[Libav-user] Inplace YUV to RGBA conversion

Prunk Dump prunkdump at gmail.com
Sun May 15 11:43:48 CEST 2011

Hi !

 I'am writing a program that needs a RBGA video format to send data to an
opengl alpha masked texture. Thus, for convenience, I decided to encode my
video frames in two files.

 -The fist contain RGB data with maked pixel always the same color. Thus
converting frames with a MPEG4 video codec give good file size and doesn't
waste data to encode useless pixels.

 -The second contain Alpha data encoded into my own codec and file format.

 I try to use libavcodec to decode as fast as possible the first file to
send RGB data to my RGBA texture buffer. But swscale don't give me an
accelered YUV to RGBA colorspace conversion, so décoding frames is too slow
for me.

 So rather than converting the entire YUV frame, I would like to convert
only the updated pixels given by the P frames. Does swsccale or libavcodec
have a particular optimization for this sort of inplace decoding ? (the
swscale destination buffer is not changed so it can be updated only by
applying diff)

 Moreover, in my case the number of updated pixels is often very low !
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