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• lavfi/select/scene : move out convoluted sad variable init from loop.

  13 octobre 2012, par Clément Bœsch

  lavfi/select/scene : move out convoluted sad variable init from loop.

• Watch multi-stream video file while being recorded by ffmpeg

  20 janvier 2020, par Luke Gorrie

  I am using ffmpeg to record four 1080p video streams simultaneously and I would like to view these streams in real time while they are being recorded. Ideally I would like to view them from a separate machine, using some convenient Linux data sharing method like ssh/sshfs/..., but that is a nice-to-have. Is there a practical way to accomplish this ?

  The ffmpeg recording command that I currently use is like this :

  ffmpeg \
  
    -f v4l2 -i $cam0 \
  
    -f v4l2 -i $cam1 \
  
    -f v4l2 -i $cam2 \
  
    -f v4l2 -i $cam3 \
  
    -f matroska \
  
    -map 0 \
  
    -map 1 \
  
    -map 2 \
  
    -map 3 \
  
    -c copy \
  
    $output.mkv

  My problem would be solved if I could use a command like ffplay or vlc to play one or more of the video streams, always tracking close to the end of the stream, playing more as data becomes available. I haven’t found such an option though.

  One alternative might be to have the recording ffmpeg process also tile the four 1080p videos into one 4K grid and pipe that to ffplay. Then I could at least preview on the same machine that is recording. I have not been able to work out the right ffmpeg command to do the tiling though and would appreciate an example.

• ffmpeg-android Extract Audio From Digital Container Format

  15 août 2013, par user2685548

  I make program extracts audio from Digital Container Format (DCF).
  I want to obtain an encoded audio file.
  so, I think that I can write to file only audio stream packet.

  Some DCF file work well, but some files does not work.

  Please, can you help me to find a problem ?

  // src  -- is DCF
  
  // dest -- is going to write file
  
  int ExtractAudio(const char src[], const char dest[]) {
  
      av_register_all();
  
      avcodec_register_all();
  
  
  
      __android_log_print(ANDROID_LOG_DEBUG, "test", "dest : %s", dest);
  
      __android_log_print(ANDROID_LOG_DEBUG, "test", "src : %s", src);
  
  
  
      //파일을 열고 컨텍스트에 파일 형식을 불러온다.
  
      AVFormatContext * pInputFormatContext = NULL;
  
      int err = avformat_open_input(&pInputFormatContext, src, NULL, NULL);
  
      if (err < 0) {
  
          __android_log_print( ANDROID_LOG_DEBUG, "test",
  
              "avformat_open_input Err! %d",err);
  
          return 0;
  
      }
  
  
  
      FILE *destFile = fopen(dest, "wb");
  
      FILE *srcFile = fopen(src, "rb");
  
      if (destFile == NULL || srcFile == NULL) {
  
          __android_log_print(ANDROID_LOG_DEBUG, "test", "fopen Err!");
  
          __android_log_print(ANDROID_LOG_DEBUG, "test", "fopen Err!");
  
          return 0;
  
      }
  
  
  
      fseek(srcFile, 0, SEEK_END);
  
      DCFSize = ftell(srcFile);
  
      fseek(srcFile, 0, SEEK_SET);
  
  
  
      int nAudioStreamIdx = -1;
  
      AVCodec *pAudioCodec = NULL;
  
  
  
      err = av_find_stream_info(pInputFormatContext);
  
      if (err < 0) {
  
          __android_log_print(ANDROID_LOG_DEBUG, "test",
  
                  "av_find_stream_info Err!");
  
          __android_log_print(ANDROID_LOG_DEBUG, "test",
  
                  "av_find_stream_info Err!");
  
          return 0;
  
      }
  
  
  
      err = av_find_best_stream(pInputFormatContext, AVMEDIA_TYPE_AUDIO, -1, -1,
  
              &pAudioCodec, NULL);
  
  
  
      //에러처리 임시
  
      if (err < 0) {
  
          nAudioStreamIdx = 1;
  
          if (err == AVERROR_STREAM_NOT_FOUND)
  
              __android_log_print(ANDROID_LOG_DEBUG, "test",
  
                      "AVERROR_STREAM_NOT_FOUND");
  
          if (err == AVERROR_DECODER_NOT_FOUND)
  
              __android_log_print(ANDROID_LOG_DEBUG, "test",
  
                      "AVERROR_DECODER_NOT_FOUND ");
  
      } else
  
          nAudioStreamIdx = err;
  
  
  
      AVPacket Packet;
  
      av_init_packet(&Packet);
  
  
  
      while (av_read_frame(pInputFormatContext, &Packet) >= 0) {
  
          if (Packet.stream_index == nAudioStreamIdx)
  
              {
  
              fwrite(Packet.data, 1, Packet.size, destFile);
  
              PaketPos = Packet.pos;
  
              //__android_log_print(ANDROID_LOG_DEBUG, "test","Extract Progress : %d",getExtractProgress());
  
          }
  
      }
  
      PaketPos = DCFSize;
  
  
  
      return 1;
  
  }