indeo4 artefacts with scalability and low quality

[ami_stuff]

ffmpeg.exe -i QT-IV44.mov -vcodec msmpeg4v2 -an out.avi
ffmpeg version 0.9.0.git-0af34c4, Copyright (c) 2000-2012 the FFmpeg developers
  built on Jan  2 2012 19:27:43 with gcc 4.5.2
  configuration: --disable-ffplay --disable-ffserver --disable-asm --disable-yas
m --disable-shared --enable-static
  libavutil      51. 33.100 / 51. 33.100
  libavcodec     53. 50.100 / 53. 50.100
  libavformat    53. 29.100 / 53. 29.100
  libavdevice    53.  4.100 / 53.  4.100
  libavfilter     2. 57.101 /  2. 57.101
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0.  5.100 /  0.  5.100

Seems stream 1 codec frame rate differs from container frame rate: 1000000.00 (1
000000/1) -> 24.00 (1000000/41667)
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'QT-IV44.mov':
  Metadata:
    creation_time   : 2002-10-02 22:35:06
  Duration: 00:00:05.95, start: 0.000000, bitrate: 524 kb/s
    Stream #0:0(eng): Audio: adpcm_ima_qt (ima4 / 0x34616D69), 11025 Hz, 2 chann
els, s16, 88 kb/s
    Metadata:
      creation_time   : 2002-10-02 22:35:06
      handler_name    : ?Apple Alias Data Handler
    Stream #0:1(eng): Video: indeo4 (IV41 / 0x31345649), yuv410p, 192x128, 427 k
b/s, 24 fps, 24 tbr, 1000k tbn, 1000k tbc
    Metadata:
      creation_time   : 2002-10-02 22:35:06
      handler_name    : ?Apple Alias Data Handler
Incompatible pixel format 'yuv410p' for codec 'msmpeg4v2', auto-selecting format
 'yuv420p'
[buffer @ 016c28f0] w:192 h:128 pixfmt:yuv410p tb:1/1000000 sar:0/1 sws_param:
[buffersink @ 016c2ab0] auto-inserting filter 'auto-inserted scale 0' between th
e filter 'src' and the filter 'out'
[scale @ 016c2cc0] w:192 h:128 fmt:yuv410p -> w:192 h:128 fmt:yuv420p flags:0x4
Output #0, avi, to 'out.avi':
  Metadata:
    creation_time   : 2002-10-02 22:35:06
    ISFT            : Lavf53.29.100
    Stream #0:0(eng): Video: msmpeg4v2 (MP42 / 0x3234504D), yuv420p, 192x128, q=
2-31, 200 kb/s, 24 tbn, 24 tbc
    Metadata:
      creation_time   : 2002-10-02 22:35:06
      handler_name    : ?Apple Alias Data Handler
Stream mapping:
  Stream #0:1 -> #0:0 (indeo4 -> msmpeg4v2)
Press [q] to stop, [?] for help
[msmpeg4v2 @ 016b7500] warning, clipping 1 dct coefficients to -127..127
frame=  123 fps=  0 q=11.4 size=     210kB time=00:00:05.12 bitrate= 336.1kbits/
frame=  143 fps=  0 q=9.1 Lsize=     245kB time=00:00:05.95 bitrate= 336.4kbits/
s
video:236kB audio:0kB global headers:0kB muxing overhead 3.809374%

[cehoyos]

Possibly unrelated to ticket #845.

[ami_stuff]

Finally I was able to reproduce this with new samples.

The problem is that FFmpeg's indeo4 decoder doesn't work correctly when file is encoded with enabled "Scalability" and encoding quality is lower than 35% (see attached samples, esp. "scal_[20/25/30]p_every_1.avi").