[FFmpeg-devel] [PATCH] Huffyuv: Align the image data in adaptive Huffman tables mode

[Michael Kaufmann]

This patch is for the "adaptive Huffman tables" mode of Huffyuv. In this 
mode, three per-frame huffman tables are saved, and then the actual 
image data. This patch aligns the image data by enlarging one of the 
three Huffman tables by up to 3 bytes.

If the the image data is not aligned, then the bitstream is not saved in 
little endian (like the bitstream of the original Huffyuv codec), but in 
a strange mixture. Decoding the frame is much easier for other decoders 
if the image data is aligned, and it is also possible with better 
performance.

A detailed explanation of the alignment problems can be found in the 3rd 
comment of this blog entry:
http://www.virtualdub.org/blog/pivot/entry.php?id=203

This patch enlarges the Huffman tables in a backwards-compatible way to 
align the image data. Video files generated with this patch can be read 
with older ffmeg versions without any problems. They can also be read by 
the built-in Huffyuv decoder of VirtualDub.

I hope you find this patch useful.

Regards,
Michael
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