[FFmpeg-trac] #10739(undetermined:new): Weird behavior of aresample filter in the presence of -map argument

[FFmpeg]

#10739: Weird behavior of aresample filter in the presence of -map argument
-------------------------------------+-------------------------------------
             Reporter:  bubbleguuum  |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 There is a weird difference of behavior between FFmpeg 5 and 6 when the
 aresample filter is used in conjunction with -map argument.
 Here converting a mp3 to WAV with resampling. It is not super useful, but
 for illustration purpose and the input and output codecs are not relevant.

 FFmpeg 6 fails:

 {{{

 % ffmpeg -hide_banner -y -i ~/Music/audio\ formats/MP3_192K.mp3  -map 0:0
 -filter_complex aresample=resampler=soxr ~/tmp/file.wav
 Input #0, mp3, from '/home/bobbie/Music/audio formats/MP3_192K.mp3':
   Duration: 00:03:54.08, start: 0.025057, bitrate: 192 kb/s
   Stream #0:0: Audio: mp3, 44100 Hz, stereo, fltp, 192 kb/s
     Metadata:
       encoder         : LAME3.93
 Stream mapping:
   Stream #0:0 (mp3float) -> aresample:default (graph 0)
   aresample:default (graph 0) -> Stream #0:0 (pcm_s16le)
   Stream #0:0 -> #0:1 (mp3 (mp3float) -> pcm_s16le (native))
 Press [q] to stop, [?] for help
 [wav @ 0x55c1836f7a80] WAVE files have exactly one stream
 [out#0/wav @ 0x55c1836f7980] Could not write header (incorrect codec
 parameters ?): Invalid argument
 [aost#0:1/pcm_s16le @ 0x55c183704800] Error initializing output stream:
 Conversion failed!

 }}}


 FFmpeg 5 works

 {{{
 % ffmpeg -hide_banner -y -i ~/Music/audio\ formats/MP3_192K.mp3  -map 0:0
 -filter_complex aresample=resampler=soxr ~/tmp/file.wav
 Input #0, mp3, from '/home/bobbie/Music/audio formats/MP3_192K.mp3':
   Duration: 00:03:54.08, start: 0.025057, bitrate: 192 kb/s
   Stream #0:0: Audio: mp3, 44100 Hz, stereo, fltp, 192 kb/s
     Metadata:
       encoder         : LAME3.93
 Stream mapping:
   Stream #0:0 (mp3float) -> aresample:default
   aresample:default -> Stream #0:0 (pcm_s16le)
 Press [q] to stop, [?] for help
 Output #0, wav, to '/home/bobbie/tmp/file.wav':
   Metadata:
     ISFT            : Lavf59.16.100
   Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, stereo,
 s16, 1411 kb/s
     Metadata:
       encoder         : Lavc59.18.100 pcm_s16le
 size=   40317kB time=00:03:54.04 bitrate=1411.2kbits/s speed= 389x
 video:0kB audio:40317kB subtitle:0kB other streams:0kB global headers:0kB
 muxing overhead: 0.000189%
 }}}


 For some reason, FFmpeg 6 creates 2 output streams when -map and aresample
 are used at the same time, while FFmpeg 5 creates 1 output which I what I
 would expect. The former makes writing the output file fail because the
 format (WAV but could also be FLAC) expects exactly 1 output audio stream.

 What is the reason for this and is it a regression ?
 Not specifying -map 0:0 fixes it, but I'd like to understand this change
 in behavior between FFmpeg 5 and 6.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/10739>
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