How Encode/Decode/Transcode  HEVC/H.264 by Intel Quick Sync Video HW (QSV) via ffmpeg

Content

Encode HEVC/H.265 stream

Encode H264/AVC

Decode HEVC and H.264 streams

Transcode from H.264/AVC to HEVC/H.265

Appendix: What’s a gain of HEVC over H.264/AVC?

 

 

First of all pls. check that your Intel GPU supports HEVC/H.265 encoding and decoding by visiting the following site:

       https://software.intel.com/en-us/articles/encode-and-decode-capabilities-for-7th-generation-intel-core-processors-and-newer

Check whether your ffmpeg supports QSV with ‘-hwaccels’ option (if not try to reconfigure and re-compile it), i get the following print :

ffmpeg -hwaccels
ffmpeg version N-91655-g7e0df5910e Copyright (c) 2000-2018 the FFmpeg developers
built with gcc 8.2.1 (GCC) 20180813
configuration: –enable-gpl –enable-version3 –enable-sdl2 –enable-fontconfig –enable-gnutls –enable-iconv –enable-libass –enable-libbluray –enable-libfreetype –enable-libmp3lame –enable-libopencore-amrnb –enable-libopencore-amrwb –enable-libopenjpeg –enable-libopus –enable-libshine –enable-libsnappy –enable-libsoxr –enable-libtheora –enable-libtwolame –enable-libvpx –enable-libwavpack –enable-libwebp –enable-libx264 –enable-libx265 –enable-libxml2 –enable-libzimg –enable-lzma –enable-zlib –enable-gmp –enable-libvidstab –enable-libvorbis –enable-libvo-amrwbenc –enable-libmysofa –enable-libspeex –enable-libxvid –enable-libaom –enable-libmfx –enable-amf –enable-ffnvcodec –enable-cuvid –enable-d3d11va –enable-nvenc –enable-nvdec –enable-dxva2 –enable-avisynth
libavutil      56. 19.100 / 56. 19.100
libavcodec     58. 24.101 / 58. 24.101
libavformat    58. 17.103 / 58. 17.103
libavdevice    58.  4.101 / 58.  4.101
libavfilter     7. 26.100 /  7. 26.100
libswscale      5.  2.100 /  5.  2.100
libswresample   3.  2.100 /  3.  2.100
libpostproc    55.  2.100 / 55.  2.100
Hardware acceleration methods:
cuda
dxva2
qsv
d3d11va
qsv
cuvid

 

By the way you can disable printing ffmpeg banner by -hide_banner:

ffmpeg -hide_banner -hwaccels

Hardware acceleration methods:
cuda
dxva2
qsv
d3d11va
qsv
cuvid

 

 

Encode HEVC/H.265 stream

To encode HEVC/H.265 by QSV hw-encoder you need instruct ffmpeg to use hw-accelerator ‘qsv’ by ‘-hwaccel qsv’, apply HEVC hw-encoder by ‘c:v hevc_qsv’, in addition you need load  hevc plugin (see the example command line).

Input:  raw video in the format yuv420p

Target bitrate:  10 Mbps

ffmpeg  -hwaccel qsv  -s 1920×1080 -pix_fmt yuv420p  -i test420p.yuv -c:v hevc_qsv -load_plugin hevc_hw  -b 10M  -y test.h265

If encoding stuck or the following weird messages printed:

[hevc_qsv @ 000001ff451d40c0] Selected ratecontrol mode is not supported by the QSV runtime. Choose a different mode.
Error initializing output stream 0:0 — Error while opening encoder for output stream #0:0 – maybe incorrect parameters such as bit_rate, rate, width or height

try ‘ -init_hw_device qsv=hw -filter_hw_device hw ‘ , e.g.

ffmpeg -init_hw_device qsv=hw -filter_hw_device hw -v verbose -f rawvideo -video_size 1920×1080 -pix_fmt yuv420p  -i test420.yuv  -c:v hevc_qsv -load_plugin hevc_hw  -preset veryfast output.h265

Note:

• HEVC encoding rate of 1080p on Intel Iris Plus Graphics GPU is about 100 fps

 

Encode H264/AVC

Use -c:v h264_qsv

ffmpeg -hwaccel qsv -s 1920×1080 -pix_fmt yuv420p -i  crowdrun1080p50fps.yuv -c:v h264_qsv -b 10M -y test_qsv.h264

         …

        frame= 500 fps=147 q=30.0 Lsize= 25930kB time=00:00:19.92 bitrate=10663.5kbits/s speed=5.86x

 

To get closed-gops, e.g. each gop is 50 frames use ‘-g 50 -idr_interval 0’:

ffmpeg -hwaccel qsv -s 1920×1080 -pix_fmt yuv420p -i crowd_1920x1080_50fps.yuv -c:v h264_qsv  -b:v 10M -maxrate 15M -g 50 -idr_interval 0 -y crowd_qsv.h264

Note:

• H264 encoding rate of 1080p on Intel Iris Plus Graphics GPU is about 150 fps

 

 

Decode HEVC and H.264 streams

Example to decode 100 frames:

ffmpeg -hwaccel qsv -i test_3840×2160.h265   -pix_fmt yuv420p -vframes 100     test_3840x2160.yuv

if you get the following error (apparently you use recent version of ffmpeg):

Impossible to convert between the formats supported by the filter

Don’t panic, use ‘-vf hwdownload,format=nv12’,  bear in mind that in NV12 pixel format each frame consists of two planes: Y plane and UV plane where U and V values are interleaved, nv12 is equal in size with yuv420p. 

hevc case:  in the following  example input hevc is encapsulated in mpegts format:

ffmpeg -hwaccel qsv -i test.ts   -vf hwdownload,format=nv12    -pix_fmt yuv420p -vframes 100 -y test_384x320.yuv

 

h264 case: use ‘-vf hwdownload,format=nv12’:

ffmpeg -hwaccel qsv -i crowd.h264 -vf hwdownload,format=nv12 -pix_fmt yuv420p -vframes 400 -y crowd_1920x1080.yuv

GPU usage:

 

 

 

Transcode from H.264/AVC to HEVC/H.265

Example [transcode from h264/avc to h265/hevc with lowering the bitrate to 5Mbps]:

ffmpeg -hwaccel qsv -c:v h264_qsv -i test.h264 -c:v hevc_qsv -load_plugin hevc_hw -b 5M -y test.h265

Notice that ‘-c:v h264_qsv‘ is necessary (despite the input h264 stream is not re-encoded, it’s decoded), otherwise ffmpeg is stuck.

 

 

 

Appendix: What’s a gain of HEVC over H.264/AVC?

I often hear or read that HEVC/H.265 provides 50% (the magic number) improvement in bitrate over AVC/H.264. Perhaps, on specific scenes HEVC is better in bitrate by 50% against H264.

However, according to the technical paper written by respected researchers T. Wiegand, W.-J. Han, B. Bross, J.-R. Ohm, and G.J. Sullivan,

“High efficiency video coding (HEVC) text specification draft 7” JCTVC-I1003, improvement of HEVC against H264/AVC are more modest:

33% improvement in bit-rate without compromising video quality for random-access configuration

22% improvement in bit-rate for All-Intra configuration.