[FFmpeg-trac] #9755(undetermined:new): gapless playback of *some* MP3 files destroyed

FFmpeg trac at avcodec.org
Wed Mar 1 01:58:02 EET 2023

#9755: gapless playback of *some* MP3 files destroyed
             Reporter:  Christoph    |                    Owner:  (none)
  Anton Mitterer                     |
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
                                     |  undetermined
              Version:  unspecified  |               Resolution:
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
Comment (by Christoph Anton Mitterer):

 Hey Balling.

 First, please have a look at the messages starting with:

 A while ago (April last year) I've had that re-checked and it seemed at
 first that now it works.
 However, I then checked it again with the very same (gapless) WAV files
 that I've had used in the beginning... and with them I still heard some
 distortion (a tiny but audible pop).

 So conclusion from that is, that it seems to depend on the source file,
 whether it works or not.

 I've just repeated the test with versions as of current Debian unstable,
 that is:
 lame 3.100
 mpv 0.35.1
 ffmpeg 5.1.2

 First I take my original WAVs, encode them with lame via:
 lame --verbose -q 0 -v -V 4 --noreplaygain --id3v2-utf16 --add-id3v2
 --id3v1-only a.wav
 lame --verbose -q 0 -v -V 4 --noreplaygain --id3v2-utf16 --add-id3v2
 --id3v1-only a.wav

 Then I check whether the resulting MP3s play back gaplessly (with no
 mpv a.mp3 b.mp3
 => that works (or at least I cannot hear anything).

 Then I do:
 ffmpeg -i 16.mp3 -acodec copy -y a.mp3
 ffmpeg -i 17.mp3 -acodec copy -y b.mp3

 and checking again with:
 mp4 a.mp3 b.mp3
 => there is no real gap, but as said above, there's still an audible click

 If you need my source file I could share them in private with you (not
 sure whether the material is copyrighted).

Ticket URL: <https://trac.ffmpeg.org/ticket/9755#comment:2>
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