[FFmpeg-trac] #7291(ffmpeg:new): 24bit flac converted to alac, bit-depth atom in output file incorrectly set at 16bit

FFmpeg trac at avcodec.org
Sun Jul 1 14:17:00 EEST 2018


#7291: 24bit flac converted to alac, bit-depth atom in output file incorrectly set
at 16bit
-----------------------------------+---------------------------------------
             Reporter:  pssturges  |                     Type:  defect
               Status:  new        |                 Priority:  normal
            Component:  ffmpeg     |                  Version:  unspecified
             Keywords:             |               Blocked By:
             Blocking:             |  Reproduced by developer:  0
Analyzed by developer:  0          |
-----------------------------------+---------------------------------------
 Summary of the bug: 24bit flac converted to alac, bit-depth atom in output
 file incorrectly set at 16bit not 24bit
 How to reproduce:
 {{{
 % ffmpeg -i 24bitflac.flac -y -map 0:0 -c:a:0 alac 24bitalac.m4a
 ffmpeg version 2.8.14-0ubuntu0.16.04.1
 mp4file --dump 24bitalac.m4a | grep sample
         "24bitalac.m4a": sampleSize = 16 (0x0010)
        "24bitalac.m4a": sampleSize = 0 (0x00000000)
        "24bitalac.m4a": sampleCount = 6096 (0x000017d0)
 }}}
 This causes the resultant file to play as white noise in some players as
 they attempt to play it as 16bit file. Logitech Media Server is one such
 player.

 An extensive investigation of this issue can be found on the slim devices
 forum found here:
 https://forums.slimdevices.com/showthread.php?102059-24-bit-ALAC-files-
 being-truncated-to-16-bit

 Forum member 'bpa' has suggested a patch in that thread which I have
 tested and found to correct the problem

--
Ticket URL: <https://trac.ffmpeg.org/ticket/7291>
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