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• Revision 43873 : Ne pas boucler infiniment si on n’a pas la bonne frame On teste la frame ...

  25 janvier 2011, par kent1@… — Log

  Ne pas boucler infiniment si on n’a pas la bonne frame
  On teste la frame 50 par défaut plutot que 100

• How to get the format of nvdec video frame from ffmpeg decoding ? How to use it in cuda structures ?

  1er décembre 2024, par Soleil

  I am using code, almost exactly 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).

  


  The interesting part is :

  


  //after decoding/encoding
status = avcodec_receive_frame(avctx, frame);
if (status != AVERROR(EAGAIN) && status != AVERROR_EOF)
    LogMessage(L"frame timestamp: %i\n", (int)frame->best_effort_timestamp);
if (status == AVERROR(EAGAIN) || status == AVERROR_EOF)
{
    av_frame_free(&frame);
    return 0;
}
if (status < 0)
{
    LogMessage(L"Error while decoding\n");
    goto finish;
}
{
    auto descr = AVPixelFormatMap[(AVPixelFormat)frame->format];
    std::wstring dsdescr(descr.begin(), descr.end());
    LogMessage(L"Pixelformat: %s", dsdescr.c_str());

    cudaPitchedPtr CUdeviceptr0{}; // !! hypothetical usage of cudaPitchedPtr !!
    CUdeviceptr0.ptr = frame->data[0];
    CUdeviceptr0.pitch = frame->linesize[0]; //2048 == pitch ?
    CUdeviceptr0.ysize = frame->height; //1080
    CUdeviceptr0.xsize = frame->width; //1920
    cudaPitchedPtr CUdeviceptr1{};
    CUdeviceptr1.ptr = frame->data[1];
    CUdeviceptr1.pitch = frame->linesize[1];
    CUdeviceptr1.ysize = frame->height;
    CUdeviceptr1.xsize = frame->width;
}


  


  I could not find a way to get the data format ((AVPixelFormat)frame->format value is AV_PIX_FMT_CUDA which translates to : "HW acceleration through CUDA. data[i] contain CUdeviceptr pointers exactly as for system memory frames.").

  


  Unfortunately this says nothing about the pixel format. I believe it's YUV but I dot not have more details.

  


  I understand that I have two arrays : frame->data[0] and frame->data[1].

  


  

  1. What is each ?

  


  


  

  • frame->data[0] contains data corresponding to Y or one of RGB channels, and is pitched. When I save that as an BW image, I recognized the image, except that it is one channel.

  


  • frame->data[1] is set but has no data. Hence, this is not part of the image content.

  


  • frame->data[2] is NULL.

  


  


  It seems that U and V are somewhere else.

  


  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 OK but incomplete, since width==1920 height==1080 (I have I think only Y of YUV).

  


  


  2. If this is Y of YUV, where are the U and V data ?

     


  


  3. How to get to know more details about the data format (RGB, BGR, YUV, 8/10/12bits per channel, 444, 422, 420 etc) ?

     


  


  


• Frame delay for variable frame rate video

  1er juin 2015, par RohanG

  I’m working for a video player using ffmpeg for Android. I’m following Dranger FFMpeg tutorial. I’m able to play fixed frame rate videos finely. But have problems with variable frame rate videos. How can I get the delay between frames for a variable frame rate video ?