[FFmpeg-devel] [RFC] QSV support clarifications

Michael Niedermayer michael at niedermayer.cc
Tue Oct 13 13:14:30 CEST 2015

CC-ing Ivan so he doesnt miss this though he should be following
ffmpeg-devel and keeping an eye on qsv anyway ...

On Mon, Oct 12, 2015 at 08:10:04PM +0200, Stefano Sabatini wrote:
> Hi all,
> I wanted to test QSV encoding and decoding, which is included since
> several months in FFmpeg, and have a few questions.
> 1. QSV encoding and decoding depends on libmfx, but no references are
> present in the code to the library, so I have to suppose that the
> required library is this one:
> https://github.com/lu-zero/mfx_dispatch
> While at it, do you know what's the point of the mfx_dispatch
> component (why adding the intel media library path to flags is not
> enough)?
> 2. The mfx_dispatch library compiles fine on my system, but then I
> wonder how it is supposed to reference the Intel Media library:
> https://software.intel.com/en-us/intel-media-server-studio
> ...
> I'm able to compile FFmpeg with --enable-libmfx after installing
> the mfx_dispatch library, and run this command:
> ffmpeg -i test.mp4 -c:v h264_qsv -y test.out.mp4
> but then it fails with:
> Error initializing an internal MFX session
> Running strace on the command it results that it's looking for the
> libmfxsw64.so library and failing:
> open("/lib/x86_64-linux-gnu/libmfxsw64.so", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
> open("/usr/lib/x86_64-linux-gnu/libmfxsw64.so", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
> open("/lib/libmfxsw64.so", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
> open("/usr/lib/libmfxsw64.so", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
> munmap(0x7f9a55072000, 155122)          = 0
> If I update the LD_LIBRARY_PATH to point to the intel media library in
> /opt/intel/mediasdk it will find the library and then hang.
> I had some hard time finding relevant information on the Internet, so
> I ask if you can help to clarify these points.
> I'll happily provide a few benchmarks and update documentation
> accordingly if I manage to make it work.
> -- 
> FFmpeg = Fancy and Forgiving Mean Problematic Excellent Gymnast
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

It is what and why we do it that matters, not just one of them.
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