[FFmpeg-devel] [PATCH 1/3] lavf/riffenc: Improve spec compliance

Mats Peterson matsp888 at yahoo.com
Fri Mar 11 13:16:27 CET 2016

On 03/11/2016 01:14 PM, Michael Niedermayer wrote:
> On Fri, Mar 11, 2016 at 05:17:18AM +0100, Mats Peterson wrote:
>> On 03/11/2016 05:10 AM, Mats Peterson wrote:
>>> Forget patch 2/3 and 3/3 from the old patch set.
>>>  From the Microsoft documentation for BITMAPINFOHEADER at
>>> https://msdn.microsoft.com/en-us/library/windows/desktop/dd318229%28v=vs.85%29.aspx:
>>> "biSize: Specifies the number of bytes required by the structure. This
>>> value does not include the size of the color table or the size of the
>>> color masks, if they are appended to the end of structure."
>>> So, biSize is always 40. Also, Windows Media Player won't detect video
>>> encoded with Microsoft Video 1 in 8 bpp mode if this value is anything
>>> else than 40. I don't know about other codecs, they probably work.
>>> Anyway, we should stick with the specs, and not include the palette size
>>> in that field.
>>> Regarding the biClrUsed field, I'm setting it to 1 <<
>>> bits_per_coded_sample if palettized video, since setting it to 0 is
>>> another case where it won't work with Windows Media Player and Microsoft
>>> Video 1 in 8 bpp mode.
>>> Mats
>> Once, again, HuffYUV has its own variant of BITMAPINFOHEADER that
>> *does* include the size of the Huffman tables in biSize. That's the
>> only exception as far as I know.
> is huffyuv really the exception ? and not raw rgb or palettes ?
> asv1 and asv2 do not have 40 there
> which codec with a non-palette global header puts 40 there ?

Don't know what you mean by "asv1 and asv2 do not have 40 there". 
Anyway, HuffYUV is the only codec I know of that has a specially 
designed BITMAPINFOHEADER that includes the Huffman tables in it. Hence, 
the larger value for biSize.


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