Recherche avancée

Sur d’autres sites (10344)

• h264 : do not return on sidedata allocation failure

  22 août 2014, par Christophe Gisquet

  h264 : do not return on sidedata allocation failure
  Not having allocated it is not a good reason to leave the object
  
  in an undetermined state. Though a particular setting like the
  
  AV_EF_* flags could be useful to control that behaviour.
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavcodec/h264.c

• metadata_object.c : Remove un-needed asserts

  10 juillet 2016, par Erik de Castro Lopo

  metadata_object.c : Remove un-needed asserts
  These asserts were being triggered by AFL (American Fuzzy Lop) and
  
  serve seemingly no useful purpose. The are only enabled in debug builds
  
  where they abort the program which is otherwise in a safe state.
  Removing these asserts will potentially allow AFL to turn up other
  
  problems elsewhere.
  

  • [DH] src/libFLAC/metadata_object.c

• Streaming Audio with OpenAL and FFMPEG

  28 janvier 2013, par Michael Barth

  Alright, basically I'm working on a simple video player and I'll probably be asking another question about lagging video\syncing to audio later, but for now I'm having a problem with audio. What I've managed to do to is go through all of the audio frames of a video and add them to a vector buffer then play the audio from that buffer using OpenAL.

  This is inefficient and memory hogging and so I need to be able stream it using what I guess is called a rotating buffer. I've ran into problems, one being that there's not a lot of information on streaming with OpenAL let alone the proper way to decode audio with FFMPEG and pipe it to OpenAL. I'm even less comfortable using a vector for my buffer because I honestly have no idea how vectors work in C++, but I some how managed to pull something out of my head to make it work.

  Currently I have a Video class that looks like this :

  class Video
  
  {
  
      public:
  
          Video(string MOV);
  
          ~Video();
  
          bool HasError();
  
          string GetError();
  
          void UpdateVideo();
  
          void RenderToQuad(float Width, float Height);
  
          void CleanTexture();
  
      private:
  
          string FileName;
  
          bool Error;
  
          int videoStream, audioStream, FrameFinished, ErrorLevel;
  
          AVPacket packet;
  
          AVFormatContext *pFormatCtx;
  
          AVCodecContext *pCodecCtx, *aCodecCtx;
  
          AVCodec *pCodec, *aCodec;
  
          AVFrame *pFrame, *pFrameRGB, *aFrame;
  
  
  
          GLuint VideoTexture;
  
          struct SwsContext* swsContext;
  
  
  
          ALint state;
  
          ALuint bufferID, sourceID;
  
          ALenum format;
  
          ALsizei freq;
  
  
  
          vector  bufferData;
  
  };

  The bottom private variables are the relevant ones. Currently I'm decoding audio in the class constructor to an AVFrame and adding the data to bufferData like so :

      av_init_packet(&packet);
  
  
  
      alGenBuffers(1, &bufferID);
  
      alGenSources(1, &sourceID);
  
  
  
      alListener3f(AL_POSITION, 0.0f, 0.0f, 0.0f);
  
  
  
      int GotFrame = 0;
  
  
  
      freq = aCodecCtx->sample_rate;
  
      if (aCodecCtx->channels == 1)
  
          format = AL_FORMAT_MONO16;
  
      else
  
          format = AL_FORMAT_STEREO16;
  
  
  
      while (av_read_frame(pFormatCtx, &packet) >= 0)
  
      {
  
          if (packet.stream_index == audioStream)
  
          {
  
              avcodec_decode_audio4(aCodecCtx, aFrame, &GotFrame, &packet);
  
              bufferData.insert(bufferData.end(), aFrame->data[0], aFrame->data[0] + aFrame->linesize[0]);
  
              av_free_packet(&packet);
  
          }
  
      }
  
      av_seek_frame(pFormatCtx, audioStream, 0, AVSEEK_FLAG_BACKWARD);
  
  
  
      alBufferData(bufferID, format, &amp;bufferData[0], static_cast<alsizei>(bufferData.size()), freq);
  
  
  
      alSourcei(sourceID, AL_BUFFER, bufferID);
  
  </alsizei>

  In my UpdateVideo() is where I'm decoding video to an OpenGL texture through the video stream, so it would make sense for me to decode my audio there and stream it :

  void Video::UpdateVideo()
  
  {
  
      alGetSourcei(sourceID, AL_SOURCE_STATE, &state);
  
      if (state != AL_PLAYING)
  
          alSourcePlay(sourceID);
  
      if (av_read_frame(pFormatCtx, &packet) >= 0)
  
      {
  
          if (packet.stream_index == videoStream)
  
          {
  
              avcodec_decode_video2(pCodecCtx, pFrame, &FrameFinished, &packet);
  
              if (FrameFinished)
  
              {
  
                  sws_scale(swsContext, pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize);
  
                  av_free_packet(&packet);
  
              }
  
          }
  
          else if (packet.stream_index == audioStream)
  
          {
  
              /*
  
              avcodec_decode_audio4(aCodecCtx, aFrame, &FrameFinishd, &packet);
  
              if (FrameFinished)
  
              {
  
                  //Update Audio and rotate buffers here!
  
              }
  
              */
  
          }
  
          glGenTextures(1, &VideoTexture);
  
          glBindTexture(GL_TEXTURE_2D, VideoTexture);
  
          glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  
          glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  
          glTexImage2D(GL_TEXTURE_2D, 0, 3, pCodecCtx->width, pCodecCtx->height, 0, GL_RGB, GL_UNSIGNED_BYTE, pFrameRGB->data[0]);
  
      }
  
      else
  
      {
  
          av_seek_frame(pFormatCtx, videoStream, 0, AVSEEK_FLAG_BACKWARD);
  
      }
  
  }

  So I guess the big question is how do I do it ? I've got no clue. Any help is appreciated, thank you !