Recherche avancée

Sur d’autres sites (7381)

• aacdec_usac : always zero out alpha_q values for stereo streams

  12 juin 2024, par Lynne

  aacdec_usac : always zero out alpha_q values for stereo streams
  The issue is that if a frame has no complex stereo prediction,
  
  the alpha values must all be assumed to be zero if the next frame
  
  has complex prediction and uses delta coding.
  

  • [DH] libavcodec/aac/aacdec_usac.c

• how to fill AvFrame pixel by pixel

  18 mai 2017, par masoud khanlo

  i try to encode opengl output to a mp4 file using ffmpeg but when i want to simply fill AvFrame with pixel colors with this code snippet :

  for (y = 0; y < c->height; y++) {
  
  for (x = 0; x < c->width; x++) {
  
      int offset = 3 * (x + y * c->width);
  
  
  
      if (x > 2* c->width / 3 && x width )
  
      {
  
          frame->data[0][offset + 0] = 0; // B
  
          frame->data[0][offset + 1] = 0; // G
  
          frame->data[0][offset + 2] = 255; // R
  
      } 
  
      else if(x < 2 * c->width / 3 && x > c->width / 3) {
  
          frame->data[0][offset + 0] = 0; // B
  
          frame->data[0][offset + 1] = 255; // G
  
          frame->data[0][offset + 2] = 0; // R
  
      }
  
      else {
  
          frame->data[0][offset + 0] = 255; // B
  
          frame->data[0][offset + 1] = 0; // G
  
          frame->data[0][offset + 2] = 0; // R
  
      }
  
  }

  then i have this video output :

  

  and i had this options for ffmpeg :

  codec : libx264rgb
  & pix_fmt : AV_PIX_FMT_BGR24

  in fact i expect something like this video output :

  

  i’m also new in ffmpeg and i realy dont know advanced stuffs about video encoding ,so anybody knows what is problem ?

• replaygain : correctly parse peak values

  4 avril 2014, par Alessandro Ghedini

  replaygain : correctly parse peak values
  According to the ReplayGain spec, the peak amplitude may overflow and may result
  
  in peak amplitude values greater than 1.0 with psychoacoustically coded audio,
  
  such as MP3. Fully compliant decoders must allow peak overflows.
  Additionally, having peak values in the 0<->UINT32_MAX scale makes it more
  
  difficult for applications to actually use the peak values (e.g. when
  
  implementing clipping prevention) since values have to be rescaled down.
  This patch corrects the peak parsing by removing the rescaling of the decoded
  
  values between 0 and UINT32_MAX and the 1.0 upper limit.
  Signed-off-by : Anton Khirnov <anton@khirnov.net>
  

  • [DBH] doc/APIchanges
  • [DBH] libavformat/replaygain.c
  • [DBH] libavutil/replaygain.h
  • [DBH] libavutil/version.h