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• How to save data of packet.data in ffmpeg using c language ?

  10 juin 2015, par patrick

  I’m try to build an app in c that extract audio from video and save it as audio file. I write the below code. I’m able to extract the audio but now the problem is how to save it. Thanks in advance.

  My code is :

  int main(int argc, char *argv[]) {
  
  AVFormatContext *pFormatCtx = NULL;
  
  int             i;
  
  AVCodecContext  *pCodecCtx = NULL;
  
  AVCodec         *pCodec = NULL;
  
  AVFrame         *pFrame = NULL; 
  
  AVPacket        packet;
  
  
  
  AVDictionary    *optionsDict = NULL;
  
  
  
  if(argc < 2) {
  
  printf("Please provide a movie file\n");
  
  return -1;
  
  }
  
  av_register_all();
  
  if(avformat_open_input(&pFormatCtx, argv[1], NULL, NULL)!=0)
  
  return -1; 
  
  
  
  if(avformat_find_stream_info(pFormatCtx, NULL)<0)
  
  return -1; 
  
  
  
  av_dump_format(pFormatCtx, 0, argv[1], 0);
  
  
  
  int audioStream=-1;
  
  for(i=0; inb_streams; i++)
  
      if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_AUDIO) {
  
          audioStream=i;
  
          break;
  
      }
  
  if(audioStream==-1)
  
  return -1; 
  
  
  
  pCodecCtx=pFormatCtx->streams[audioStream]->codec;
  
  
  
  pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
  
  if(pCodec==NULL) {
  
      fprintf(stderr, "Unsupported codec!\n");
  
      return -1; // Codec not found
  
  }
  
  
  
  if(avcodec_open2(pCodecCtx, pCodec, &optionsDict)<0)
  
  return -1; 
  
  
  
  pFrame=avcodec_alloc_frame();
  
  packet.data = NULL;
  
  packet.size = 0;
  
  
  
  while(av_read_frame(pFormatCtx, &packet)>=0) {
  
      int got_frame = 0;
  
      int ret = avcodec_decode_audio4(pCodecCtx, pFrame, &got_frame, &packet);
  
      if(got_frame && packet.stream_index==audioStream) {
  
          //save result but how???
  
      }
  
      av_free_packet(&packet);
  
  }
  
  av_free(pFrame);
  
  avcodec_close(pCodecCtx);
  
  avformat_close_input(&pFormatCtx);
  
  return 0;
  
  }

• ffmpeg : how to save h264 raw data as mp4 file

  15 avril 2016, par monkid

  I encode h264 data by libavcodec.
  ex.

  while (1) {
  
    ...
  
    avcodec_encode_video(pEnc->pCtx, OutBuf, ENC_OUTSIZE, pEnc->pYUVFrame);
  
    ...
  
  }

  If I directly save OutBuf data as a .264 file, it can`t be play by player. Now I want to save OutBuf

  as a mp4 file. Anyone know how to do this by ffmpeg lib ? thanks.

• Linux/bash - ffmpeg - encode file with half bitrate and half resolutio

  3 octobre 2014, par user1209216

  I have some video file. I need to re-encode this in this way :
   result file bitrate is 2x lower than original
   result file resolution is 2x lower (witdth and height)
   audio codec - copied from source, video codec : h264

  I know how to encode with hardcoded bitrate/resolution and audio copy. However, I have no idea how to make that values as half of input file parameters. Can I do this with ffmpeg ?