subtle "grainy" things that take away from the picture feeling really clean and smooth.

Now when I switch back to YouTube and I really look for it, at same time stamp I can notice some artifacts, but it's just not as noticable... so I'm still wondering what is going on. Does YouTube also do some kinda brightness/contrast filter perhaps similar to audio? Due to playing back on a TV maybe?

Without being able to make screenshots it's really hard to tell since the time it takes to switch between the apps you get flashes or brightness/dark and the eyes are affected by it. All I can tell is in YouTube the picture just feels smoother and cleaner overall.

edit:

Another example gives some hitns perhaps

https://www.youtube.com/watch?v=-VE-tgVOZN8&t=6m32s

So now I am checking out the video on my desktop linux with a 1440p monitor, in YoUTube and in VLC player (Ubuntu, AMD GPU).

So interestingly in the background behind Ally to the left on VLC you can clearly see the banding of blue colours, there are lots of squares which are jittering, like the fuzzy grain on a night cam. It's really distracting.

In YouTube (same desktop, via Google Chrome), there is colour banding in the blue background to the left of Ally, but it is not as noticeable because it's like the squares have been averaged and the edge of the bands is smoother. While you can see some tiny shaking there in the colour bands if you look for it, it is not distracting from the overall image.

Hmm.

UPDATE /SOLVED?

Ok after redownloading 1440p 271 stream (VP9) I can confirm the color banding is the "smooth" one I saw in YouTube.

Something's fishy with YouTube I did download the VP9 codec ~3 weeks ago and since then they have changed the streams and the bitrates are lower. There are these new "6xx" streams while the old 1xx/2xx streams appear to have a lower filesize.

But oddly enough the 400 MB filesize I just downloaded has the smoother nicer picture, whereas the 500 MB file I downloaded weeks ago, has the squares/fuzzy/grainy effect. VLC tells me both are VP9 so hmm.

[mgdlbp]

Ah that makes sense - the first video was only uploaded 3 weeks ago. It's known that, on youtube, formats become available in increasing resolution after upload as they finish encoding. Your experience now shows that the higher-res streams are encoded in a rush at first and later replaced with better compressed versions.

.

I've never seen such a long format list in youtube-dl before. Are 6xx new? Apparently,[1] they were introduced together with that 'premium 1080p' this April.

Comparing older 4k videos to your video: this one[2] now has 6xx, and 4xx are gone, and curiously the reported bitrates of all streams have since changed (reencoded?). 137 stayed about the same this time, but 18 dropped from 730k to 493k. For this video[3] 4xx are still available.

.

616 is not the actual premium 1080p as the posters at [4] think, is it? Currently youtube.com chooses 248 when playing [2], but yt-dlp can list and download 614 and 616 without any account cookies.

Rather, 6xx seem to comprise (of) vp9 spanning a medium, high, and sometimes low bitrate in all resolutions. Is yt considering replacing the older formats with these?

I just hope the original 18 and 22 remain for older videos, where any difference in quality also matters the most. When still available, in most cases the H.264 streams with creation_time prior to ~2013 are dramatically clearer than any more recent formats.

[1] https://github.com/yt-dlp/yt-dlp/issues?q=605+604+603+sort%3...

[2] https://github.com/yt-dlp/yt-dlp/issues/1863#issue-106877303...

[3] https://github.com/yt-dlp/yt-dlp/issues/389#issuecomment-103...

[4] https://github.com/yt-dlp/yt-dlp/issues/6770

lets not discuss how often the h264 streams for new videos are higher quality than the vp9

[bavell]

Have you used `mediainfo` to check the codecs, bitrate and encoding settings? Curious what you'd find there...

[AltruisticGapHN]

Hey thanks I didn't know about this tool.

Interestingly since I have the older download from ~3 weeks ago I just ran mediainfo on it, and the new download from today. Then I just switch tabs in terminal so I can easily see what changes.

Old / New

    vp09 / vp09 

    filesize   488 mb   / 391 mb

    OVerall bitrate   3274 kb/s   /  2620 kb/s

    Bits/(Pixel\*Frame)    0.036 / 0.028

I don't see anything else significant.

It seems to me in recent weeks YouTube has changed the streams, added new "high bitrate Premium" streams (edit: WHILE lowering the bitrate on the older existing streams like 137!), and perhaps the one I downloaded earlier, despite being a larger filesize, was not encoded correctly?

The new file despite being 20% smaller (~400 mb instead of 500), has the smoother color banding, and doesn't show the ugly jittery grainy artifacts.

I used to think larger filesize is better but I guess Iḿ going to get the Vp9 from now on...

[ubercow13]

I have noticed that Youtube often re-encodes videos, replacing the data for a certain stream type/number with a new encode.

[AltruisticGapHN]

Yes that is probably what it was!

I'll remember that even two+ days after the initial upload, there may still be reencoding. I thought this was only few hours after the creator uploads.

So the smaller filesize also is not necessarily a sign of lower quality. In this case it's because it gets a quick first encoding like zip with fast compression, and then it gets reencoded presumably by something much more CPU intensive.

That said from 500mb to 400mb is a bit dodgy but what do I know maybe VP9 is that good.

[bavell]

Interesting! Thanks for running mediainfo on them to compare.

When encoding videos there's a "speed" parameter that basically tells the encoder to spend more CPU time compressing the frames. It results in a smaller output size while maintaining the same level of quality but takes much longer to encode. I'm sure that's part of what YT is doing here, an initial quick encode to get the video live then another pass to reduce filesize for long term storage. Good find!

I'm guessing that the perceived higher quality in the smaller file is because the encoder was able to find a more accurate way to represent those frames with the same or fewer number of bits since it has more time to search for the optimal encoding.