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• file protocol : handle the file : protocol string in file_check

  13 octobre 2016, par Anton Khirnov

  file protocol : handle the file : protocol string in file_check
  This is consistent with what file_open() does.
  CC : libav-stable@libav.org
  

  • [DBH] libavformat/file.c

• Can I programmatically insert audio from a Webm file into another Webm file ?

  18 janvier 2016, par andy

  I have two WebM files, both have video and audio.

  I want to insert the audio from one WebM file into the other so that the final WebM file has two audio "streams" playing simultaneously with the video.

  Is it possible to achieve this programatically ? Preferably with Ruby, or if not with a command line interface, maybe ffmpeg ?

• store pcm data into file, but can not play that file

  25 mai 2016, par Peng Qu

  I am writing a simple program, which reads mp3 file and store its pcm data into another file. I could get that file now, but when I play that on windows, I failed. So is there any wrong in my code, or windows couldn’t play raw audio data ?

  #include 
  
  #include 
  
  #include <libavutil></libavutil>avutil.h>
  
  #include <libavformat></libavformat>avformat.h>
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  
  
  int main()
  
  {
  
  int err;
  
  FILE *fout = fopen("test.wav", "wb");
  
  av_register_all();
  
  
  
  // step 1, open file and find audio stream
  
  AVFormatContext *fmtx = NULL;
  
  err = avformat_open_input(&amp;fmtx, "melodylove.mp3", NULL, NULL);
  
  assert(!err);
  
  
  
  err = avformat_find_stream_info(fmtx, NULL);
  
  assert(!err);
  
  
  
  int audio_stream_idx = -1;
  
  AVStream *st;
  
  AVCodecContext *decx;
  
  AVCodec *dec;
  
  
  
  for (int i = 0; i &lt; fmtx->nb_streams; ++i) {
  
      audio_stream_idx = i;
  
      if (fmtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO) {
  
          st = fmtx->streams[i];
  
          decx = st->codec;
  
          dec = avcodec_find_decoder(decx->codec_id);
  
          decx->request_channel_layout = AV_CH_LAYOUT_STEREO_DOWNMIX;
  
          decx->request_sample_fmt = AV_SAMPLE_FMT_FLT;
  
          avcodec_open2(decx, dec, NULL);
  
          break;
  
      }
  
  }
  
  assert(audio_stream_idx != -1);
  
  
  
  int channels = decx->channels;
  
  int sample_rate = decx->sample_rate;
  
  int planar = av_sample_fmt_is_planar(decx->sample_fmt);
  
  int num_planes =  planar? decx->channels : 1;
  
  const char *sample_name = av_get_sample_fmt_name(decx->sample_fmt);
  
  printf("sample name: %s, channels: %d, sample rate: %d\n",
  
          sample_name, channels, sample_rate);
  
  printf("is planar: %d, planes: %d\n", planar, num_planes);
  
  
  
  /*
  
   * above I print some infomation about mp3 file, they are:
  
   * sample name: s16p, channels: 2, sample rate: 48000
  
   * is planar: 1, planes: 2
  
   */
  
  getchar();
  
  
  
  AVPacket pkt;
  
  av_init_packet(&amp;pkt);
  
  AVFrame *frame = av_frame_alloc();
  
  
  
  while (1) {
  
      err = av_read_frame(fmtx, &amp;pkt);
  
      if (err &lt; 0) {
  
          printf("read frame fail\n");
  
          fclose(fout);
  
          exit(-1);
  
      }
  
      if (pkt.stream_index != audio_stream_idx) {
  
          printf("we don't need this stream\n");
  
          continue;
  
      }
  
      printf("data size: %d\n", pkt.size);
  
  
  
      int got_frame = 0;
  
      int bytes = avcodec_decode_audio4(decx, frame, &amp;got_frame, &amp;pkt);
  
      if (bytes &lt; 0) {
  
          printf("decode audio fail\n");
  
          continue;
  
      }
  
      printf("frame size: %d, samples: %d\n", bytes, frame->nb_samples);
  
  
  
      if (got_frame) {
  
          int input_samples = frame->nb_samples * decx->channels;
  
          int sz = input_samples / num_planes;
  
          short buffer1[input_samples];
  
  
  
          for (int j = 0; j &lt; frame->nb_samples; ++j) {
  
              for (int i = 0; i &lt; num_planes; ++i) {
  
                  short *d = (short *)frame->data[i];
  
                  buffer1[j*2+i] = d[j];
  
              }
  
          }
  
  
  
          fwrite(buffer1, input_samples, 2, fout);
  
      } else {
  
          printf("why not get frame???");
  
      }
  
  }
  
  }