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• [ffmpeg C++ API] : How to copy a music file's cover image into another music file ?

  22 avril 2022, par Ananta

  I am having difficulties in copying a source music file's cover image into a destination music file. These two music files are in different formats (i.e, either mp3, flac, wav, or wma, different sampling rate). How should I implement the code for this ? I created a minimal code for this task below :

  


  const char* src_path = "source.mp3";
const char* dest_path = "destination.flac";
AVPacket src_pic; 

// open the source path
AVFormatContext *src_ctx = avformat_alloc_context();
avformat_open_input(&src_ctx, src_path, NULL, NULL);

// find the first attached picture, if available
for (i = 0; i < src_ctx->nb_streams; i++)
   if (src_ctx->streams[i]->disposition & AV_DISPOSITION_ATTACHED_PIC) {
      src_pic = src_ctx->streams[i]->attached_pic;

// open the destination path
AVFormatContext *dest_ctx = avformat_alloc_context();
avformat_open_input(&dest_ctx, dest_path, NULL, NULL);

// Then, how to embed the 'src_pic' into 'dest_ctx'?

  


  


• ppc : reduce overreads when loading 8 pixels in altivec dsp functions

  13 février 2014, par Janne Grunau

  ppc : reduce overreads when loading 8 pixels in altivec dsp functions
  Altivec can only load naturally aligned vectors. To handle possibly
  
  unaligned data a second vector is loaded from an offset of the original
  
  location and the data is recovered through a vector permutation.
  
  Overreads are minimal if the offset for second load points to the last
  
  element of data. This is 7 for loading eight 8-bit pixels and overreads
  
  are reduced from 16 bytes to 8 bytes if the pixels are 64-bit aligned.
  
  For unaligned pixels the overread is reduced from 23 bytes to 15 bytes
  
  in the worst case.
  

  • [DH] libavcodec/ppc/dsputil_altivec.c

• How to stream the video from one PC to another with an acceptable quality and synchronization ?

  15 juin 2021, par ErickSkrauch

  I have the following task : to organize the broadcast of several gamers on the director's computer, which will switch the image to, to put it simply, the one who currently has more interesting gameplay.

  


  The obvious solution would be to raise an RTMP server and broadcast to it. We tried that. The image quality clearly correlates with the bitrate of the broadcast, but the streams aren't synchronized and there is no way to synchronize them. As far as I know, it's just not built into the RTMP protocol.

  


  We also tried streaming via UDP, SRT and RTSP protocols. We got minimal delay but a very blurry image and artifacts from lost packets. It feels like all these formats are trying to achieve constant FPS and sacrifice the quality.

  


  What we need :

  


  

  • A quality image.

  


  • Broken frames can be discarded (it's okay to have not constant FPS).

  


  • Latency isn't important.

  


  • The streams should be synchronized within a second or two.

  


  


  There is an assumption that broadcasting on UDP should be a solution, but some kind of intermediate buffer is needed to provide the necessary broadcasting conditions. But I don't know how to do that. I assume that we need an intermediate ffmpeg instance, which will read the incoming stream, buffer it and publish the result to some local port, from which the picture will be already taken by the director's OBS.

  


  Is there any solution to achieve our goals ?