[FFmpeg-devel] [RFC] QSV support clarifications

Stefano Sabatini stefasab at gmail.com
Mon Oct 12 20:10:04 CEST 2015

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:

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

2. The mfx_dispatch library compiles fine on my system, but then I
wonder how it is supposed to reference the Intel Media library:


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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