[Libav-user] getting CUdeviceptr formats and data

[Mathieu Prevot]

Le dim. 17 nov. 2024 à 20:57, Mathieu Prevot <mathieu.prevot at gmail.com> a
écrit :

> Hello,
>
> I am using code, based on
> https://github.com/FFmpeg/FFmpeg/blob/master/doc/examples/hw_decode.c,
> but I am not transferring the decoded data to the host, I keep it on the
> device for later use with cuda code (my goal will be to use RGB 8-12 bits
> per channel data).
>
> I could not find a way to get the data format
> ((AVPixelFormat)frame->format translates to: "HW acceleration through CUDA.
> data[i] contain CUdeviceptr pointers exactly as for system memory frames.")
>
> I understand that I have two arrays: frame->data[0] and frame->data[1].
>
> I would like to translate the data into a cuda native structure like:
>
> cudaPitchedPtr CUdeviceptr{};
> CUdeviceptr.ptr = frame->data[0];
> CUdeviceptr.ysize = frame->height;
> CUdeviceptr.xsize = frame->width;
>
> Which is probably wrong, since width==1920 height==1080 and should have
> colors or YUV data.
>
> How to get to know the data format (RGB, BGR, YUV, 8/10/12bits per channel
> etc) and the size of the array ?
> If it is not RGB8 (or 10-12), can I get that through some ffmpeg
> implementation, maybe with an nvdec based function ?
> What is the correct cuda-native data ? cudaPitchedPtr or something else ?
> frame->data[0] is uint8_t, but the array is probably something else in the
> general case; so what is it (as redundancy or extension of "what is the
> data format") ?
>

It seems that  frame->data[0] is the Y component of YUV, if not, one of RGB
channels, but I could not figure out what frame->data[1] is.
Can someone confirm ?
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