[FFmpeg-trac] #1726(undetermined:closed): Mono TrueHD file fails to decode

FFmpeg trac at avcodec.org
Fri Sep 3 02:47:11 EEST 2021

#1726: Mono TrueHD file fails to decode
             Reporter:  Carl Eugen   |                    Owner:  (none)
  Hoyos                              |
                 Type:  defect       |                   Status:  closed
             Priority:  important    |                Component:
                                     |  undetermined
              Version:  git-master   |               Resolution:  fixed
             Keywords:  thd          |               Blocked By:
  regression mlp                     |
             Blocking:               |  Reproduced by developer:  1
Analyzed by developer:  0            |
Comment (by Balling):

 Interesting, so even now with 16 samples present, the reencoded file is
 larger (13866334 bytes vs 11141326 bytes) but also no longer has flags to
 drop the second channel and does not print with -v debug "Mono stream with
 2 substreams, ignoring 2nd".

 P.S. It is not printing stereo, but it creates wrong wav with 2 channels
 with second channel zeroed out in both source and reencoded file (when
 ffmpeg recognized the file as mono, the result was the same, two channel
 in wav).

 P.S.2 WHAT IS VERY IMPORTANT is that LG C9 which uses hardware decoder for
 Truehd and Truehd + Atmos (yep, it decodes Atmos packed in MAT 2.0 by
 Lavfilters even on the internal speackers and signals Atmos) thinks that
 the reencoded truehd file is not longer mono: when you select Right+Right
 in the LG C9 sound menu it plays nothing on reencoded file (because
 reencoded file has nothing in the right channel and is not tagged as mono)
 while on source file Right+Right is the same as L+R and L+L, since mono is
 being played on all speakers. What is also a problem is that reencoded
 file is so much less loud and also that it loses sound when you select
 only one speacker (R+R is no sound as I said but left+left is less loud
 again). That may be a difference between stereo and mono or DRC (Dynamic
 range compression) that is not supported in mlpenc (while eac3 and ac3 do
 support it).
Ticket URL: <https://trac.ffmpeg.org/ticket/1726#comment:5>
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