[FFmpeg-devel] [PATCH] mpeg2dec: fix decoding field pictures

[Nekopanda]

> On Fri, Feb 09, 2018 at 02:03:24AM +0900, Nekopanda wrote:

>>  - Fix field selection for skipped macroblocks
>> 
>>  For B field pictures, the spec says,
>> 
>>  > The prediction shall be made from the field of the same parity as the 
> field being predicted.
>> 
>>  I did it.
>> 
>>  - Fix motion vector rounding for chroma components
>> 
>>  In 16x8 motion compensation, for lower 16x8 region, the input to 
> mpeg_motion() for motion_y was "motion_y + 16", which causes wrong 
> rounding. For 4:2:0, chroma scaling for y is dividing by two and rounding toward 
> zero. When motion_y < 0 and motion_y + 16 > 0, the rounding direction of 
> "motion_y" and "motion_y + 16" is different and rounding 
> "motion_y + 16" would be incorrect.
>> 
>>  We should input "motion_y" as is to round correctly. I add 
> "is_16x8" flag to do that.
> 
> please split this patch in 2.
> I think these are 2 independant bugfixes.
> 
> also please update the fate checksums so make fate does not break after
> either patch


I split into 2 patches and sent them. They also include new checksums.