No opus sound if youtube-dl -f webm/bestvideo+bestaudio

[megapro17]

When downloading from youtube with vp9/opus, if using
youtube-dl -f webm/bestvideo+bestaudio - completely no sound
In opposition, if using youtube-dl -f mp4/bestvideo+bestaudio sound exists

D:\Users\megapro17\Desktop>youtube-dl -f webm/bestvideo+bestaudio https://www.youtube.com/watch?v=6Dh-RL__uN4
[youtube] 6Dh-RL__uN4: Downloading webpage
[youtube] 6Dh-RL__uN4: Downloading video info webpage
[download] Destination: bitch lasagna-6Dh-RL__uN4.webm
[download] 100% of 34.49MiB in 00:03

D:\Users\megapro17\Desktop>ffmpeg -i "bitch lasagna-6Dh-RL__uN4.webm"
ffmpeg version 4.1.1 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 8.2.1 (GCC) 20190212
Input #0, matroska,webm, from 'bitch lasagna-6Dh-RL__uN4.webm':
  Metadata:
    encoder         : google/video-file
  Duration: 00:02:14.50, start: 0.000000, bitrate: 2151 kb/s
    Stream #0:0(eng): Video: vp9 (Profile 0), yuv420p(tv, bt709), 1920x1080, SAR 1:1 DAR 16:9, 29.97 fps, 29.97 tbr, 1k tbn, 1k tbc (default)
At least one output file must be specified

D:\Users\megapro17\Desktop>

This bug not appearing on old vp8/vorbis videos

> py -2.7 .\youtube_dl\__main__.py  BaW_jenozKc -f webm/bestvideo+bestaudio
[youtube] BaW_jenozKc: Downloading webpage
[youtube] BaW_jenozKc: Downloading video info webpage
[download] Destination: youtube-dl test video ''_-BaW_jenozKc.webm
[download] 100% of 181.60KiB in 00:01

> ffmpeg.exe -i '.\youtube-dl test video ''''_-BaW_jenozKc.webm'
ffmpeg version N-85653-gb4330a0 Copyright (c) 2000-2017 the FFmpeg developers
Input #0, matroska,webm, from '.\youtube-dl test video ''_-BaW_jenozKc.webm':
  Metadata:
    encoder         : google
  Duration: 00:00:09.93, start: 0.000000, bitrate: 149 kb/s
    Stream #0:0(eng): Video: vp8, yuv420p(progressive), 640x360, SAR 1:1 DAR 16:9, 1k fps, 30 tbr, 1k tbn, 1k tbc (default)
    Stream #0:1: Audio: vorbis, 44100 Hz, stereo, fltp (default)
At least one output file must be specified

I have found some workaround, if type youtube-dl -f bestvideo[ext=webm]+bestaudio it downloads normally with sound.

серёга не закрывай

[dstftw]

This is expected behavior for your format selector since 6Dh-RL__uN4 has no audiovideo formats with webm extension thus video-only webm is downloaded.