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!
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.
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
The reason for why I think it said usually considered transparent is because when you have a less busy track it sounds transparent and I think its from the perspective of the average end user.