[FFmpeg-trac] #2852(avcodec:new): dcadec internal default downmix is not normalised and reduces stereo separation by cross mixing L* and R*.

[FFmpeg]

#2852: dcadec internal default downmix is not normalised and reduces stereo
separation by cross mixing L* and R*.
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             Reporter:  AndyF       |                    Owner:
                 Type:  defect      |                   Status:  new
             Priority:  normal      |                Component:  avcodec
              Version:  git-master  |               Resolution:
             Keywords:  dca         |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |
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Comment (by AndyF):

 It's fixed WRT the cross mixing.

 It seems that it's now partially normalised - probably enough not to clip
 too bad on real world content that doesn't max all channels equally, but
 it's currently louder than -ac2 or the same content but an ac3 version
 downmixed like : -drc_scale 0 -request_channels 2 .

 This applies to streams that hit the default table and those that have
 metadata - I haven't really had enough time to look properly, I suspect
 for the metadata case post mix gain adjustment should be decoded and
 applied.

 I see commits to do with including LFE, but it doesn't seem to be included
 in the mix currently (not that I would want that to be default) what are
 the plans for this eg, default off and a new option?

 I added some debugging so I can see the metadata if present and do have a
 stream with LFE non zero.

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Ticket URL: <https://trac.ffmpeg.org/ticket/2852#comment:4>
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