Fix a bug in the conversion of rgba32->yuv420p. This resulted in garbage images when this conversion was used. I suspect that the same bug may be lurking in other conversions. [The assumption was that the linesize was equal to the width for both the source and destination images. This turns out not to be true in some cases.]
Fix a bug in the conversion of rgba32->yuv420p. This resulted in garbage images
when this conversion was used. I suspect that the same bug may be lurking in
other conversions. [The assumption was that the linesize was equal to the width
for both the source and destination images. This turns out not to be true
in some cases.]


git-svn-id: a4d7c1866f8397a4106e0b57fc4fbf792bbdaaaf@1556 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg