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• Merge commit ’99434f4df81b6801b2b535d5b9143305595784f6’

  30 mars 2017, par Clément Bœsch

  Merge commit ’99434f4df81b6801b2b535d5b9143305595784f6’
  * commit ’99434f4df81b6801b2b535d5b9143305595784f6’ :
  
    float_dsp : Have implementation match function pointer prototype
  Merged-by : Clément Bœsch <cboesch@gopro.com>
  

  • [DH] libavutil/x86/float_dsp_init.c

• Streaming webcam from ffmpeg to Electron app

  28 mars 2017, par potatoes

  I’m working on a prototype application that consists of an Electron app that talks to a local Flask-based Python service (both on the same machine). On the electron app I want to have a "start" button that has starts to record the machine’s desktop (screencast). I do this by using ffmpeg at the Python backend. In a python subprocess I issue the following command :

  ffmpeg -f gdigrab -framerate 30 -i desktop `outputFile`

  Similarly, I’m able to record the webcam with ffmpeg as follows :

  ffmpeg -f dshow -i video="Integrated Webcam" `outputFile`

  However, I want to be able to stream the webcam to the electron app while recording simultaneously. This is to show a "screencasting" experience at the electron end. So basically my question boils down to streaming to an html5 video element while simultaneously recroding it in ffmpeg. I’ve searched for a way to do so and this page suggest that I can do it over a VLC streaming server locally ? I found a few links but I’m not sure whether I should be starting some kind of RTP server locally and streaming the webcam from ffmpeg to that server which will distribute the stream ? I’m confused about what is needed to make this happen, and any pointers are appretiated ! Thanks !

• Out-of-range channels being referenced when decoding AAC AUs

  3 février 2017, par SoxInCincy

  As part of a proprietary data stream, I have variable length AUs of raw AAC encoded data. The data is single channel and I have the configuration information on how the data was encoded. I need to decode this data to PCM for playback. Right now, I am trying to do so using ffmpeg’s libavcodec, but to no avail. The error I get from ffmpeg(libavcodec) when trying to decode is "channel element 3.7 is not allocated." As I am trying to decode single channel data, have the context set as single channel and channel layout of mono, I am not entirely sure why the decoder is looking for channels beyond 1.

  Can anyone point me in the right direction ? I appreciate any help !

  Prototype Code :

  //Initialize the decoder before sending AUs
  
  bool AAC_Decoder::initialize()
  
  {
  
      //register codecs
  
      avcodec_register_all();
  
      c=NULL;
  
      //attempt to find AAC decoder
  
      codec = avcodec_find_decoder(AV_CODEC_ID_AAC);
  
      if (codec==NULL)
  
      {
  
          std::cout<<"Could Not Find Codec"</setup codec context using known information about the stream
  
      c=avcodec_alloc_context3(codec);
  
      c->bit_rate=32000;
  
      c->channels=1;
  
      c->channel_layout=AV_CH_LAYOUT_MONO;
  
      c->sample_rate=16000;
  
  
  
      //attempt to open the codec using the prescribed context and no options
  
      if (avcodec_open2(c,codec,NULL)<0)
  
      {
  
          std::cout<<"Could Not Open Codec"</decode a single AU sent in a buffer
  
  bool AAC_Decoder::decode(uint8_t *sampleBuffer, uint32_t size)
  
  {
  
      //setup single AU packet
  
      AVPacket avPacket;
  
      av_init_packet(&avPacket);
  
      AVFrame * frame;
  
      pkt.size = size;
  
      pkt.data = sampleBuffer;
  
  
  
      //attempt to setup a frame
  
      frame = av_frame_alloc();
  
      if (!frame)
  
      {
  
          std::cout<<"Could not Allocate Frame"</attempt to decode the frame
  
      int gotFrame =0;
  
      int len = 0;
  
      len = avcodec_decode_audio4(c,frame,&gotFrame,&pkt);
  
  
  
      if (len < 0)//could not decode frame.  Currently getting -22 as response
  
      {
  
          std::cout<<"decoding error"</verify the frame was decoded.  
  
      {
  
          std::cout<<"don't have frame"</successfully decoded.  for now, cout the size as verification.
  
      {
  
          int data_size = av_samples_get_buffer_size(NULL, c->channels, frame->nb_samples, c->sample_fmt, 1);
  
          std::cout</free frame and return
  
      av_frame_free(&frame);
  
      return true;
  
  }