Recherche avancée

Sur d’autres sites (11042)

• Piping PCM data from FFMPEG to another process with Python subprocess

  13 février 2017, par Pete Bleackley

  I am trying to transcribe a podcast. To do so, I am decoding the mp3 stream with FFMPEG, and piping the resulting PCM output to the speech recognition component. My code looks like this.

  mp3=subprocess.Popen(['ffmpeg','-i',audio_url,
  
                                '-f','s16le','-ac','1','-ar','16000','pipe:0'],
  
                                stdout=subprocess.PIPE)
  
  sphinx=subprocess.Popen(['java','-jar','transcriber.jar'],
  
                                  stdin=mp3.stdout,
  
                                  stdout=subprocess.PIPE)

  Where audio_url is the url of the mp3 file.

  When I try to run this, it hangs. It appears that feeding the decoded PCM data through the pipe has deadlocked. What can I do to fix this ? The size of the output data is likely to be too big for subprocess.Popen.communicate to be an option, and explicitly calling mp3.stdout.close() has had no effect.

• Display video data to screen

  23 septembre 2014, par user3215358

  I’m trying to decode h264 video using HW with Stagefright library and render it.

  I want to display data to screen with SDL.

  I’m getting video data to MediaBuffer. For non H/W decoding video displays well by using FFMpeg library. Here is piece of rendering code.

  while (av_read_frame(pFormatCtx, &packet) >= 0) 
  
  {
  
      // Is this a packet from the video stream?
  
      if (packet.stream_index == videoStream) 
  
      {
  
          avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
  
  
  
          if (frameFinished) 
  
          {
  
  
  
              SDL_UpdateYUVTexture(bmp, NULL, pFrame->data[0], 
  
                                              pFrame->linesize[0], 
  
                                              pFrame->data[1], 
  
                                              pFrame->linesize[1], 
  
                                              pFrame->data[2], 
  
                                              pFrame->linesize[2]); 
  
  
  
  
  
              rect.x = 0;
  
              rect.y = 0;
  
              rect.w = pCodecCtx->width;
  
              rect.h = pCodecCtx->height;
  
  
  
              SDL_SetRenderDrawColor(renderer, 0, 80, 0, 255);
  
              SDL_RenderClear(renderer); 
  
              SDL_RenderCopy(renderer, bmp, NULL, &rect); 
  
              SDL_RenderPresent(renderer); 
  
          }
  
      }

  But when i’m using H/W accelerated decoding, what I should use in SDL_UpdateYUVTexture(bmp, NULL,....) function.

  And Here is piece of H/W accelerated decoding.

  while (err != ERROR_END_OF_STREAM )
  
  {
  
  
  
      MediaBuffer *mVideoBuffer;
  
      MediaSource::ReadOptions options;
  
      err = mVideoDecoder->read(&mVideoBuffer, &options);
  
  
  
      if (err == OK) {
  
          if (mVideoBuffer->range_length() > 0) 
  
          {
  
              //SDL_UpdateYUVTexture(bmp, NULL,...); 
  
  
  
              rect.x = 0;
  
              rect.y = 0;
  
              rect.w = 640;
  
              rect.h = 480;
  
  
  
              SDL_SetRenderDrawColor(renderer, 0, 80, 0, 255);
  
              SDL_RenderClear(renderer); 
  
              SDL_RenderCopy(renderer, bmp, NULL, &rect); 
  
              SDL_RenderPresent(renderer); 
  
  
  
          }
  
          mVideoBuffer->release();
  
      }
  
  }

  How i should use SDL_UpdateYUVTexture(bmp, NULL,...) function ?

• How to fill AVFrame with audio data

  12 décembre 2014, par Andy

  I use Win32 API to implement a desktop recording program.
  The video capture feature works, but I have no idea to put the audio in the FFmpeg encoder’s data structure.

  The below code will get the data of the default output audio.

  // Set wave format when sampling the audio
  
  WAVEFORMATEX wf; 
  
  wf->wFormatTag = WAVE_FORMAT_PCM;
  
  wf->nChannels = 1;
  
  wf->nSamplesPerSec = 12000;
  
  wf->nBlockAlign = 1;
  
  wf->wBitsPerSample = 8;
  
  wf->cbSize = 0;
  
  wf->nAvgBytesPerSec = nChannels * nSamplesPerSec * wBitsPerSample / 8;
  
  
  
  // Open wave input channel
  
  HWAVEIN hWaveIn;
  
  OpenWaveIn(&hWaveIn,&wf);
  
  
  
  // Prepare Wave In Header and allocate memory
  
  WAVEHDR waveHdr;
  
  DWORD dataSize = 240000L;
  
   PrepareWaveIn(&hWaveIn, &waveHdr, dataSize);
  
  
  
  // Start recording
  
  StartRecord(&hWaveIn);
  
  
  
  // Stop recording
  
  MMTIME mmt;
  
  StopRecord(&hWaveIn, &mmt);

  waveHdr->lpData is a pointer to locked data buffer.

  The question is how can I implement the below function let the waveHdr->->lpData can be saved to AVFrame ?

  static AVFrame *get_audio_frame(OutputStream *ost)
  
  {
  
      AVFrame *frame = ost->tmp_frame;
  
      int j, i, v;
  
      int16_t *q = (int16_t*)frame->data[0];
  
      AVRational arg;
  
      arg.num = 1;
  
      arg.den = 1;
  
  
  
      //the transform code should be put here
  
  
  
      frame->pts = ost->next_pts;
  
      ost->next_pts += frame->nb_samples;
  
      return frame;
  
  }

  Does someone know how can implement this ?