FFmpeg can't handle h264 NAL units that are split between packets

[Rokolell]

When a NAL unit is split between AVPackets, FFmpeg fails to decode it properly, causing graphical glitching.

How to reproduce:

• Download the provided archive with example data.
• Compile test.c with

  gcc -lavcodec -lavutil -g test.c -o test
  

• Run the test with

  ./test .
  

• View 420-440.yuv420p in your preferred raw image viewer to see the glitches. The resolution for each frame is shown by the example program.

Example:

Example result created by the Windows Media Foundation Decoder (which can handle these packets perfectly fine):

[Rokolell]

I preemptively uploaded the example to the videolan fileshare.

[mkver]

Our decoders work on proper packets (for the H.264 decoder this means "access units", but generally proper NALUs (that don't span multiple packets) if the AV_CODEC_FLAG2_CHUNKS is set). If you don't have proper packets, use the parsing API to assemble them.

[Balling]

So why does MFF has no problem