From 5c963436f67cc2fe6eae93f0fbda588e902f2da4 Mon Sep 17 00:00:00 2001 From: Maneesh Gupta Date: Tue, 27 Jan 2015 15:09:41 +0530 Subject: [PATCH] documentation for -opencl_bench --- doc/fftools-common-opts.texi | 31 +++++++++++++++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-) diff --git a/doc/fftools-common-opts.texi b/doc/fftools-common-opts.texi index 7d52c1a..876c53c 100644 --- a/doc/fftools-common-opts.texi +++ b/doc/fftools-common-opts.texi @@ -294,8 +294,35 @@ Possible flags for this option are: @end table @item -opencl_bench -Benchmark all available OpenCL devices and show the results. This option -is only available when FFmpeg has been compiled with @code{--enable-opencl}. +This option is used to benchmark all available OpenCL devices and print the +results. This option is only available when FFmpeg has been compiled with +@code{--enable-opencl}. + +When FFmpeg is configured with @code{--enable-opencl}, the options for the +global OpenCL context are set via @code{-opencl_options}. See the +``OpenCL Options`` section in the ffmpeg-utils manual for the complete list of +supported options. Amongst others, these options include the ability to select +a specific platform and device to run the OpenCL code on. By default, FFmpeg +will run on the first device of the first platform. While the options for the +global OpenCL context provide flexibility to the user in selecting the OpenCL +device of their choice, most users would probably want to select the fastest +OpenCL device for their system. + +This option assists the selection of the most efficient configuration by +identifying the appropriate device for the user’s system. The built-in +benchmark is run on all the OpenCL devices and the performance is measured for +each device. The devices in the results list are sorted based on their +performance with the fastest device listed first. The user can subsequently +invoke Ffmpeg using the device deemed most appropriate via +@code{--opencl_options} to obtain the best performance for the OpenCL +accelerated code. + +Typical usage to use the fastest OpenCL device involve the following steps: +@example +ffmpeg -opencl_bench +Note down the platform ID (@var{pIDx}) & device ID (@var{dIDx}) of the first i.e. fastest device in the list. +ffmpeg -opencl_options platform_idx=@var{pIDx}:device_idx=@var{dIDx} ... +@end example @item -opencl_options options (@emph{global}) Set OpenCL environment options. This option is only available when -- 1.9.5.msysgit.0