[Question] odd ba* format selection?

[probablykasper]

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Question

I'm running the following command:

yt-dlp -x -f 'ba*' --format-sort 'abr,codec' 'https://www.youtube.com/watch?v=nzLw6GMQ65I'

As a result, I get a 2.9MB .m4a file. When I pass -F it shows an ABR of 0k (format ID 22).

If I instead use -f 'ba', I get 3.3MB .opus file. Shouldn't ba* have selected this .opus file to begin with, since it's larger?

[pukkandan]

I can see why you would think that. But

• ba, bestaudio: Select the best quality audio-only format. Equivalent to best*[vcodec=none]
• ba*, bestaudio*: Select the best quality format that contains audio. It may also contain video. Equivalent to best*[acodec!=none]

ba* is NOT "select the format that contains the best quality audio"

A format that contains a video stream is always considered better by yt-dlp than a format without it. Since 22 contains both an audio and a video stream, it is considered better than all audio-only streams. Hence why 22 gets selected. Hopefully I explained this clearly

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But the more important question is how do you select "the format that contains the best audio"?

In theory, you can achieve this by asking yt-dlp to not consider video streams to be always better than audio-only (which is controlled by the sorting parameter hasvid) by using --format-sort-force. So --format-sort-force -S "abr,acodec" will give you what you want.

BUT, as you have already noticed, yt-dlp shows the abr of format 22 as 0k. This is because we do not know the vbr and abr of this format, but only know the tbr. For simplicity, this tbr is shown in the vbr column when listing formats, with abr set to 0. This means we do not know what is the sound quality of this format and so will sort it with least priority when using the above method. So, this becomes the equivalent of just using -S abr -f ba

tldr; you can't for sure. Just use ba to get the best with the limited information we have

[probablykasper]

Ah I see, that explains it really well. Thanks!

[probablykasper]

Looks like the actual flag is --format-sort-force, not -force-format-sort like it mentions in the "Sorting Format" section in the docs

[pukkandan]

thanks I'll fix it