[FFmpeg-devel] [PATCH] configure: autodetect opencl

Gupta, Maneesh Maneesh.Gupta at amd.com
Mon Mar 2 11:46:04 CET 2015

> -----Original Message-----
> From: ffmpeg-devel-bounces at ffmpeg.org [mailto:ffmpeg-devel-
> bounces at ffmpeg.org] On Behalf Of wm4
> Sent: Monday, March 02, 2015 2:26 PM
> To: ffmpeg-devel at ffmpeg.org
> Subject: Re: [FFmpeg-devel] [PATCH] configure: autodetect opencl
> On Mon, 2 Mar 2015 07:29:11 +0000
> "Gupta, Maneesh" <Maneesh.Gupta at amd.com> wrote:
> > Hi,
> >
> > Similar to the way SDL is being autodetected, the attached patch proposes
> to autodetect OpenCL.
> SDL shouldn't be autodetected at all, since it's not a system lib, and often
> causes all sorts of problems even if you don't use anything SDL-specific.

 [Gupta, Maneesh] Running grep "autodetect" on configure of ffmpeg gives:
  --disable-dxva2          disable DXVA2 code [autodetect]
  --disable-vaapi          disable VAAPI code [autodetect]
  --disable-vda            disable VDA code [autodetect]
  --disable-vdpau          disable VDPAU code [autodetect]
  --disable-bzlib          disable bzlib [autodetect]
  --disable-iconv          disable iconv [autodetect]
  --disable-lzma           disable lzma [autodetect]
  --disable-opencl         disable OpenCL code [autodetect]
  --disable-sdl            disable sdl [autodetect]
  --disable-xlib           disable xlib [autodetect]
  --disable-zlib           disable zlib [autodetect]

I see a lot of modules that are autodetected. And not all of them are system libs.
I quoted SDL in my original mail only because the OpenCL detection code is done similar to the way SDL is being detected. Otherwise in my opinion OpenCL code is really on the same league as DXVA2 & VAAPI since they attempt to harness additional capabilities of the underlying hardware.

> > Rationale for the change:
> > * OpenCL linking typically happens against the OpenCL ICD's import library.
> Hence there is no hard-linking against the OpenCL ICD's DLL/shared library.
> So ffmpeg should continue to run fine for non-OpenCL cases even when
> OpenCL runtime is not available on the user's system.
> > * Enabling OpenCL is relatively low-impact since it does not automatically
> disable or override any existing functionality. The user still needs to explicitly
> specify opencl=1 in the filter options when using ffmpeg to use the OpenCL
> path.
> >
> > Please review the patch and share your comments on the same.
> >
> > Thanks and Regards,
> > Maneesh
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