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• FFMPEG : Explain parameters of any codecs function pointers

  7 juillet 2014, par Zax

  I’m going through the article, How to integrate a codec in FFMPEG multimedia framework.
  According to it, every codec needs to have 3 basic functions to be defined and these functions are assigned to function pointers of the structure AVCodec.

  The 3 function pointers specified in the above article are :

  .init -> takes care of allocations and other initializations
  
  
  
  .close -> freeing the allocated memory and de-initializations
  
  
  
  .decode -> frame by frame decoding.

  For the function pointer .decode, the function assigned is :

  static int cook_decode_frame(AVCodecContext *avctx,
  
              void *data, int *data_size,
  
              uint8_t *buf, int buf_size) {
  
  ...

  The details of these parameters are specified in the above article. However, in the latest code, when the same function is taken as an example, its declaration is as shown below :

  static int cook_decode_frame(AVCodecContext *avctx, void *data,
  
                               int *got_frame_ptr, AVPacket *avpkt)

  I need to perform some mapping operations on the memory. So, i request if anyone could kindly explain the above parameters in the function declarations. Also, which parameter has the input buffer for decoding the frame ? And after decoding a frame, to which parameter is the decoded frame mapped ?

• Hardware Accelerated H264 Decode using DirectX11 in Unity Plugin for UWP

  8 janvier 2019, par rohit n

  I’ve built an Unity plugin for my UWP app which converts raw h264 packets to RGB data and renders it to a texture. I’ve used FFMPEG to do this and it works fine.

  int framefinished = avcodec_send_packet(m_pCodecCtx, &packet);
  
  framefinished = avcodec_receive_frame(m_pCodecCtx, m_pFrame);
  
  // YUV to RGB conversion and render to texture after this

  Now, I’m trying to shift to hardware based decoding using DirectX11 DXVA2.0.

  Using this : https://docs.microsoft.com/en-us/windows/desktop/medfound/supporting-direct3d-11-video-decoding-in-media-foundation

  I was able to create a decoder(ID3D11VideoDecoder) but I don’t know how to supply it the raw H264 packets and get the YUV or NV12 data as output.
  (Or if its possible to render the output directly to the texture since I can get the ID3D11Texture2D pointer)

  so my question is, How do you send the raw h264 packets to this decoder and get the output from it ?

  Also, this is for real time operation so I’m trying to achieve minimal latency.

  Thanks in advance !

• How do I create and initialise a DXGI_FORMAT_NV12 resource in DX12 (source is AVFrame)

  5 janvier 2023, par mike

  I'm trying to create an NV12 resource as source for a video encoder in DX12. While I intend to eventually populate a resource from GPU, what I'm trying to do now is take an ffmpeg AVFrame I already have (in AV_PIX_FMT_YUV420P format) and create a texture in DXGI_FORMAT_NV12 format using that data.
  

  


  I understand the NV12 format (https://learn.microsoft.com/en-us/windows/win32/medfound/recommended-8-bit-yuv-formats-for-video-rendering#nv12) has U and V interleaved while the AV_PIX_FMT_YUV420P doesn't.

  


  My main question is what does the D3D12_RESOURCE_DESC look like for an NV12 texture - do I tell it I need more than one array/mip level to make it planar ? Or do I just give it a single memory address with both planes layed out as per the NV12 format, and it figures out subresources for me based on the format ?
  
I understand that to read the data I define two SRVs, one for Y mapped to the Red channel and a second for U and V, but it's how I initialise it that's confusing me.