On 11/04/17 12:26, Mark Thompson wrote: > On 11/04/17 08:30, Jun Zhao wrote: >> From 9bab458006369f427fa2f4c6248ee89329e81067 Mon Sep 17 00:00:00 2001 >> From: Jun Zhao <jun.z...@intel.com> >> Date: Tue, 11 Apr 2017 14:37:07 +0800 >> Subject: [PATCH] hwcontext_vaapi: use the special UC copy for downloading >> frames. >> >> used SSE4 UC function for copying image data from GPU mapped memory, >> see >> https://software.intel.com/en-us/articles/copying-accelerated-video-decode-frame-buffers >> >> before this change, VA-API HWAccel decoder copy image data from GPU >> mapped memory used vaCreateImage/vaGetImage/av_frame_copy, now use >> vaDeriveImage/av_image_copy_uc_from. >> >> decoding a 3000 frames 1080p h264 stream in Intel(R) Core(TM) >> i5-6260U CPU @ 1.80GHz, the CPU usage and decode fps as follow: >> >> 1. Software decoder. >> ./ffmpeg -i ./skyfall2-trailer.mp4 -f null /dev/null >> >> CPU: 80%, fps: 334fps >> >> 2a. vaCreateImage/vaGetImage/av_frame_copy >> ./ffmpeg -hwaccel vaapi -vaapi_device /dev/dri/renderD128 -i >> skyfall2-trailer.mp4 -f null /dev/null >> >> CPU: 12%, fps: 147fps >> >> 2b. vaDeriveImage/av_image_copy_uc_from >> ./ffmpeg -hwaccel vaapi -vaapi_device /dev/dri/renderD128 -i >> skyfall2-trailer.mp4 -f null /dev/null >> >> CPU: 23%, fps: 628fps >> >> Signed-off-by: Jun Zhao <jun.z...@intel.com> >> --- > > This change was considered in libav when the UC copy function was introduced > (<https://lists.libav.org/pipermail/libav-devel/2016-August/078826.html>, > <https://lists.libav.org/pipermail/libav-devel/2016-August/078825.html>), but > was not in the end applied. > > The reasons for this were: > > * It had much worse performance on the low-power cores - try your benchmark > above on Braswell.
Running on a Braswell N3700, input is 38072 frames of 1920x1080 H.264. No download at all: 520fps, 52s CPU Before patch, 4 threads: 107fps, 237s CPU Before patch, 1 thread: 90fps, 233s CPU After patch, 4 threads: 30fps, 1294s CPU After patch, 1 thread: 28fps, 1305s CPU - Mark _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
