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• ffmpeg output pipeing to named windows pipe

  23 août 2015, par Lucas

  This question is related to my previous question : Converting raw frames into webm live stream

  I want to pipe a video to ffmpeg and read it back through another pipe, but I cannot pipe the output of ffmpeg.exe to a named pipe on windows.

  My definition of the pipes in C# :

  NamedPipeServerStream p_to_ffmpeg;
  
  NamedPipeServerStream p_from_ffmpeg;
  
  p_to_ffmpeg = new NamedPipeServerStream("to_ffmpeg", PipeDirection.Out, 1, PipeTransmissionMode.Byte);
  
  p_from_ffmpeg = new NamedPipeServerStream("from_ffmpeg", PipeDirection.In, 1, PipeTransmissionMode.Byte);

  And then I start ffmpeg.exe in a separate process with the following options : -f rawvideo -vcodec rawvideo -video_size 656x492 -r 10 -pix_fmt rgb24 -i \\.\pipe\to_ffmpeg  -c:v libvpx  -pass 1 -f webm \\.\pipe\from_ffmpeg

  ffmpeg.exe refuses to write to the pipe with the following error : File '\\.\pipe\from_ffmpeg' already exists. Overwrite ? [y/N]

  When I replace the "output pipe" with a file name, it works like charm : -f rawvideo -vcodec rawvideo -video_size 656x492 -r 10 -pix_fmt rgb24 -i \\.\pipe\to_ffmpeg  -c:v libvpx  -pass 1 -f webm output.webm

  How do I get ffmpeg to write to a named pipe in windows ?

  Edit : When I force to write to the pipe with ffmpeg’s -y option, I get the following error : Could not write header for output file #0 (incorrect codec parameters ?): Error number -32 occurred

• FFMPEG providing support for HEVC decoding

  28 novembre 2013, par sam

  FFMPEG v2.1 onwards is providing support for HEVC Decoding. I tried an elementary input bin stream as an input for it and yes i got a corresponding YUV file.

  Now my question is, since i'm just passing an elementary stream as an input, how is the decoder parsing it ?

  I have gone through the /libavformat/hevcdec.c which is supposed to be a demuxer for HEVC.
  I know hevc_probe() is the function in hevcdec.c where it detects if the file can be decoded by the HEVC decoder.

  The definition of hevc_probe() function is given below :

  static int hevc_probe(AVProbeData *p)
  
  {
  
      uint32_t code = -1;
  
      int vps = 0, sps = 0, pps = 0, irap = 0;
  
      int i;
  
  
  
      for (i = 0; i < p->buf_size - 1; i++) {
  
          code = (code << 8) + p->buf[i];
  
          if ((code & 0xffffff00) == 0x100) {
  
              uint8_t nal2 = p->buf[i + 1];
  
              int type = (code & 0x7E) >> 1;
  
  
  
              if (code & 0x81) // forbidden and reserved zero bits
  
                  return 0;
  
  
  
              if (nal2 & 0xf8) // reserved zero
  
                  return 0;
  
  
  
              switch (type) {
  
              case NAL_VPS:        vps++;  break;
  
              case NAL_SPS:        sps++;  break;
  
              case NAL_PPS:        pps++;  break;
  
              case NAL_BLA_N_LP:
  
              case NAL_BLA_W_LP:
  
              case NAL_BLA_W_RADL:
  
              case NAL_CRA_NUT:
  
              case NAL_IDR_N_LP:
  
              case NAL_IDR_W_RADL: irap++; break;
  
              }
  
          }
  
      }
  
  
  
      // printf("vps=%d, sps=%d, pps=%d, irap=%d\n", vps, sps, pps, irap);
  
  
  
      if (vps && sps && pps && irap)
  
          return AVPROBE_SCORE_EXTENSION + 1; // 1 more than .mpg
  
      return 0;
  
  }

  According to whatever i have read, only if this function returns a constant of type AVPROBE_SCORE_EXTENSION, the decoding will proceed. However it is returning AVPROBE_SCORE_EXTENSION+1 Why is it ?

  Also as seen above in the code, they are deciding some type variable from the input bit code obtained and performing increment in the constants like sps, pps, etc. Is the the normal operation that needs to be performed by a parser which can decode an elementary stream ?

  It would be really helpful to everyone if anyone is able to give a brief of a parser of a decoder that can decode an elementary stream.

  Please Help. Thanks in advance.

• qsvenc : cavlc option is only available for h264

  27 novembre 2017, par Li, Zhong

  qsvenc : cavlc option is only available for h264
  Moving option definition to h264 implementation and fixing command line defaults
  
  in order to properly respect cavlc input value
  Signed-off-by : Zhong Li <zhong.li@intel.com>
  
  Signed-off-by : Maxym Dmytrychenko <maxim.d33@gmail.com>
  

  • [DBH] libavcodec/qsvenc.c
  • [DBH] libavcodec/qsvenc.h
  • [DBH] libavcodec/qsvenc_h264.c