Incorrect parameters passed to ffmpeg for some youtube videos when extracting audio

[RasmusMathiesen]

Checklist

• I'm reporting a broken site support
• I've verified that I'm running youtube-dl version 2020.01.24
• 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

Verbose log

PS C:\Users\rasmu\Desktop\youtube test\ffmpeg test> youtube-dl --format "bestaudio" --extract-audio --audio-format "opus" --audio-quality "32K" -v -k sZlzYzyREAI
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['--format', 'bestaudio', '--extract-audio', '--audio-format', 'opus', '--audio-quality', '32K', '-v', '-k', 'sZlzYzyREAI']
[debug] Encodings: locale cp1252, fs utf-8, out utf-8, pref cp1252
[debug] youtube-dl version 2020.01.24
[debug] Python version 3.8.1 (CPython) - Windows-10-10.0.18362-SP0
[debug] exe versions: ffmpeg 4.2.1, ffprobe 4.2.1
[debug] Proxy map: {}
[youtube] sZlzYzyREAI: Downloading webpage
[youtube] sZlzYzyREAI: Downloading video info webpage
[debug] Invoking downloader on 'https://r2---sn-uqj-j2iz.googlevideo.com/videoplayback?expire=1580151038&ei=ntwuXoDTKouw7ASb2ZioDA&ip=85.129.39.156&id=o-AC8oimTbXK1hrX6ldL4tBRW9GcZQC0Vk7ITr4yuocT6N&itag=251&source=youtube&requiressl=yes&mm=31%2C29&mn=sn-uqj-j2iz%2Csn-5goeen7y&ms=au%2Crdu&mv=m&mvi=1&pcm2cms=yes&pl=24&initcwndbps=1946250&vprv=1&mime=audio%2Fwebm&gir=yes&clen=3052076&dur=179.981&lmt=1577947661429043&mt=1580129298&fvip=2&keepalive=yes&fexp=23842630&c=WEB&txp=6531432&sparams=expire%2Cei%2Cip%2Cid%2Citag%2Csource%2Crequiressl%2Cvprv%2Cmime%2Cgir%2Cclen%2Cdur%2Clmt&sig=ALgxI2wwRgIhANZsUUKYO2cMcsbiKeP3rv4oVx6Yo9rdYm0r-0LLjVDlAiEAqq_ZjgmzRFyLzVqoFfDl7F4VM3PUQpsHX0m-tq5JqIM%3D&lsparams=mm%2Cmn%2Cms%2Cmv%2Cmvi%2Cpcm2cms%2Cpl%2Cinitcwndbps&lsig=AHylml4wRQIgRrn29VzcA3J6XnDE8v_FMXFTlQqtAlf1vc_vav4clDMCIQD-k0gXKMYC-BEOHCVoKTQkxpIhgakdC5G4gnbcO_FwjA%3D%3D&ratebypass=yes'
[download] Destination: Crew Dragon Animation-sZlzYzyREAI.webm
[download] 100% of 2.91MiB in 00:00
[debug] ffmpeg command line: ffprobe -show_streams "file:Crew Dragon Animation-sZlzYzyREAI.webm"
[ffmpeg] Destination: Crew Dragon Animation-sZlzYzyREAI.opus
[debug] ffmpeg command line: ffmpeg -y -loglevel "repeat+info" -i "file:Crew Dragon Animation-sZlzYzyREAI.webm" -vn -acodec copy "file:Crew Dragon Animation-sZlzYzyREAI.opus"


