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diff --git a/Software/Beignet/howto/libva-buffer-sharing-howto.mdwn b/Software/Beignet/howto/libva-buffer-sharing-howto.mdwn new file mode 100644 index 00000000..fe64d73a --- /dev/null +++ b/Software/Beignet/howto/libva-buffer-sharing-howto.mdwn @@ -0,0 +1,67 @@ +Libva Buffer Sharing HowTo +========================== + +Beignet has extensions (clCreateBufferFromLibvaIntel/clCreateImageFromLibvaIntel) +to share gpu buffer object with libva. So users can utilize OpenCL to do processing +on VASurface or VABuffer without buffer copy. + +Prerequisite +------------ + +Libva api version >= 0.36.0. Please check your libva api version by command +`pkg-config --modversion libva`. + +Steps +----- + +In order to use the extension clCreateBufferFromLibvaIntel/clCreateImageFromLibvaIntel +in your program, please follow the steps as below (We have added an example of using +clCreateImageFromLibvaIntel, please read next section for details): + +- Get the address of this extension by the function: + clGetExtensionFunctionAddress("clCreateBufferFromLibvaIntel") + or clGetExtensionFunctionAddress("clCreateImageFromLibvaIntel") + +- Invoke vaAcquireBufferHandle to get VASurface/VABuffer's handle, which you want + to do processing by OpenCL. + +- Use clCreateBufferFromLibvaIntel/clCreateImageFromLibvaIntel to create corresponding + cl memory object from VASurface/VABuffer's handle. If you create a normal VASurface, + you should use clCreateImageFromLibvaIntel to create a cl image object from VASurface, + because VASurface is a tiling gpu buffer object. The only case you should use + clCreateBufferFromLibvaIntel to create a cl buffer object from VASurface is that: The + VASurface is created from an external untiling gpu buffer object. And You should use + clCreateBufferFromLibvaIntel to create a cl buffer object from VABuffer. + +- Use OpenCL to do post-processing. + +- Release this cl buffer object by clReleaseMemObject. + +- Unlock this VABuffer by vaReleaseBufferHandle. + +Sample code +----------- + +We have developed an example of using clCreateImageFromLibvaIntel in examples/libva_buffer_sharing +directory. This example read a source nv12 file to a VASurface, and create a target VASurface. +Then create corresponding cl image objects from them. After using ocl to do a mirror effect +post-processing on this source surface, target VASurface is shown on screen by default. + +- Add option -DBUILD_EXAMPLES=ON to enable building examples when running cmake, such as: + `> mkdir build` + `> cd build` + `> cmake -DBUILD_EXAMPLES=ON ../` + +- Build source code: + `> make` + +- Run: + `> cd examples` + `> . ../utests/setenv.sh` + `> ./example-libva_buffer_sharing` + +In addition, you can choose to save the result as a nv12 file. You can use gst-launch-1.0 to see +the result. Just install gstreamer1.0-plugins-base, gstreamer1.0-plugins-bad and +gstreamer1.0-x by apt on Ubuntu. Then running the following command: + `> gst-launch-1.0 filesrc location=file_name ! videoparse format=nv12 width=xxx height=xxx \ + ! imagefreeze ! videoconvert ! video/x-raw, format=BGRx ! ximagesink` |