Enable vaapi, to support hardware acceleration

[qmfrederik]

This PR adds the --enable-vaapi flag, and builds FFmpeg with support for (Intel) hardware acceleration.
The Ubuntu, CentOS and Alpine images have also been updated to include the build-time vaapi dependencies.

[jrottenberg]

runtime dependency ?

Just for ubuntu ? That would explain the failure on https://travis-ci.org/jrottenberg/ffmpeg/builds/389354692 though.

[GnaphronG]

This should be move into the base container to avoid an extra layer

[jrottenberg]

Thanks a lot for your contribution it was on my todo list for a while and was requested like on #27

[qmfrederik]

@jrottenberg I've fixed the CentOS and Alpine builds by installing libva in the target container. Travis shows a couple of errors; that seems to be because of file download issues.

[jrottenberg]

It looks great, thank you.

One more commit andI'll merge : remove templates/.Dockerfile-env.swp
https://github.com/jrottenberg/ffmpeg/pull/106/files#diff-c479c96df0fcf8f4474e645d4d473888

[jrottenberg]

oh !

The following NEW packages will be installed:
  i965-va-driver libbsd0 libdrm-amdgpu1 libdrm-common libdrm-intel1
  libdrm-nouveau2 libdrm-radeon1 libdrm2 libedit2 libelf1 libffi6 libllvm5.0
  libpciaccess0 libsensors4 libva-drm1 libva1 libx11-xcb1 libxau6
  libxcb-dri2-0 libxcb-dri3-0 libxcb-present0 libxcb-sync1 libxcb-xfixes0
  libxcb1 libxdmcp6 libxshmfence1 mesa-va-drivers va-driver-all
0 upgraded, 28 newly installed, 0 to remove and 0 not upgraded.
Need to get 15.9 MB of archives.
After this operation, 74.5 MB of additional disk space will be used.

I wonder if we should make a variant for that build ...

[qmfrederik]

@jrottenberg Using --no-install-recommends seems to fix this:

The following additional packages will be installed:
  libdrm-common libdrm2
Recommended packages:
  va-driver-all | va-driver
The following NEW packages will be installed:
  libdrm-common libdrm2 libva-drm1 libva1
0 upgraded, 4 newly installed, 0 to remove and 3 not upgraded.
Need to get 89.0 kB of archives.
After this operation, 356 kB of additional disk space will be used.

The recommended part contains the i695-va-driver, which needs to run on the host, not inside the Docker container, so I think this is a safe change to make.

[jrottenberg]

ok I really want to merge it , but it touches too many images, would you be ok to create a new variant based on ubuntu named :

• jrottenberg/ffmpeg:3.3-vaapi
• jrottenberg/ffmpeg:4.0-vaapi
  etc

[qmfrederik]

Yes, sure, I'm using the Ubuntu variant anyway.