PS C:\Users\rasmu\Desktop\youtube test\ffmpeg test> youtube-dl --format "bestaudio" --extract-audio --audio-format "opus" --audio-quality "32K" -v -k _yDZY5_u8FQ
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['--format', 'bestaudio', '--extract-audio', '--audio-format', 'opus', '--audio-quality', '32K', '-v', '-k', '_yDZY5_u8FQ']
[debug] Encodings: locale cp1252, fs utf-8, out utf-8, pref cp1252
[debug] youtube-dl version 2020.01.24
[debug] Python version 3.8.1 (CPython) - Windows-10-10.0.18362-SP0
[debug] exe versions: ffmpeg 4.2.1, ffprobe 4.2.1
[debug] Proxy map: {}
[youtube] _yDZY5_u8FQ: Downloading webpage
[youtube] _yDZY5_u8FQ: Downloading video info webpage
[debug] Invoking downloader on 'https://r4---sn-uqj-j2iz.googlevideo.com/videoplayback?expire=1580151130&ei=-twuXs-3C5ijyQX07pHIAg&ip=85.129.39.156&id=o-AMsz9Kozz0cklMoCv5UuZLx2iPbjdTzTY7wBScvUuuGJ&itag=258&source=youtube&requiressl=yes&mm=31%2C29&mn=sn-uqj-j2iz%2Csn-5goeen7y&ms=au%2Crdu&mv=m&mvi=3&pl=24&initcwndbps=1941250&vprv=1&mime=audio%2Fmp4&gir=yes&clen=3266848&dur=67.370&lmt=1579640280116448&mt=1580129455&fvip=4&keepalive=yes&fexp=23842630&c=WEB&txp=1311222&sparams=expire%2Cei%2Cip%2Cid%2Citag%2Csource%2Crequiressl%2Cvprv%2Cmime%2Cgir%2Cclen%2Cdur%2Clmt&sig=ALgxI2wwRgIhAKt9kOSsSg1xjFDzUx-d8oxIMdZauKt6AappqL5PB0M8AiEAhS-6uMZv6qiCHjC3EucyX8ffSXf-LlnU55zgk4IumP8%3D&lsparams=mm%2Cmn%2Cms%2Cmv%2Cmvi%2Cpl%2Cinitcwndbps&lsig=AHylml4wRQIgfSn1ClMl4BI0jGOlLNyzay1f56nqF-j6xl-gof9pJkQCIQDs-6cYSmOzhZb4I0XpIOZETk70kIoz78gk8MFZ-PqGGA%3D%3D&ratebypass=yes'
[download] Destination: Why Does Space Inspire Us Elon Musk-_yDZY5_u8FQ.m4a
[download] 100% of 3.12MiB in 00:00
[ffmpeg] Correcting container in "Why Does Space Inspire Us Elon Musk-_yDZY5_u8FQ.m4a"
[debug] ffmpeg command line: ffmpeg -y -loglevel "repeat+info" -i "file:Why Does Space Inspire Us Elon Musk-_yDZY5_u8FQ.m4a" -c copy -f mp4 "file:Why Does Space Inspire Us Elon Musk-_yDZY5_u8FQ.temp.m4a"
[debug] ffmpeg command line: ffprobe -show_streams "file:Why Does Space Inspire Us Elon Musk-_yDZY5_u8FQ.m4a"
[ffmpeg] Destination: Why Does Space Inspire Us Elon Musk-_yDZY5_u8FQ.opus
[debug] ffmpeg command line: ffmpeg -y -loglevel "repeat+info" -i "file:Why Does Space Inspire Us Elon Musk-_yDZY5_u8FQ.m4a" -vn -acodec libopus "-b:a" 32k "file:Why Does Space Inspire Us Elon Musk-_yDZY5_u8FQ.opus"

Description

When youtube-dl is given these options:

--format "bestaudio" --extract-audio --audio-format "opus" --audio-quality "32K" -v -k

The parameters passed to ffmpeg are not the same for every youtube video when the same parameters are expected:

Expected ffmpeg parameters: (-acodec libopus "-b:a" 32k) (youtube-id "_yDZY5_u8FQ")

[debug] ffmpeg command line: ffmpeg -y -loglevel "repeat+info" -i "file:Why Does Space Inspire Us Elon Musk-_yDZY5_u8FQ.m4a" -vn -acodec libopus "-b:a" 32k "file:Why Does Space Inspire Us Elon Musk-_yDZY5_u8FQ.opus"

Unexpected ffmpeg parameters: (-acodec copy) (youtube-id "sZlzYzyREAI")

[debug] ffmpeg command line: ffmpeg -y -loglevel "repeat+info" -i "file:Crew Dragon Animation-sZlzYzyREAI.webm" -vn -acodec copy "file:Crew Dragon Animation-sZlzYzyREAI.opus"

[RasmusMathiesen]

I think I have identified the problem to be this line:

youtube-dl/youtube_dl/postprocessor/ffmpeg.py

Line 277 in 8e4d3f8

if self._preferredcodec == 'best' or self._preferredcodec == filecodec or (self._preferredcodec == 'm4a' and filecodec == 'aac'):

If the codec of the downloaded file (filecodec) is the same as the preferred codec (self._preferredcodec) then it doesn't matter if a preferred quality is specified, ffmpeg will be told to just copy the stream.

I don't think anyone expects this behaviour when passing a preferred quality, but in case someone currently relies on this behavior the best solution may be to add an option to always force re-encoding, and maybe an option to only convert if the downloaded file has a higher bitrate than preferred.

Currently this behaviour is undocumented so I'm not sure if it is intended or not. Regardless, I suggest officially labeling the current behaviour a feature and adding it to the documentation, and then adding a --force-conversion option. Who will make that decision or how can I request a decision be made about that?

[dstftw]

This is expected behavior. Conversion only happens when source and target formats are different.