-postprocessor-args Applied Multiple Times

[antgiant]

Checklist

• I'm reporting a broken site support issue
• I've verified that I'm running youtube-dl version 2020.09.20
• 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

youtube-dl -f bestaudio --extract-audio --audio-format mp3 -o "Testing.%(ext)s"  --embed-thumbnail --add-metadata --postprocessor-args "-ss 46:01 " "https://vimeo.com/464541793" --verbose
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['-f', 'bestaudio', '--extract-audio', '--audio-format', 'mp3', '-o', 'Testing.%(ext)s', '--embed-thumbnail', '--add-metadata', '--postprocessor-args', '-ss 46:01 ', 'https://vimeo.com/464541793', '--verbose']
[debug] Encodings: locale cp1252, fs mbcs, out cp437, pref cp1252
[debug] youtube-dl version 2020.09.20
[debug] Python version 3.4.4 (CPython) - Windows-10-10.0.17763
[debug] exe versions: ffmpeg 2020-10-07-git-a086b73e1f-essentials_build-www.gyan.dev, ffprobe 2020-10-07-git-a086b73e1f-essentials_build-www.gyan.dev
[debug] Proxy map: {}
[vimeo] 464541793: Downloading webpage
[vimeo] 464541793: Extracting information
[vimeo] 464541793: Downloading JSON metadata
[vimeo] 464541793: Downloading JSON metadata
WARNING: Unable to download JSON metadata: HTTP Error 403: Forbidden
[vimeo] 464541793: Downloading akfire_interconnect_quic m3u8 information
[vimeo] 464541793: Downloading akfire_interconnect_quic m3u8 information
[vimeo] 464541793: Downloading fastly_skyfire m3u8 information
[vimeo] 464541793: Downloading fastly_skyfire m3u8 information
[vimeo] 464541793: Downloading akfire_interconnect_quic MPD information
[vimeo] 464541793: Downloading akfire_interconnect_quic MPD information
[vimeo] 464541793: Downloading fastly_skyfire MPD information
[vimeo] 464541793: Downloading fastly_skyfire MPD information
[vimeo] 464541793: Downloading thumbnail ...
[vimeo] 464541793: Writing thumbnail to: Testing.jpg
[debug] Invoking downloader on 'https://skyfire.vimeocdn.com/1602399887-0x309c3f8c9348306fbccb28e57078997b9fafbfec/3d60fe57-3444-49d0-b21d-ab5e3fc42b85/sep/video/7ce39f59,a390af55,b05423e8,c49277e9,620496d1/master.mpd?base64_init=1'
[dashsegments] Total fragments: 909
[download] Destination: Testing.m4a
[download] 100% of 165.86MiB in 04:45
[ffmpeg] Correcting container in "Testing.m4a"
[debug] ffmpeg command line: ffmpeg -y -loglevel "repeat+info" -i "file:Testing.m4a" -c copy -f mp4 -ss "46:01" "file:Testing.temp.m4a"
[debug] ffmpeg command line: ffprobe -show_streams "file:Testing.m4a"
[ffmpeg] Destination: Testing.mp3
[debug] ffmpeg command line: ffmpeg -y -loglevel "repeat+info" -i "file:Testing.m4a" -vn -acodec libmp3lame "-q:a" 5 -ss "46:01" "file:Testing.mp3"
Deleting original file Testing.m4a (pass -k to keep)
[ffmpeg] Adding metadata to 'Testing.mp3'
[debug] ffmpeg command line: ffmpeg -y -loglevel "repeat+info" -i "file:Testing.mp3" -c copy -metadata "date=20201003" -metadata "title=2020-10-10 - Tabernacling with God by Pastor Chandler Tarbox" -metadata "comment=The weekly Livestream of the Spring Meadows SDA church." -metadata "purl=https://vimeo.com/464541793" -metadata "description=The weekly Livestream of the Spring Meadows SDA church." -metadata "artist=Spring Meadows SDA" -ss "46:01" "file:Testing.temp.mp3"
ERROR: file:Testing.mp3: Invalid argument
Traceback (most recent call last):
  File "C:\Users\dst\AppData\Roaming\Build archive\youtube-dl\ytdl-org\tmpksi3o1r1\build\youtube_dl\YoutubeDL.py", line 2065, in post_process
  File "C:\Users\dst\AppData\Roaming\Build archive\youtube-dl\ytdl-org\tmpksi3o1r1\build\youtube_dl\postprocessor\ffmpeg.py", line 509, in run
  File "C:\Users\dst\AppData\Roaming\Build archive\youtube-dl\ytdl-org\tmpksi3o1r1\build\youtube_dl\postprocessor\ffmpeg.py", line 235, in run_ffmpeg_multiple_files
youtube_dl.postprocessor.ffmpeg.FFmpegPostProcessorError: file:Testing.mp3: Invalid argument

Description

I am attempting to accomplish downloading a part of a video. Since #622 makes it clear there is not currently support for that I have attempted to use the -postprocessor-args option to pass in a start time (-ss). However, that command is then applied twice completely breaking it as it doubles the amount cut off the front and just breaks the the -to command completely.
Here is the relevant part of the full log

[ffmpeg] Correcting container in "Testing.m4a"
[debug] ffmpeg command line: ffmpeg -y -loglevel "repeat+info" -i "file:Testing.m4a" -c copy -f mp4 -ss "46:01" "file:Testing.temp.m4a"
[debug] ffmpeg command line: ffprobe -show_streams "file:Testing.m4a"
[ffmpeg] Destination: Testing.mp3
[debug] ffmpeg command line: ffmpeg -y -loglevel "repeat+info" -i "file:Testing.m4a" -vn -acodec libmp3lame "-q:a" 5 -ss "46:01" "file:Testing.mp3"

I also tried the --external-downloader-args method described in #12347 and those args were completely ignored, resulting in full length download.

While for me this breaks trimming it would also break a number of other uses for -postprocessor-args as it will double up any processing done via -postprocessor-args.

[october262]

see this thread - https://unix.stackexchange.com/questions/230481/how-to-download-portion-of-video-with-youtube-dl-command

[antgiant]

see this thread - https://unix.stackexchange.com/questions/230481/how-to-download-portion-of-video-with-youtube-dl-command

I did. In fact my command is pretty much a directly this answer from that thread. I also mentioned trying --external-downloader-args. That was me trying to turn the first several answers on the thread you mentioned into a single command. but it seems that is broken in youtube-dl at the moment as well.

Either way I consider it a bug that -postprocessor-args are applied twice. Far more that just my particular use case will be negatively impacted by that.

[dstftw]

This is expected behavior, --postprocessor-args is applied to each post processor.