[Libav-user] getting CUdeviceptr formats and data

[Mathieu Prevot]

Le ven. 22 nov. 2024 à 13:55, Mathieu Prevot <mathieu.prevot at gmail.com> a
écrit :

>
> Le mer. 20 nov. 2024 à 18:03, Mathieu Prevot <mathieu.prevot at gmail.com> a
> écrit :
>
>>
>>
>> Le mar. 19 nov. 2024 à 00:39, Mathieu Prevot <mathieu.prevot at gmail.com>
>> a écrit :
>>
>>>
>>>
>>> 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 ?
>>>
>>
>> I got no answer from libav-user@, maybe is it a question for
>> ffmpeg-devel@ (not subscribed, please cc) ?
>>
>
> There seems to be no other data except that of `frame->data[0]`.
>
> I verified, there is nothing beyond `frame->data[0] +
> frame->linesize[0]*frame->height`.
>
> frame->data[1] has another address but there is no data.
>
> frame->buf[0]->data and frame->extended_data  both point to the same
> address as frame->data[0].
>
> no side_data or extended_buf,
>
> opaque_ref is NULL
>
> frame->ch_layout->order is AV_CHANNEL_ORDER_UNSPEC
>
> In the end, it comes down to this questions:
>
> 1. where are UV data of YUV when decoded by cuda ? Y is at frame->data[0].
> 2. frame->linesize[1] is set too, what is this for ?
>

Anyone ?
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