-f bestvideo doesn't always download best quality video from Youtube.

[ilovelinux]

Checklist

• I'm reporting a broken site support issue
• I've verified that I'm running youtube-dl version 2020.03.24
• I've checked that all provided URLs are alive and playable in a browser
• I've checked that all URLs and arguments with special characters are properly quoted or escaped
• I've searched the bugtracker for similar bug reports including closed ones
• I've read bugs section in FAQ

Description

Video: https://www.youtube.com/watch?v=GTcM7ydgAwo
Command: youtube-dl -f bestvideo https://www.youtube.com/watch?v=GTcM7ydgAwo

Today I was downloading that video from Youtube. I thought that -f bestvideo would have considered the video encoding but it doesn't seem to do it. In fact that video has a lot of differen formats but we will focus on the best two:

248          webm       1920x1080  1080p 2642k , vp9, 30fps, video only, 89.18MiB
137          mp4        1920x1080  1080p 4330k , avc1.640028, 30fps, video only, 82.31MiB

Webm has lower bitrate because it uses vp9 and it should be bettter than 137 but youtube-dl chose 137.

I would expect -f bestvideo to choose the webm since it's heavier and it's encoded with vp9 instead of mp4.

[Hrxn]

You must put something like this into your youtube-dl.conf:

--format "(bestvideo[vcodec=vp9.2]/bestvideo[vcodec=vp9][fps>30]/bestvideo[vcodec=vp9][height>=1080]/bestvideo[fps>30]/bestvideo[height>720])+(bestaudio[acodec=opus]/bestaudio)/best"

This enforces preference for VP9

Edit

I would expect -f bestvideo to choose the webm since it's heavier and it's encoded with vp9 instead of mp4.

You're obviously right, but just look at the two listed formats in your example above. Compare file size and bitrate, this does not make really sense, but that's what is returned by YT. Apparently not always correct.

[ilovelinux]

I did know how to force vp9 codec, I was just reporting that even if VP9 encoded file is smaller and has lower bitrate, should be preferred to AV1. Thank you anyway!

[Hrxn]

Preferred to MP4/AVC you mean?

But otherwise I agree, the automatic format selection should maybe updated so that VP9 takes precedence, after all it's the preferred format by YouTube as well, and while transition has been slow, it's the better optimized format for now..