Can someone help me identify my youtube streaming buffering issue

[bheeshmpita]

I stream videos through mpv (generally at 480p at 2x speed). I face buffering issue even at 480p. From what i have found out going through issues at github where downloading videos progresses isp speed while buffers while streaming is that ffmpeg has not implemented workarounds for youtube throttling videos >10MB size. Leaving yt-dlp current issue where all users are facing throttled speeds, i face the previously described problem. Kindly go through log file and help me identify and fix the issue. Here are some system details:

mpv 0.35.1
yt-dlp version 2023.02.17
ffmpeg version 4.4.2-0ubuntu0.22.04.1
OS Linux mint 21 xfce
CPU i3-3110m with igpu

mpvlog.txt

[Traneptora]

yt-dlp recently implemented a fix for the >10MB issue. Update your yt-dlp.

[bheeshmpita]

@thebombzen let me rephrase my issue. I am not downloading videos with yt-dlp instead I am streaming them using mpv. When I download videos they download at full ISP speed but buffers when i stream them (even @ 480/720p). That's the issue I am looking to fix. Kindly go through log text and help me identify the issue and fix it.
I have updated yt-dlp and the issue still persists.

mpvlog.txt
(updated log text with new yt-dlp)

[CounterPillow]

There's no way for you to fix this short of writing code for FFmpeg to make its HTTP implementation do the workarounds to evade youtube's throttling

[bheeshmpita]

@CounterPillow Thanks. Can you help me explain a little bit more what actually is happening and ffmpeg needs to do (in layman terms) and does everyone faces this who streams with mpv?

[eljamm]

This may be related to #10745

Playing video-only formats seems to throttle the speed. Here are some tests that i did:

• 398 (video-only) -> throttled
• 250 (audio-only) -> unthrottled
• 18 (video+audio) -> unthrottled
• 22 (video+audio) -> unthrottled

Merging videos+audio with audio doesn't seem to throttle, but with video-only it does:

• 22+250 -> unthrottled
• bv[height<=?480]+ba -> throttled

Versions:

• yt-dlp: 2023.03.04
• mpv: 0.35.1 + patches from ytdl_hook: init fragment requires other fragments #11398

---

Logs:
398-throttled.txt
250-unthrottled.txt
18-unthrottled.txt
22-unthrottled.txt
22-250-unthrottled.txt
bv-480-ba-throttled.txt

[bheeshmpita]

Thanks so much @eljamm for pointing out this to me as this basically solves my issue else I had the presumption that lower the video quality the less will it be prone to throttling. I have some other queries too, please address them if you have time:

1. I was able to stream video without throttling by giving command from terminal but as i generally dont use terminal to watch videos can you help me by pointing out what I am missing: I tried adding ytdl-format=22 in mpv.conf but no success, tried same in yt-dlp.conf still nothing. so basically it works from terminal but doesnt otherwise.

I had a similar issue earlier where i want to stream videos in h264 but adding stuff to mpv.conf wasnt working but when i added -S "codec:h264" to yt-dlp.conf and then it worked but this time when i add -f 22 to yt-dlp.conf it isnt loading video unthrottled.

2. Can you rephrase the merging audio/video causes crippling bandwidth on YouTube streams #10745 (in easier terms), what I am able to understand is- streaming videos other than 360 and 720p will get throttled as the audio and video file have to be merged instead streaming them collectively. So does that mean if I want to stream in 480p it will throttle?
3. Some easier understanding of  ytdl_hook: init fragment requires other fragments #11398 as i too get these errors and video plays without the audio.
   Thanks again.

Edit: found a solution to point no. 1. where i added --ytdl-format=22 in options>mpv arguments of playwithmpv extension. If you have something else to add on please feel free:)

[eljamm]

2. This is the best comment that I found that describes the issue:
   mpv slow download speed? #8655 (comment)

Only the formats with the https protocol are not throttled, but they can only go up to 720p.
You can find them by using yt-dlp -F <URL>

Also, you can put them in order of preference. If one isn't available it will go to the next:

mpv --ytdl-format="22/18/17/bv+ba" <URL>

---

3. This explanation is not 100% accurate, so please correct me if I'm wrong:

yt-dlp

There are two protocols in yt-dlp for downloading files:

• https: Only one URL is needed.
• dash: Multiple URLs, also called fragments, are needed.

Youtube throttled downloading dash files using the https protocol, which yt-dlp fixed by changing the query¹, but which also caused issues with how mpv handles fragments.

mpv

There are two types of dash fragments:

• init: Contains information about the file
• data: Contains actual media data and the start time to play it (duration)

Before #11398, the first fragment without a duration was considered as init and the ones after it as data:

init + data + data + ...

However, yt-dlp splits fragments as 10MB chunks, so if the filesize is less than 10MB, it would be sent as 1 fragment. As a result, this fragment was considered to be init, and the data was left empty.

( As I understand, durations are used to order fragments, but if there is 1 fragment then this parameter is not included, as it's already in order. )

The fix here is to look for init fragments only if there are more than 1 fragments in total.

fragment + fragment + fragment + ... --> init + data + data + ...

fragment --> data

Without fix

• Stream size >10MB (Usually Video): Played fine, aside from the EDL warnings.
• Stream size <10MB (Usually Audio): Does not play

This explains the videos with no audio.

Applying fix

To apply this yourself, you must add the patched ytdl_hook file to ~/.config/mpv/scripts/².

$ curl https://raw.githubusercontent.com/mpv-player/mpv/362256edbc4f95c63e69c1fa8c8dce9cc6c44288/player/lua/ytdl_hook.lua -o ~/.config/mpv/scripts/ytdl_hook.lua

You might also need to use --ytdl=no as mentioned in the PR.

Footnotes

1. https://github.com/yt-dlp/yt-dlp/issues/6400#issuecomment-1455101468 | https://github.com/yt-dlp/yt-dlp/commit/5038f6d713303e0967d002216e7a88652401c22a ↩

2. https://mpv.io/manual/master/#lua-scripting ↩