[Libav-user] getting CUdeviceptr formats and data

[Mathieu Prevot]

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 ?

regards
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://ffmpeg.org/pipermail/libav-user/attachments/20241122/a32644a2/attachment.htm>