Extend the internal CUDA frames context (CUDAFramesContext) to manage
block-linear CUarray surfaces alongside the existing pitched-linear
allocations.
When the frames context format is AV_PIX_FMT_CUARRAY, the caller
(e.g. NVDEC) can fill cuarray_desc and cuarray_num_surfaces before
calling av_hwframe_ctx_init(), which then allocates the CUarray
surfaces.
Also add cuda_transfer_data_from_cuarray() to support hwdownload
from CUarray frames to host memory via cuMemcpy2DAsync.
Co-authored-by: Diego de Souza <ddesouza@nvidia.com>
Signed-off-by: Diego de Souza <ddesouza@nvidia.com>
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