bestvideo by codec and bitrate

[suuuehgi]

Checklist

• I'm reporting a feature request
• I've verified that I'm running youtube-dl version 2020.09.14
• I've searched the bugtracker for similar feature requests including closed ones

Description

At the moment youtube-dl -f bestvideo results in the AVC / H.264 version being downloaded.

This is certainly the best possible video quality. But since YT (nearly always*) encodes with constant quality per resolution, we might as well take another format without loosing quaity.**

I would hence argue that bestvideo is the one with the smallest file size of the ones with the highest quality.

I would hence like to propose the following for bestvideo:

1. Search for the highest resolution
2. 2.1 Choose the first existing codec along this scheme: AV1 --> VP9 --> AVC
   2.2 If multiple qualities are available for the same codec, choose the one with the highest bitrate.*

This would also avoid verbose constructs like:

-f 'bestvideo[vcodec *= av01]+bestaudio/bestvideo[vcodec *= vp9]+bestaudio/bestvideo+bestaudio/best'

Thanks a lot!

MWE

youtube-dl -f bestvideo ibXKKllz4xQ

[...]
399          mp4        1920x1080  1080p 2450k , av01.0.08M.08, 30fps, video only, 187.14MiB
248          webm       1920x1080  1080p 2645k , vp9, 30fps, video only, 178.88MiB
137          mp4        1920x1080  1080p 3072k , avc1.640028, 30fps, video only, 140.01MiB
[...]

results in format 137.

---

* youtube-dl -F QPdWJeybMo8

[...]
402          mp4        7680x4320  4320p 22458k , av01.0.16M.08.0.110.01.06.06.0, 30fps, video only, 367.57MiB
571          mp4        7680x4320  4320p 36937k , av01.0.16M.08.0.110.01.06.06.0, 30fps, video only, 582.34MiB
[...]

** Since this is logically not bullet-proof, we might as well generally assume AV1 > VP9 > AVC.

[suuuehgi]

Could you point me to the issue where this is a duplicate of? I now spent 5 min searching without a hit. Thank you!