mjpeg enc: sampling factors too large for interleaved scan

[ami_stuff]

the output jpg file does not decode with ImageMagick/IrfanView and other software because of
"sampling factors too large for interleaved scan" error

​http://nl.nrk.no/podkast/aps/10908/nrk_radioresepsjonen_2012-1129-0325_6348979963.mp3

C:\>ffmpeg -probesize 9000000 -i nrk_radioresepsjonen_2012-1129-0325_6348979
963.mp3 out.jpg
ffmpeg version N-47325-gb90e795 Copyright (c) 2000-2012 the FFmpeg developers
  built on Dec  1 2012 02:23:25 with gcc 4.5.0 (GCC) 20100414 (Fedora MinGW 4.5.
0-1.fc14)
  configuration: --prefix=/var/www/users/research/ffmpeg/snapshots/build --arch=
x86 --target-os=mingw32 --cross-prefix=i686-pc-mingw32- --cc='ccache i686-pc-min
gw32-gcc' --enable-w32threads --enable-memalign-hack --enable-runtime-cpudetect
--enable-cross-compile --enable-static --disable-shared --extra-libs='-lws2_32 -
lwinmm -lpthread' --extra-cflags='--static -I/var/www/users/research/ffmpeg/snap
shots/build/include' --extra-ldflags='-static -L/var/www/users/research/ffmpeg/s
napshots/build/lib' --enable-bzlib --enable-zlib --enable-gpl --enable-version3
--enable-nonfree --enable-libx264 --enable-libspeex --enable-libtheora --enable-
libvorbis --enable-libfaac --enable-libxvid --enable-libopencore-amrnb --enable-
libopencore-amrwb --enable-libmp3lame --enable-libvpx --disable-decoder=libvpx
  libavutil      52. 10.100 / 52. 10.100
  libavcodec     54. 78.100 / 54. 78.100
  libavformat    54. 41.100 / 54. 41.100
  libavdevice    54.  3.101 / 54.  3.101
  libavfilter     3. 23.104 /  3. 23.104
  libswscale      2.  1.103 /  2.  1.103
  libswresample   0. 17.101 /  0. 17.101
  libpostproc    52.  2.100 / 52.  2.100
[mp3 @ 0x1eebf40] Format mp3 detected only with low score of 24, misdetection po
ssible!
[mp3 @ 0x1eebf40] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x1eebf40] Estimating duration from bitrate, this may be inaccurate
Input #0, mp3, from 'nrk_radioresepsjonen_2012-1129-0325_6348979963.mp3':
  Metadata:
    title           : 29.11.2012 Radioresepsjonen
    album           : NRK P3 - Radioresepsjonen
    artist          : NRK P3 - Radioresepsjonen
    genre           : Podcast
    date            : 2012
  Duration: 01:20:31.24, start: 0.000000, bitrate: 127 kb/s
    Stream #0:0: Audio: mp3, 44100 Hz, stereo, s16p, 128 kb/s
    Stream #0:1: Video: bmp, bgr24, 1200x1200, 90k tbr, 90k tbn, 90k tbc
    Metadata:
      title           :
      comment         : Cover (front)
    Stream #0:2: Video: bmp, bgr24, 1200x1200, 90k tbr, 90k tbn, 90k tbc
    Metadata:
      title           :
      comment         : Cover (front)
[image2 @ 0x1ee3940] Frame rate very high for a muxer not efficiently supporting
 it.
Please consider specifying a lower framerate, a different muxer or -vsync 2
Output #0, image2, to 'out.jpg':
  Metadata:
    title           : 29.11.2012 Radioresepsjonen
    album           : NRK P3 - Radioresepsjonen
    artist          : NRK P3 - Radioresepsjonen
    genre           : Podcast
    date            : 2012
    encoder         : Lavf54.41.100
    Stream #0:0: Video: mjpeg, yuvj444p, 1200x1200, q=2-31, 200 kb/s, 90k tbn, 9
0k tbc
    Metadata:
      title           :
      comment         : Cover (front)
Stream mapping:
  Stream #0:1 -> #0:0 (bmp -> mjpeg)
Press [q] to stop, [?] for help
frame=    1 fps=0.0 q=8.5 Lsize=       0kB time=00:00:00.00 bitrate=   0.0kbits/
s
video:125kB audio:0kB subtitle:0 global headers:0kB muxing overhead -100.000000%

[Carl Eugen Hoyos]

If there is an issue in FFmpeg (I don't know), it is reproducible with:
$ ffmpeg -i tests/lena.pnm out.jpg
"Regression" since 9f02d4e

Work-around is to specify a colour-space != yuvj444p