[MPlayer-dev-eng] [PATCH] vf_scale: prevent copying data when nothing else to do

[Reimar Döffinger]

On Fri, Aug 17, 2012 at 10:38:14PM +0800, Xidorn Quan wrote:
> It is a simple patch to prevent vf_scale from just copying data when
> nothing need to be scaled actually.

I don't think that's correct, if the frame buffer after the filter is different
than the one before (e.g. because the incoming frame is a reference
frame and thus has a PRESERVE flag while the next filter e.g. is expand
drawing the vo) a copy is still needed.
However that reminds me that it would be really nice if vf_scale and
libswscale could operate in-place, it would reduce the memory bandwidth
required by e.g. 10-bit to 16-bit conversion in about half and solve
this problem as a side effect.
Would be a good bit of effort to implement properly though.