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Tips on yt-dlp and YouTube audio quality? (lemmy.ml)

submitted 4 months ago by [email protected] to c/[email protected]

8 comments fedilink hide all child comments

Hi friends,

I've been using yt-dlp to download a few things off of YouTube Music, and I just wanted to ask a few questions about best practice. Right now, I've just been doing it this way:

yt-dlp -f bestaudio -x

I've found that has usually downloaded .opus files (though, .m4a as of late—anyone know why this is?), but, I was wondering (for the sake of compatibility with different music players), do I lose anything by passing --recode mp3?

Also, about losing the .opus files, I got this output when I ran yt-dlp -F on a link:

|ID |  EXT   RESOLUTION FPS CH |    FILESIZE  TBR PROTO | VCODEC         VBR ACODEC      ABR ASR MORE INFO
--------------------------------------------------------------------------------------------------------------------------
233 mp4   audio only        |                  m3u8  | audio only         unknown             Default
234 mp4   audio only        |                  m3u8  | audio only         unknown             Default
249 webm  audio only      2 |     1.30MiB  64k https | audio only         opus        64k 48k low, THROTTLED, webm_dash
250 webm  audio only      2 |     1.64MiB  81k https | audio only         opus        81k 48k low, THROTTLED, webm_dash
139 m4a   audio only      2 |  1019.36KiB  49k https | audio only         mp4a.40.5   49k 22k low, m4a_dash
251 webm  audio only      2 |     3.03MiB 149k https | audio only         opus       149k 48k medium, THROTTLED, webm_dash
140 m4a   audio only      2 |     2.64MiB 130k https | audio only         mp4a.40.2  130k 44k medium, m4a_dash

Any insights as to why I'm getting that throttling, and why it's downloading m4a instead of opus? Is it even that much of a difference? Is there some option I can pass to yt-dlp to avoid this?

Any help is much appreciated!

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[–] [email protected] 19 points 4 months ago (1 children)

Transcoding from one lossy codec to another just reduces the quality even more. You can transcode to wave or flac, but that will just increase the file size.

There won't be much of a quality difference between opus and mp4. If the music was uploaded at 44.1K, the mp4 will be higher quality even though the bitrate is slightly lower since the opus would be resampled to 48K.

[–] Supermariofan67 7 points 4 months ago* (last edited 4 months ago) (1 children)

Resampling does not lead to any perceptible quality loss, but encoding to aac with libavcodec's encoder (as YouTube does) definitely will. At the very least, it cuts all frequencies above 15 kHz which are potentially audible. Opus does not, and 128k opus is usually considered transparent.

I can't find it but somewhere there's a very detailed explanation from Monty himself about it

[–] Supermariofan67 13 points 4 months ago

Are you using the very latest version? YouTube changed their site again a few days ago and it broke yt-dlps ability to find all thr formats. Update yt-dlp and it should be back to normal. yt-dlp will prefer the opus when it is available by default.

Opus is much better than (YouTube's) m4a. m4a is better than mp3 (which is an obsolete 30 year old format). YouTube doesn't serve mp3 (so creating one means re-encoding), and re-encoding lossy formats always loses quality.

[–] [email protected] 5 points 4 months ago

Youtubes Audio quality is pretty terrible in general. Dont think you'll lose too much

[–] [email protected] 2 points 4 months ago

I don't think opus can be stored in an mp3 container without reencoding. Opus can be stored in mkv, ogg (or opus, an alias of the ogg file format, unless that changed), mp4 (I think this may be experimental?), and webm, off the top of my head. Try using ffmpeg to copy to various formats: ffmpeg -i in.opus -c copy out.ext, replacing ext with whatever file format you need. -c copy will always be lossless.

You can also try reencoding as flac or another lossless audio codec, but this may balloon your file size.

[–] [email protected] 1 points 4 months ago (1 children)

It's probably deciding what the best audio is by bitrate (file size) instead of codec.

[–] Supermariofan67 3 points 4 months ago

This would not be the default behavior of yt-dlp. Run yt-dlp -vF <video> to view the sort order used. Acodec should come before abr.

It used to be the behavior of the original youtube-dl, however.