[FFmpeg-trac] #4085(swresample:new): Support PLII upmixing

[FFmpeg]

#4085: Support PLII upmixing
-------------------------------------+-------------------------------------
               Reporter:  cehoyos    |                  Owner:
                   Type:             |                 Status:  new
  enhancement                        |              Component:  swresample
               Priority:  wish       |               Keywords:
                Version:  git-       |               Blocking:
  master                             |  Analyzed by developer:  0
             Blocked By:             |
Reproduced by developer:  0          |
-------------------------------------+-------------------------------------
 http://thread.gmane.org/gmane.comp.video.ffmpeg.user/54545

 FFmpeg does support PLII down-mixing (see tickets #709 and #3455) but does
 not support upmixing afaict. I will attach a sample from the MythTV
 collection that plays surround sound on my receiver, upmixing to six
 channels does not produce a similar result.
 {{{
 $ ffmpeg -i channelsPLII.mpg -ac 6 out.wav
 ffmpeg version N-67396-g90cdec5 Copyright (c) 2000-2014 the FFmpeg
 developers
   built on Nov  6 2014 00:16:59 with gcc 4.7 (SUSE Linux)
   configuration: --enable-gpl
   libavutil      54. 11.100 / 54. 11.100
   libavcodec     56. 10.102 / 56. 10.102
   libavformat    56. 12.101 / 56. 12.101
   libavdevice    56.  2.100 / 56.  2.100
   libavfilter     5.  2.103 /  5.  2.103
   libswscale      3.  1.101 /  3.  1.101
   libswresample   1.  1.100 /  1.  1.100
   libpostproc    53.  3.100 / 53.  3.100
 Input #0, mpeg, from 'channelsPLII.mpg':
   Duration: 00:00:31.82, start: 0.740000, bitrate: 462 kb/s
     Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p(tv), 480x576
 [SAR 8:5 DAR 4:3], max. 2420 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
     Stream #0:1[0x1c0]: Audio: mp2, 48000 Hz, stereo, s16p, 224 kb/s
 Output #0, wav, to 'out.wav':
   Metadata:
     ISFT            : Lavf56.12.101
     Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 48000 Hz, 5.1,
 s16, 4608 kb/s
     Metadata:
       encoder         : Lavc56.10.102 pcm_s16le
 Stream mapping:
   Stream #0:1 -> #0:0 (mp2 (native) -> pcm_s16le (native))
 Press [q] to stop, [?] for help
 size=   17915kB time=00:00:31.84 bitrate=4608.0kbits/s
 video:0kB audio:17914kB subtitle:0kB other streams:0kB global headers:0kB
 muxing overhead: 0.000556%
 }}}
 MythTV contains a PLII decoder that supports upmixing under GPL.

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Ticket URL: <https://trac.ffmpeg.org/ticket/4085>
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