Strange performance results

[zezinho]

Summary of the bug:
Encoding with VAAPI is much slower if sound is converted. Launching another ffmpeg dedicated to the sound conversion gives much better results.

The test was done with 9th generation Intel HD500 in a Celeron N3350 and a 1080p@24 and 18Mb/s file.

With the example below, I get 60fps so it is 2.42x speed. Removing the acodec copy option, it is converted to vorbis, speed drops to 42fps (1.41x).

The strange point is that launching another simultaneous ffmpeg to drops the video and converts to vorbis, I get normal speed for this CPU : 5.5x and the other ffmpeg keeps at 2.42x.

So it seems using VAAPI along with Vorbis slows down both codecs.

How to reproduce:

% ffmpeg \
  -hwaccel vaapi \
  -vaapi_device /dev/dri/renderD128 \
  -i input.mkv \
  -vf 'format=nv12,hwupload,scale_vaapi=w=1366:h=768' \
  -vcodec h264_vaapi \
  -acodec copy \
  -qp 23 \
  output.mkv
ffmpeg version 3.2.4
built on gcc 5.4.0 (Mageia 6 package)

[Carl Eugen Hoyos]

Is this issue reproducible with current FFmpeg git head?

[zezinho]

Replying to cehoyos:

Is this issue reproducible with current FFmpeg git head?

Sorry, I have no easy way to try on git version. But it is version 3.2.4 that I have used, even if it is not avaliable in TRAC menu...

[Carl Eugen Hoyos]

Replying to zezinho:

Replying to cehoyos:

Is this issue reproducible with current FFmpeg git head?

Sorry, I have no easy way to try on git version.

Why?
Are there no FFmpeg binaries offered for your operating system?

[zezinho]

Replying to cehoyos:

Replying to zezinho:

Replying to cehoyos:

Is this issue reproducible with current FFmpeg git head?

Sorry, I have no easy way to try on git version.

Why?
Are there no FFmpeg binaries offered for your operating system?

Unfortunately, they have no VAAPI enabled :

ffmpeg version N-83692-gb8a7dcbde2-static ​http://johnvansickle.com/ffmpeg/ Copyright (c) 2000-2017 the FFmpeg developers

built with gcc 5.4.1 (Debian 5.4.1-5) 20170205
configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc-5 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gray --enable-libass --enable-libfreetype --enable-libfribidi --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libzimg
libavutil 55. 47.100 / 55. 47.100
libavcodec 57. 81.100 / 57. 81.100
libavformat 57. 66.102 / 57. 66.102
libavdevice 57. 3.100 / 57. 3.100
libavfilter 6. 74.100 / 6. 74.100
libswscale 4. 3.101 / 4. 3.101
libswresample 2. 4.100 / 2. 4.100
libpostproc 54. 2.100 / 54. 2.100

[AVHWDeviceContext @ 0x4a61ec0] No VA display found for device: /dev/dri/renderD128.
[vaapi @ 0x312f1e0] Failed to create a VAAPI device

[jkqxz]

This is an expected consequence of the single-threaded nature of the ffmpeg utility combined with synchronous behaviour in the Intel VAAPI driver (it doesn't use the CPU while encoding, but it still blocks the calling thread waiting for it to finish).