wiki:

HWAccelIntro


Version 17 (modified by jbrower888, 2 years ago) (diff)

c66x fix wording

FFmpeg provides a subsystem for hardware acceleration.

Hardware acceleration allows to use specific devices (usually graphical card or other specific devices) to perform multimedia processing. This allows to use dedicated hardware to perform demanding computation while freeing the CPU from such computations. Typically hardware acceleration enables specific hardware devices (usually the GPU) to perform operations related to decoding and encoding video streams, or filtering video.

When using FFmpeg the tool, HW-assisted decoding is enabled using through the -hwaccel option, which enables a specific decoder. Each decoder may have specific limitations (for example an H.264 decoder may only support baseline profile). HW-assisted encoding is enabled through the use of a specific encoder (for example nvenc_h264). Filtering HW-assisted processing is only supported in a few filters, and in that case you enable the OpenCL code through a filter option.

There are several hardware acceleration standards API, some of which are supported to some extent by FFmpeg.

VDPAU (Video Decode and Presentation API for Unix)

Developed by NVidia for UNIX/Linux systems. To enable this you typically need the libvdpau development package in your distribution, and a compatible graphic card.

Official website: http://http.download.nvidia.com/XFree86/vdpau/doxygen/html/index.html

Note that VDPAU cannot be used to decode frames in memory, the compressed frames are sent by libavcodec to the GPU device supported by VDPAU and then the decoded image can be accessed using the VDPAU API. This is not done automatically by FFmpeg, but must be done at the application level (check for example the ffmpeg_vdpau.c file used by ffmpeg.c). Also note that with this API it is not possible to move the decoded frame back to RAM, for example in case you need to encode again the decoded frame (e.g. when doing transcoding on a server).

Several decoders are currently supported through VDPAU in libavcodec, in particular MPEG Video, VC-1, H.264, MPEG4.

XvMC

XVideo Motion Compensation. This is an extension of the X video extension (Xv) for the X Window System (and thus again only available only on UNIX/Linux).

Official specification is available here: http://www.xfree86.org/~mvojkovi/XvMC_API.txt

VA-API

Video Acceleration API (VA API) is a non-proprietary and royalty-free open source software library ("libVA") and API specification, initially developed by Intel but can be used in combination with other devices. Linux only: https://en.wikipedia.org/wiki/Video_Acceleration_API

DXVA2

Direct-X Video Acceleration API, developed by Microsoft (supports Windows and XBox360).

Link to MSDN documentation: http://msdn.microsoft.com/en-us/library/windows/desktop/cc307941%28v=vs.85%29.aspx

Several decoders are currently supported, in particular H.264, MPEG2, VC1 and WMV3.

DXVA2 hardware acceleration only works on Windows. In order to build FFmpeg with DXVA2 support, you need to install the dxva2api.h header. For MinGW this can be done by downloading the header maintained by VLC:

http://download.videolan.org/pub/contrib/dxva2api.h

and installing it in the include patch (for example in /usr/include/).

For MinGW64, the dxva2api.h is provided through the pacman repository, and can be installed using one of the two following commands, depending on the architecture:

pacman -S mingw-w64-i686-gcc
pacman -S mingw-w64-x86_64-gcc

To enable DXVA2, use the --enable-dxva2 configure switch.

To test decoding, use the following command:

ffmpeg -hwaccel dxva2 -threads 1 -i INPUT -f null - -benchmark

VDA

Video Decoding API, only supported on MAC. H.264 decoding is available in FFmpeg/libavcodec.

Developers documentation: https://developer.apple.com/library/mac/technotes/tn2267/_index.html

NVENC

NVENC is an API developed by NVIDIA which enables the use of NVIDIA GPU cards to perform H.264 and HEVC encoding. FFmpeg supports NVENC through the nvenc_h264 and nvenc_hevc encoders. In order to enable it in FFmpeg you need to locally install the nvEncodeAPI.h header from the NVENC SDK and configure with --enable-nvenc.

To read more about the supported GPUs and download the NVENC SDK go to the following link: https://developer.nvidia.com/nvidia-video-codec-sdk

OpenCL

Official website: https://www.khronos.org/opencl/

Currently only used in filtering (deshake and unsharp filters). In order to use OpenCL code you need to enable the build with --enable-opencl. An API to use OpenCL API from FFmpeg is provided in libavutil/opencl.h. No decoding/encoding is currently supported (yet).

c66x

Official website: https://github.com/c66x/ffmpeg

By entering in the ffmpeg command line

  -hwaccel c66x [opts]

acceleration (both encode and decode) using PCIe accelerator cards with Texas Instruments c66x CPUs is enabled. The following files from the github c66x site are required:

  • modified ffmpeg.c file (or patch)
  • c66x_accel.h
  • Readme (gives usage and syntax for opts)

More info about the c66x ffmpeg solution is available at http://signalogic.com/ffmpeg.html

External resources