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• swr_convert float planar to S16

  8 janvier 2020, par Kevin Kouketsu

  How convert using libav API AV_SAMPLE_FMT_FLTP to AV_SAMPLE_FMT_S16

  I’m trying to figure out how to resample and encode PCM (captured from Microphone) 44.1KHz to AAC 48.0KHz

  That’s my resampler initializer :

  void initialize_resampler(SwrContext*& resamplerCtx, AVCodecContext* encoder, AVFrame*& rawResampledAudioFrame, AVStream* audioFormatStream)
  
  {
  
      int nb_samples = (encoder->codec->capabilities & AV_CODEC_CAP_VARIABLE_FRAME_SIZE) ? encoder->sample_rate : encoder->frame_size;
  
  
  
      int encoderFrameSize = encoder->channels * av_get_bytes_per_sample(encoder->sample_fmt) * encoder->frame_size;
  
      rawResampledAudioFrame = allocate_audioframe(encoder->sample_fmt, encoder->channel_layout, encoder->sample_rate, nb_samples);
  
  
  
      // Copy the stream parameters to the muxer
  
      check(avcodec_parameters_from_context(audioFormatStream->codecpar, encoder));
  
  
  
      // Create resampler context
  
      resamplerCtx = swr_alloc();
  
      if (resamplerCtx == nullptr)
  
          throw std::runtime_error("Could not allocate resampler context");
  
  
  
      // Set options
  
      check(av_opt_set_int(resamplerCtx, "in_channel_count", 2, 0));
  
      check(av_opt_set_int(resamplerCtx, "in_sample_rate", 44100, 0));
  
      check(av_opt_set_sample_fmt(resamplerCtx, "in_sample_fmt", AV_SAMPLE_FMT_S16, 0));
  
      check(av_opt_set_int(resamplerCtx, "out_channel_count", encoder->channels, 0));
  
      check(av_opt_set_int(resamplerCtx, "out_sample_rate", encoder->sample_rate, 0));
  
      check(av_opt_set_sample_fmt(resamplerCtx, "out_sample_fmt", encoder->sample_fmt, 0));
  
  
  
      // initialize the resampling context
  
      check(swr_init(resamplerCtx));
  
  }

  And for resample I’ve this code :

      AVPacket pkt{};
  
      while (true)
  
      {
  
          AVPacket input_packet;
  
          av_init_packet(&input_packet);
  
  
  
          check(av_read_frame(inputContext, &input_packet));
  
  
  
          check(avcodec_send_packet(decoderContext, &input_packet));
  
          check(avcodec_receive_frame(decoderContext, decodedFrame));
  
  
  
  
  
          // WHAT DO HERE swr_convert(resamplerContext, )
  
          av_packet_unref(&input_packet);
  
  
  
          av_init_packet(&pkt);
  
          auto in_stream = inputContext->streams[pkt.stream_index];
  
          auto out_stream = outputContext->streams[pkt.stream_index];
  
  
  
          pkt.pts = av_rescale_q_rnd(pkt.pts, in_stream->time_base, out_stream->time_base, (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
  
          pkt.dts = av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base, (AVRounding)(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));
  
          pkt.duration = av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);
  
          pkt.pos = -1;
  
  
  
          check(avcodec_send_frame(encoderContext, decodedFrame));
  
          check(avcodec_receive_packet(encoderContext, &pkt));
  
  
  
          check(av_interleaved_write_frame(outputContext, &pkt));
  
          av_packet_unref(&pkt);
  
      }

  REading the docs I can’t figure out what exactly I need to pass to function. I have this code to encode PCM to MP2 (output is AV_SAMPLE_FMT_S16)

  const uint8_t* inPtr[] { const_cast<const>(&amp;pcmData[0]), nullptr, nullptr,nullptr,nullptr,nullptr,nullptr,nullptr };
  
  uint8_t* outPtr[] { &amp;resampledAudioData[0], nullptr, nullptr,nullptr,nullptr,nullptr,nullptr,nullptr };
  
  
  
  int resampledSamplesCount{ swr_convert(
  
      resamplerCtx,
  
      outPtr,
  
      maxResampledSamplesCount,
  
      inPtr,
  
      inputSampleCount) };
  
  
  
  // Negativo indica erro.
  
  check(resampledSamplesCount);
  
  </const>

  pcmData is raw data from input AVPacket (PCM)

  What I get here is : MP2 isn’t planar so it uses the same outPtr[0] different from plannar which needs two valid pointers to same writable data. But what I need to pass to inPtr, for example ?

  When I try to use the same code, ffmpeg try to write on outPtr[1] which is nullptr.

• Grab frame from video (as Inputstream) using JavaCV in Java

  23 janvier 2020, par Praveen Gopal

  I am using JavaCV to grab frame from Video.

  I can grab if video is in absolute path. But if video is in HTTP than JavaCV throw error.

      url = new URL("http://www.sample-videos.com/video/mp4/720/SampleVideo.mp4");
  
      urlConnection = (HttpURLConnection) url.openConnection();
  
      InputStream inputStream = urlConnection.getInputStream();
  
      Java2DFrameConverter bimConverter = new Java2DFrameConverter();
  
  
  
      FFmpegFrameGrabber frameGrabber = new FFmpegFrameGrabber(inputStream);
  
  
  
      String output = "C:\\Users\\xxxx\\Downloads\\Test";
  
      frameGrabber.start();
  
       Frame frame;  
  
       double frameRate=frameGrabber.getFrameRate();  
  
       int imgNum=5;  
  
       System.out.println("Video has "+frameGrabber.getFrameRate()+" frames and has frame rate of "+frameRate);  
  
       try {   
  
         frameGrabber.setFrameNumber(1000);
  
         frame = frameGrabber.grabKeyFrame();  
  
         BufferedImage bi = bimConverter.convert(frame);  
  
         String path = output+File.separator+imgNum+".jpg";  
  
         ImageIO.write(bi,"png", new File(path));
  
         frameGrabber.stop();   
  
         frameGrabber.close();
  
         frameGrabber.flush();                                                                        
  
       } catch (Exception e) {  
  
         e.printStackTrace();  
  
       } 

  Any help would be helpful.
  Thanks in advance.

• Grab frame from video using JavaCV

  26 août 2020, par Praveen Gopal

  I am using JavaCV to grab frame from Video.

  


  I can grab if video is in absolute path. But if video is in HTTP than JavaCV throw error.

  


      url = new URL("http://www.sample-videos.com/video/mp4/720/SampleVideo.mp4");
    urlConnection = (HttpURLConnection) url.openConnection();
    InputStream inputStream = urlConnection.getInputStream();
    Java2DFrameConverter bimConverter = new Java2DFrameConverter();

    FFmpegFrameGrabber frameGrabber = new FFmpegFrameGrabber(inputStream);

    String output = "C:\\Users\\xxxx\\Downloads\\Test";
    frameGrabber.start();
     Frame frame;  
     double frameRate=frameGrabber.getFrameRate();  
     int imgNum=5;  
     System.out.println("Video has "+frameGrabber.getFrameRate()+" frames and has frame rate of "+frameRate);  
     try {   
       frameGrabber.setFrameNumber(1000);
       frame = frameGrabber.grabKeyFrame();  
       BufferedImage bi = bimConverter.convert(frame);  
       String path = output+File.separator+imgNum+".jpg";  
       ImageIO.write(bi,"png", new File(path));
       frameGrabber.stop();   
       frameGrabber.close();
       frameGrabber.flush();                                                                        
     } catch (Exception e) {  
       e.printStackTrace();  
     }