> -----Original Message----- > From: ffmpeg-devel-boun...@ffmpeg.org [mailto:ffmpeg-devel- > boun...@ffmpeg.org] On Behalf Of wm4 > Sent: Friday, February 06, 2015 4:58 PM > To: ffmpeg-devel@ffmpeg.org > Subject: Re: [FFmpeg-devel] [PATCH 1/3] Add clew.c & clew.h to libavutil > > On Fri, 6 Feb 2015 11:06:28 +0000 > "Gupta, Maneesh" <maneesh.gu...@amd.com> wrote: > > > > > > > > -----Original Message----- > > > From: ffmpeg-devel-boun...@ffmpeg.org [mailto:ffmpeg-devel- > > > boun...@ffmpeg.org] On Behalf Of wm4 > > > Sent: Friday, February 06, 2015 4:31 PM > > > To: ffmpeg-devel@ffmpeg.org > > > Subject: Re: [FFmpeg-devel] [PATCH 1/3] Add clew.c & clew.h to > > > libavutil > > > > > > On Fri, 6 Feb 2015 11:14:21 +0100 > > > Hendrik Leppkes <h.lepp...@gmail.com> wrote: > > > > > > > On Fri, Feb 6, 2015 at 11:09 AM, Gupta, Maneesh > > > <maneesh.gu...@amd.com> wrote: > > > > > Hi All, > > > > > > > > > > There are several issues with the way ffmpeg compilation works > > > > > when > > > OpenCL is enabled using --enable-opencl. Chief among them are: > > > > > 1. One needs to also use --extra-cflags, --extra-ldflags & > > > > > -extra-libs to > > > specify the path to the OpenCL header and library files. Otherwise > > > configure fails. > > > > > 2. ffmpeg currently requires OpenCL 1.2, but the build system > > > > > may have > > > another version installed (such as the newer OpenCL 2.0 which has > > > deprecated some 1.2 APIs). > > > > > > > > > > There are a couple of ways to address this. > > > > > > > > > > * One way is the x264 approach which is to bundle cl.h, > > > > > cl_platform.h and > > > a wrapper c file which relies on dynamically loading OpenCL rather > > > than using static linking. This requires modifications to the entire > > > OpenCL based code since we cannot use the OpenCL APIs directly. > > > > > * Another approach taken by LibreOffice and Blender for example > > > > > is to > > > use clew (i.e. The OpenCL Extension Wrangler Library). This has the > > > advantage of letting us use the OpenCL APIs directly yet at the same > > > time relying on dynamically loading OpenCL. The clew project is > > > hosted at https://github.com/OpenCLWrangler/clew. This is maintained > > > by two people (Sergey and Martijn). > > > > > Usage of clew in Libreoffice can be seen @ > > > http://cgit.freedesktop.org/libreoffice/core/tree/clew/source and in > > > Blender @ > > > https://git.blender.org/gitweb/gitweb.cgi/blender.git/tree/HEAD:/ext > > > ern/cl > > > ew. > > > > > > > > > > This patch is for adding clew to the ffmpeg tree. The subsequent > > > > > patches > > > switch the OpenCL code in ffmpeg from using cl.h to using clew. > > > > > > > > > > > > > > > > > Using such a library is fine, if its deemed the best solution > > > > available, but flat-out importing its code into avutil is not. > > > > > > +1 > > > > > > Also look at all these awful "portability" hacks in the added code. > > > It's not a good idea to agree to maintaining this terrible mess. > > > > Alright. Can you suggest an alternate way of building ffmpeg using clew? > Clew has lot of advantages and essentially consists of a single source and > header file. I will modify and resubmit the patch accordingly. > > Convince upstream to package it as real library.
Clew can already be built as a static library. It ships with a cmake file. However I am a little confused here. My intention for using clew was to remove the pain of having to specify multiple parameters to enable the OpenCL feature. If clew is used as a library, instead of having use --extra-cflags, --extra-ldflags to specific the path to standard OpenCL bits I would have to still use them to point ffmpeg to the path to clew. Or am I missing something here? > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
