bad output when encoding mjpeg to libx264

[Waraqa]

Summary of the bug:
I'm trying to encode AVI (MJPEG) video to MP4 (H.264) but the output video is damaged (grey color instead of the video).
Although I see no errors while encoding, There are many errors while playing the output. (I'm using old ffplay to play the output)

% ffplay out.mp4 
ffplay version 0.8.12, Copyright (c) 2003-2011 the FFmpeg developers
  built on Jun 13 2012 09:57:57 with gcc 4.6.3 20120306 (Red Hat 4.6.3-2)
  configuration: --prefix=/usr --bindir=/usr/bin --datadir=/usr/share/ffmpeg --incdir=/usr/include/ffmpeg --libdir=/usr/lib --mandir=/usr/share/man --arch=i686 --extra-cflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i686 -mtune=atom -fasynchronous-unwind-tables' --enable-bzlib --enable-libcelt --enable-libdc1394 --enable-libdirac --enable-libfreetype --enable-libgsm --enable-libmp3lame --enable-libopenjpeg --enable-librtmp --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-x11grab --enable-avfilter --enable-postproc --enable-pthreads --disable-static --enable-shared --enable-gpl --disable-debug --disable-stripping --shlibdir=/usr/lib --cpu=i686 --enable-runtime-cpudetect
  libavutil    51.  9. 1 / 51.  9. 1
  libavcodec   53.  8. 0 / 53.  8. 0
  libavformat  53.  5. 0 / 53.  5. 0
  libavdevice  53.  1. 1 / 53.  1. 1
  libavfilter   2. 23. 0 /  2. 23. 0
  libswscale    2.  0. 0 /  2.  0. 0
  libpostproc  51.  2. 0 / 51.  2. 0
[h264 @ 0xb24006e0] top block unavailable for requested intra4x4 mode -1 at 1 0
[h264 @ 0xb24006e0] error while decoding MB 1 0, bytestream (4794)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'out.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf55.34.101
  Duration: 00:00:00.97, start: 0.036281, bitrate: 1275 kb/s
    Stream #0.0(und): Video: h264 (High 4:2:2), yuvj420p, 640x480, 1180 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc
    Stream #0.1(und): Audio: aac, 44100 Hz, mono, s16, 127 kb/s
[buffersink @ 0xb5100960] auto-inserting filter 'auto-inserted scaler 0' between the filter 'src' and the filter 'out'
[scale @ 0xb5100d60] w:640 h:480 fmt:yuvj420p -> w:640 h:480 fmt:yuv420p flags:0x4
[h264 @ 0xb24006e0] top block unavailable for requested intra4x4 mode -1 at 1 0
[h264 @ 0xb24006e0] error while decoding MB 1 0, bytestream (4794)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
[h264 @ 0xb24006e0] top block unavailable for requested intra4x4 mode -1 at 13 0
[h264 @ 0xb24006e0] error while decoding MB 13 0, bytestream (12130)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
[h264 @ 0xb24006e0] Reference 4 >= 3
[h264 @ 0xb24006e0] error while decoding MB 25 3, bytestream (46)
[h264 @ 0xb24006e0] concealing 1104 DC, 1104 AC, 1104 MV errors
[h264 @ 0xb24006e0] Reference 4 >= 4 vq=  118KB sq=    0B f=0/0   f=0/0   
[h264 @ 0xb24006e0] error while decoding MB 1 0, bytestream (4764)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors   
[h264 @ 0xb24006e0] top block unavailable for requested intra mode at 27 0
[h264 @ 0xb24006e0] error while decoding MB 27 0, bytestream (4852)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
[h264 @ 0xb24006e0] top block unavailable for requested intra4x4 mode -1 at 6 0
[h264 @ 0xb24006e0] error while decoding MB 6 0, bytestream (5015)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
[h264 @ 0xb24006e0] Reference 4 >= 4
[h264 @ 0xb24006e0] error while decoding MB 25 2, bytestream (3801)
