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• How to decode audiostream to play with AudioUnits ?

  4 décembre 2015, par sadhi

  I have a PCM ulaw stream that I receive and I want to play this on iOS. To play audio in my app I made an AudioUnit implementation, but since it requires linear PCM I must decode it first. For this I use ffmpeg with the following code :

          AVCodec *codec = avcodec_find_decoder(AV_CODEC_ID_PCM_MULAW);
  
  
  
          self.audio_codec_context = avcodec_alloc_context3(codec);
  
          self.audio_codec_context->codec_type = AVMEDIA_TYPE_AUDIO;
  
          self.audio_codec_context->sample_fmt = *codec->sample_fmts;
  
          self.audio_codec_context->sample_rate = 48000;
  
          self.audio_codec_context->channels    = 1;
  
          //open codec
  
          int result = avcodec_open2(self.audio_codec_context, codec,NULL);            
  
  
  
          //this should hold the raw data
  
          AVFrame * audioFrm = av_frame_alloc();
  
  
  
          AVPacket pkt;
  
          av_init_packet(&pkt);
  
          pkt.data = (unsigned char*)buf;
  
          pkt.size = ret;
  
          pkt.flags = AV_PKT_FLAG_KEY;
  
  
  
          int got_packet;
  
          result = avcodec_decode_audio4(self.audio_codec_context, audioFrm, &got_packet, &pkt);
  
  
  
          AVPacket encodedPkt;
  
          av_init_packet(&encodedPkt);
  
          encodedPkt.size = 0;
  
          encodedPkt.data = NULL;
  
  
  
          if (audioFrm != NULL) {
  
              self.audio_codec_context = NULL;
  
              AVCodec *codec = avcodec_find_encoder(AV_CODEC_ID_PCM_S16LE);
  
  
  
              self.audio_codec_context = avcodec_alloc_context3(codec);
  
              self.audio_codec_context->codec_type = AVMEDIA_TYPE_AUDIO;
  
              self.audio_codec_context->sample_fmt = *codec->sample_fmts;
  
              self.audio_codec_context->bit_rate = 64000;
  
              self.audio_codec_context->sample_rate = 48000;
  
              self.audio_codec_context->channels    = 1;
  
  
  
  
  
              int result = avcodec_open2(self.audio_codec_context, codec,NULL);
  
              if (result < 0) {
  
                  NSLog(@"avcodec_open2 returned %i", result);
  
              }
  
  
  
  
  
              result = avcodec_encode_audio2(self.audio_codec_context, &encodedPkt, audioFrm, &got_packet);
  
  
  
              if (result < 0) {
  
                  NSLog(@"avcodec_encode_audio2 returned %s", av_err2str (result));
  
                  continue;
  
              }
  
          }

  For some reason no matter what I do the audio that comes out at the end is all noise.
  So my question is : How should I decode my audiostrean to play it with AudioUnits ?

• ffmpeg extract video unable to play

  30 juin 2021, par Khánh Phạm Đình

  I use ffmpeg to stream video and show up the camera's frame to window in the same time according to current code :

  


  file record_video_and_showup.sh

  


  ffmpeg -f v4l2 -framerate 30 -i $1  -c:v libx264 -preset superfast -crf 18 -pix_fmt yuv420p  -c:a libmp3lame -ac 2 -ar 44100 -b:a 128k -f tee  -map 0:v "$2|[f=nut]pipe:" | ffplay -an pipe:


  


  to record video and show up :

  


  ./record_video_and_showup.sh /dev/video0 test.mp4


  


  finally, we get file test.mp4 but can't play it on app such as vlc. When we open it on google chrome, it can run but the start and end time were incorrect.

  


  Can anyone help me ?

  


• How to stream video with Play 2 framework

  28 avril 2015, par davidshen84

  I want to use Play 2 framework to develop a simple video stream function on my website. The videos are in mp4 format.

  I used the Enumerator, and the method discussed at this post. In the client side, I use the <video></video> tag to play my video. I tested my application on 3 latest browsers, but none of them can play my video :

  • Chrome : display a empty player
  • IE : it tries to download the video like a file...i guess it is IE
  • Firefox : display a message saying the video is corrupted

  However, if I download the video file, it can be played in the player. I am not sure whether it is because my video codec does not support streaming, or it’s my code has problem.

  ffmpeg -i input.mp4 :

    built with gcc 4.9.2 (GCC)
  
    configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libdcadec 
  
  --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger 
  
  --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 
  
  --enable-libxavs --enable-libxvid --enable-lzma --enable-decklink --enable-zlib
  
    libavutil      54. 23.101 / 54. 23.101
  
    libavcodec     56. 35.101 / 56. 35.101
  
    libavformat    56. 31.100 / 56. 31.100
  
    libavdevice    56.  4.100 / 56.  4.100
  
    libavfilter     5. 14.100 /  5. 14.100
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  1.100 /  1.  1.100
  
    libpostproc    53.  3.100 / 53.  3.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '.\input.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 
  
  512
  
      compatible_brands: 
  
  isomiso2mp41
  
      encoder         : Lavf56.31.10
  
  0
  
    Duration: 
  
  00:00:14.4
  
  0
  
  , start: 
  
  0.000000
  
  , bitrate:
  
   890 kb/s
  
      Stream #0:
  
  0(und): Video: mpeg4 (mp4v / 0x7634706D), yuv420p, 160x120 [SAR 1:1 DAR 4:3], 889 kb/s, 
  
  25 fps, 
  
  25 tbr, 
  
  12800 tbn,
  
   30k tbc
  
   (default)
  
      Metadata:
  
        handler_name    : 
  
  VideoHandler
  
  At least one output file must be specified