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Hardware Accelerated Decoding

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WangBin edited this page Feb 23, 2019 · 19 revisions

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VA-API

Install vainfo libva-dev, libva-intel-vaapi-driver(intel gpu), xvba-va-driver(ATI), vdpau-va-driver(NVIDIA)

If vainfo works, then QtAV should work with VA-API

EGL

Since Qt5.5, you can enable EGL by setting environment var QT_XCB_GL_INTEGRATION=xcb_egl. player and QMLPlayer have EGL configuration too. If EGL is used, VA-API decoding and OpenGL rendering can get the best performance. NVIDIA GPUs currently do not support EGL+VA-API. AMD is not tested.

If EGL is used, you can use zero copy for X11, DRM display. Otherwise, zero copy is only available for X11 and GLX display.

CUDA

OpenGL desktop mode supports 0-copy. To use 0-copy, make sure your program runs with NVIDIA GPU (on Optimus). DirectCopy is the default. DirectCopy mode is fast enough, faster than potplayer, lavfilters+mpc, and may be the fastest one. ZeroCopy mode is even faster.

Linux

On ubuntu 16.04, nvidia-361-updates should work.

Windows

Install latest nvidia driver.

DXVA/D3D11

D3D11 decoder is supported for windows store. Run in OpenGL ES2 mode (ANGLE) to enable 0-copy. DXVA 0-copy in OpenGL desktop mode only supports some new intel GPUs in my tests, maybe also supports AMD.

Developer

Build

Code

Use AVPlayer.setVideoDecoderPriority(...) to set hw decoders. For example player->setVideoDecoderPriority(QStringList() << "CUDA" << "D3D11" << "DXVA" << "VAAPI" << "VideoToolbox" << "FFmpeg") will try to use hardware decoder, then fallback to ffmpeg software decoder if no hardware decoder is supported for the video.

Each decoder has it's own options which can be changed by AVPlayer.setOptionsForVideoCodec(...). The default is good enough. The following is how to change decoder options

CUDA:

QVariantHash cuda_opt;
cuda_opt["surfaces"] = 0; //key is property name, case sensitive
cuda_opt["copyMode"] = "ZeroCopy"; // default is "DirectCopy"
QVariantHash opt;
opt["CUDA"] = cuda_opt; //key is decoder name, case sensitive
player.setOptionsForVideoCodec(opt);

Since QtAV1.8, CUDA decoder supports ZeroCopy. Run your program with NVIDIA GPU if you have multiple GPUs.

VA-API:

QVariantHash va_opt;
va_opt["display"] = "X11"; //"GLX", "X11", "DRM"
va_opt["copyMode"] = "ZeroCopy"; // "ZeroCopy", "OptimizedCopy", "GenericCopy". Default is "ZeroCopy" if possible
QVariantHash opt;
opt["VAAPI"] = va_opt; //key is decoder name, case sensitive
player.setOptionsForVideoCodec(opt);

Copy Mode

Copy mode for GPU decoders was introduced since 1.5.0. Copy mode can be ZeroCopy, LazyCopy, OptimizedCopy and GenericCopy.

  • ZeroCopy: No data read back from GPU. Directly render the decoded data on GPU. It's the most efficient way. Now it's supported by
    • CUDA
    • VA-API with libva-x11 and libva-glx. It may not work for vdpau backend.
    • VDA(OSX), VideoToolbox(OSX, iOS>=8)
    • DXVA with ANGLE. (Desktop OpenGL is not stable now)
  • LazyCopy: Used in VDA and VideoToolBox
  • OptimizedCopy: Use SSE4.1 for x86 used by DXVA and VA-API(VDA crashes), and NEON for CedarV. SSE4.1 does not work for some GPUs, e.g. NVIDIA GS8400
  • GenericCopy: Use memcpy

Status

  • D3D11
  • Copy
  • OpenGL WGL (implemented in MDK SDK)
  • EGL RGB via ANGLE (D3D11)
  • EGL YUV via ANGLE (implemented in MDK SDK)
  • DXVA
  • Copy
  • EGL via ANGLE (D3D9)
  • EGL DXVAHD
  • OpenGL WGL
  • CUDA
  • Copy
  • EGL (implemented in MDK SDK)
  • OpenGL
  • VA-API
  • Copy
  • EGL DMA/DRM
  • EGL TFP
  • GLX TFP
  • VDA
  • Copy
  • OpenGL
  • VideoToolbox
  • Copy
  • OSX CGL
  • iOS EAGL
  • Copy
  • GLX
  • EGL(X11) TFP
  • OMX
  • RPI
  • MMAL
  • MMAL + EGL (brcm extensions, implemented in MDK SDK)
  • SUNXI Cedarv
  • COPY
  • EGL UMP (implemented in MDK SDK)
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