[FFmpeg-devel] Patch review request: 10bit DNxHD decoding support

[Maxim]

Joseph Artsimovich schrieb:
> Hi,
>
> At this point I am happy with my patch adding support for decoding 10bit DNxHD, apart from poor performance due to the lack of assembly optimized IDCT code that can handle 10bit samples.  Please review and give feedback.
>   

I'm currently working on a support for the 10bit IDCT (both SSE2 and
Altivec). Some minor modifications (regarding rounding constants) of the
existing functions (idct_altivec.c and idct_sse2_xvid.c) are required.
There are two minor issues:

* it will be difficult to obtain the same transform precision using the
functions mentioned above because of the higher data pass. A proprietary
10bit video codec I'm currently working on produces 14bits DCT
coefficients instead of 12bits for the 8bit IDCT. I think this is a
minor issue because all codes currently supporting 10bits are I-Frames
only and doesn't rely on very exact IDCT.

* the SSE2 engine is slow as hell on early Intel CPUs like mine (Intel
Core Duo "Yonah") so a good-performance MMX2 version will be appreciated too

Best regards
Maxim Poliakovski