[Libav-user] How to use an existing CUDA context for decoding

[joep]

Hello,



I am trying to create a program that does the following:

1. decode frames with cuvid

2. run CUDA kernels on the decoded frames

3. encode result with nvenc



In order to do step 2, I need the CUDA kernels to access the decoded frame which should be stored in the GPU memory.

For this I think I need to provide the CUDA CUcontext to ffmpeg and give the pointer to the decoded frame to the kernel.


I could not find any documentation about this topic.

In the ffmpeg docs I see the AVCodecContext has hw_device_ctx which is a AVHWDeviceContext.

AVHWDeviceContext has a hwctx field which can be a AVCUDADeviceContext.

AVCUDADeviceContext has a cuda_ctx field which is a CUcontext.



So I think I need to create a AVHWDeviceContext and set it on the AVCodecContext before calling avcodec_open2.

Are my assumptions right?

And how can I create a AVHWDeviceContext with the correct hwctx?



Thanks,

Joep
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