[h264 @ 0xb24006e0] concealing 1144 DC, 1144 AC, 1144 MV errors
[h264 @ 0xb24006e0] concealing 1190 DC, 1190 AC, 1190 MV errors   
[h264 @ 0xb24006e0] top block unavailable for requested intra4x4 mode -1 at 1 0
[h264 @ 0xb24006e0] error while decoding MB 1 0, bytestream (9499)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
[h264 @ 0xb24006e0] top block unavailable for requested intra4x4 mode -1 at 14 0
[h264 @ 0xb24006e0] error while decoding MB 14 0, bytestream (4488)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
[h264 @ 0xb24006e0] Reference 4 >= 4 vq=   81KB sq=    0B f=0/0   
[h264 @ 0xb24006e0] error while decoding MB 4 0, bytestream (4670)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
[h264 @ 0xb24006e0] top block unavailable for requested intra4x4 mode -1 at 19 0
[h264 @ 0xb24006e0] error while decoding MB 19 0, bytestream (4876)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
[h264 @ 0xb24006e0] concealing 1110 DC, 1110 AC, 1110 MV errors   
[h264 @ 0xb24006e0] top block unavailable for requested intra mode at 1 0
[h264 @ 0xb24006e0] error while decoding MB 1 0, bytestream (6064)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
[h264 @ 0xb24006e0] Reference 4 >= 4 vq=   60KB sq=    0B f=0/0   
[h264 @ 0xb24006e0] error while decoding MB 1 0, bytestream (6915)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
[h264 @ 0xb24006e0] Reference 4 >= 4
[h264 @ 0xb24006e0] error while decoding MB 11 0, bytestream (6536)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
[h264 @ 0xb24006e0] concealing 1198 DC, 1198 AC, 1198 MV errors   
[h264 @ 0xb24006e0] top block unavailable for requested intra4x4 mode -1 at 2 0
[h264 @ 0xb24006e0] error while decoding MB 2 0, bytestream (5228)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
[h264 @ 0xb24006e0] Reference 4 >= 4 vq=   29KB sq=    0B f=0/0   
[h264 @ 0xb24006e0] error while decoding MB 26 0, bytestream (5218)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
[h264 @ 0xb24006e0] Reference 4 >= 4
[h264 @ 0xb24006e0] error while decoding MB 4 0, bytestream (5934)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
[h264 @ 0xb24006e0] Reference 4 >= 4
[h264 @ 0xb24006e0] error while decoding MB 12 0, bytestream (5543)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
[h264 @ 0xb24006e0] top block unavailable for requested intra4x4 mode -1 at 1 0
[h264 @ 0xb24006e0] error while decoding MB 1 0, bytestream (7420)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
[h264 @ 0xb24006e0] Reference 4 >= 4
[h264 @ 0xb24006e0] error while decoding MB 19 0, bytestream (3297)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
[h264 @ 0xb24006e0] concealing 1197 DC, 1197 AC, 1197 MV errors   
[h264 @ 0xb24006e0] top block unavailable for requested intra4x4 mode -1 at 8 0
[h264 @ 0xb24006e0] error while decoding MB 8 0, bytestream (3387)
[h264 @ 0xb24006e0] concealing 1200 DC, 1200 AC, 1200 MV errors
   0.94 A-V: -2.298 s:1.2 aq=    0KB vq=    0KB sq=    0B f=0/0

How to reproduce:
I have copied a sample (using -c:v copy) and uploaded it, so that developers can reproduce the bug.

1. download the sample.
2. encode it using

   % ffmpeg -i input.avi -c:v libx264 out.mp4
   

3. play it.

[Waraqa]

sample input

[Carl Eugen Hoyos]

You need at least FFmpeg 0.9 to play the output file.

For future tickets: Please always test current FFmpeg git head before reporting problems, features (like H.264 4:2:2 decoding) are not backported to old releases.