On Thu, May 14, 2015 at 2:52 PM, Stefano Sabatini <stefa...@gmail.com> wrote:
> On date Thursday 2015-05-14 13:01:51 +0200, Stefano Sabatini encoded: > > On date Tuesday 2015-05-12 15:54:17 +0200, Hendrik Leppkes encoded: > [...] > > > One limitation is as the manual said, it needs to be copied from the > > > GPU to system memory. ffmpeg_dxva2.c does not implement a optimized > > > copy function for this, it uses plain old memcpy. > > > Intel introduced a new instruction for this in SSE4, MOVNTDQA, which > > > is optimized for copying from USWC memory (Uncacheable Speculative > > > Write Combining) to system memory. Using this may help speed up the > > > process significantly, and VLC probably uses it. > > > > Now the question is, how would be possible to optimize GPU to CPU copy > > to get an overall performance gain? At least VLC seems able to get > > better performances when using HW decoding, but I'm not sure it is > > copying decoded data back to the CPU (indeed it may perform direct > > rendering). > > Self-reply: > commit 62107e563f979c638f9a5f58cdfd5639d9c63ac7 > Author: Laurent Aimar <fen...@videolan.org> > Date: Tue Nov 17 01:09:43 2009 +0100 > > Improved performance when copying video surface in dxva2. > > That is, VLC is using optimized GPU->CPU copy when the relevant SSE2 > instructions are available. > I have a first hackish patch, performed some tests and I got some significant performance gains, on my iCore5 with Intel Graphics HD4000 I have now the same performance as the software decoder using DXVA2 for decoding a H.264 1920x1080 video, but using only a single thread. The patch as is is a hack, since I had to modify the compilation flags to enable assembly compilation in the ffmpeg_dxva2.c file. I should probably create an optimized copy function in libavutil, comments are welcome. The IDirect3D9_CreateDevice(... GetShellWindow ...) -> ..GetDesktopWindow change is required to make it compile under MinGW (with MinGW64 it is probably not required, I still have to switch to MinGW64 but allowing MinGW compilation is still worthwhile).
0001-ffmpeg_dxva.c-add-support-to-optimized-GPU-to-CPU-co.patch
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