jpg: add support for YUV421 & YUV442

[ami_stuff]

maybe easy

C:\>ffmpeg -i Test_421.jpg
ffmpeg version N-35892-gc0bea18, Copyright (c) 2000-2011 the FFmpeg developers
  built on Dec 17 2011 13:52:52 with gcc 4.6.2
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-ru
ntime-cpudetect --enable-avisynth --enable-bzlib --enable-frei0r --enable-libope
ncore-amrnb --enable-libopencore-amrwb --enable-libfreetype --enable-libgsm --en
able-libmp3lame --enable-libopenjpeg --enable-librtmp --enable-libschroedinger -
-enable-libspeex --enable-libtheora --enable-libvo-aacenc --enable-libvo-amrwben
c --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --enable-
libxvid --enable-zlib --disable-demuxer=sbg
  libavutil    51. 32. 0 / 51. 32. 0
  libavcodec   53. 46. 0 / 53. 46. 0
  libavformat  53. 26. 0 / 53. 26. 0
  libavdevice  53.  4. 0 / 53.  4. 0
  libavfilter   2. 53. 0 /  2. 53. 0
  libswscale    2.  1. 0 /  2.  1. 0
  libpostproc  51.  2. 0 / 51.  2. 0
[mjpeg @ 02625B60] Unhandled pixel format 0x22211100
[image2 @ 020C2320] Could not find codec parameters (Video: mjpeg, 1023x767 [SAR
 96:96 DAR 1023:767])
Test_421.jpg: could not find codec parameters

C:\>ffmpeg -i Test_442.jpg
ffmpeg version N-35892-gc0bea18, Copyright (c) 2000-2011 the FFmpeg developers
  built on Dec 17 2011 13:52:52 with gcc 4.6.2
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-ru
ntime-cpudetect --enable-avisynth --enable-bzlib --enable-frei0r --enable-libope
ncore-amrnb --enable-libopencore-amrwb --enable-libfreetype --enable-libgsm --en
able-libmp3lame --enable-libopenjpeg --enable-librtmp --enable-libschroedinger -
-enable-libspeex --enable-libtheora --enable-libvo-aacenc --enable-libvo-amrwben
c --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --enable-
libxvid --enable-zlib --disable-demuxer=sbg
  libavutil    51. 32. 0 / 51. 32. 0
  libavcodec   53. 46. 0 / 53. 46. 0
  libavformat  53. 26. 0 / 53. 26. 0
  libavdevice  53.  4. 0 / 53.  4. 0
  libavfilter   2. 53. 0 /  2. 53. 0
  libswscale    2.  1. 0 /  2.  1. 0
  libpostproc  51.  2. 0 / 51.  2. 0
[mjpeg @ 02625B60] Unhandled pixel format 0x12121100
[image2 @ 020C2320] Could not find codec parameters (Video: mjpeg, 1023x767 [SAR
 96:96 DAR 1023:767])
Test_442.jpg: could not find codec parameters

[Carl Eugen Hoyos]

Is there also a "441" format?

[ami_stuff]

no, only these two (+ CMYK & YCbCrK which are not supported by FFmpeg).

[Carl Eugen Hoyos]

Should be fixed by "upscaling" the image to a supported colourspace.

[ami_stuff]

@cehoyos

If you want me to upload not supported supsamples then just tell.

[Carl Eugen Hoyos]

If any of the samples attached here are not decoded correctly, please reopen.
If you have other samples that FFmpeg cannot decode, please open a new ticket (and attach the unsupported samples).