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• conversion from cv::mat to avframe, encode in h264 dont writing correctly [on hold]

  15 novembre 2014, par danics

  i create a method for converting between cv::mat to avframe with PIX_FMT_YUV420P format (oframe format) but _convCtx always return null, whats wrong ? thanks in advance ! ((i solve this)) but i have another probelm in end of this question please

  void processToFrame(cv::Mat* _mat, AVFrame* oframe)
  
    {
  
        // Create and allocate the conversion frame.
  
        if (_oframe == nullptr) {
  
            _oframe = avcodec_alloc_frame();  
  
            if (_oframe == nullptr)
  
                throw std::runtime_error("Matrix Converter: Could not allocate the output frame.");
  
  
  
            avpicture_alloc(reinterpret_cast(_oframe), 
  
                PIX_FMT_BGR24, _mat->cols, _mat->rows);             
  
        }
  
  
  
        avpicture_fill(reinterpret_cast(_oframe),
  
            (uint8_t *)_mat->data,
  
            AV_PIX_FMT_BGR24,
  
            _mat->cols,
  
            _mat->rows);
  
  
  
        // Convert the image from its native format to BGR.
  
        if (_convCtx == nullptr) {
  
            _convCtx = sws_getContext(
  
                oframe->width, oframe->height, (enum AVPixelFormat) oframe->format, 
  
                _oframe->width, _oframe->height, PIX_FMT_BGR24, 
  
                SWS_BICUBIC, nullptr, nullptr, nullptr);
  
        }
  
        if (_convCtx == nullptr)
  
            throw std::runtime_error("Matrix Converter: Unable to initialize the conversion context.");   
  
  
  
        // Scales the source data according to our SwsContext settings.
  
        if (sws_scale(_convCtx,
  
            _oframe->data, _oframe->linesize, 0, _oframe->height,
  
            oframe->data, oframe->linesize) < 0)
  
            throw std::runtime_error("Matrix Converter: Pixel format conversion not supported.");
  
    }

  create oframe

  void createVideoFile(const char* filename, int w, int h, int codec_id, int fps)
  
    {
  
        /* find the mpeg1 video encoder */
  
        if(codec == nullptr) 
  
        {
  
            /* find the mpeg1 video encoder */
  
            codec = avcodec_find_encoder((AVCodecID)codec_id);
  
            if (!codec) {
  
                throw std::runtime_error("codec not found\n");
  
            }
  
        }
  
  
  
        if(c == nullptr)
  
        {
  
            c = avcodec_alloc_context3(codec);
  
            if(!c)
  
            {
  
                throw std::runtime_error("Could not allocate video codec context\n");
  
            }
  
            /* put sample parameters */
  
            c->bit_rate = 400000;
  
            /* resolution must be a multiple of two */
  
            c->width = 2 * (w / 2);
  
            c->height = 2 * (h / 2);
  
            /* frames per second */
  
            AVRational ar;
  
            ar.den = 1;
  
            ar.num = fps;
  
  
  
            c->time_base= ar; //(AVRational){1,25};
  
            c->gop_size = 10; /* emit one intra frame every ten frames */
  
            c->max_b_frames=1;
  
            c->pix_fmt = PIX_FMT_YUV420P;
  
  
  
            if(codec_id == AV_CODEC_ID_H264)
  
                av_opt_set(c->priv_data, "preset", "slow", 0);
  
  
  
            /* open it */
  
            if (avcodec_open2(c, codec, NULL) < 0) {
  
                throw std::runtime_error("Could not open codec\n");
  
            }
  
  
  
            f = fopen(filename, "wb");
  
            if (!f) {
  
                throw std::runtime_error("could not open file\n");
  
            }
  
  
  
            frame = avcodec_alloc_frame();
  
            if (!frame) {
  
                throw std::runtime_error("Could not allocate video frame\n");
  
            }
  
            frame->format = c->pix_fmt;
  
            frame->width  = c->width;
  
            frame->height = c->height;
  
  
  
            /* the image can be allocated by any means and av_image_alloc() is
  
             * just the most convenient way if av_malloc() is to be used */
  
  
  
            int ret = av_image_alloc(frame->data, frame->linesize, c->width, c->height, c->pix_fmt, 32);
  
  
  
            if (ret < 0) {
  
                throw std::runtime_error("Could not allocate raw picture buffer\n");
  
            }
  
        }
  
  }

  read mat images

  void video_encode_example(const cv::Mat& fin)
  
  {
  
      AVPacket pkt;
  
      /* encode 1 second of video */
  
      av_init_packet(&pkt);
  
      pkt.data = NULL;    // packet data will be allocated by the encoder
  
      pkt.size = 0;
  
  
  
      fflush(stdout);
  
  
  
      cv::Mat res;
  
      cv::resize(fin, res, cv::Size(c->width, c->height));
  
  
  
      processToFrame(&res, frame);
  
      frame->pts = i;
  
  
  
      /* encode the image */
  
      int ret = avcodec_encode_video2(c, &pkt, frame, &got_output);
  
      if (ret < 0) {
  
      throw std::runtime_error("Error encoding frame\n");
  
      }
  
  
  
      if (got_output) {
  
          printf("Write frame %3d (size=%5d)\n", i, pkt.size);
  
          fwrite(pkt.data, 1, pkt.size, f);
  
          av_free_packet(&pkt);
  
      }
  
      i++;
  
  }

  update :

  i can solve the conversion problem by setting of _oframe.width = _mat.cols and _oframe.height = _mat.rows, avpicture_alloc dont set this value itself.

  now i have the other problem my videowriting class seems write ok because windows slideshow show one of frames, but i cant view video in my players, this is my release function, i dont know whats wrong endcoding or endcoder structure parameter like pts and else.

  void video_release()
  
      {
  
          /* get the delayed frames */
  
          for (got_output = 1; got_output; i++) {
  
              fflush(stdout);
  
  
  
              int ret = avcodec_encode_video2(c, &pkt, NULL, &got_output);
  
              if (ret < 0) {
  
                  throw std::runtime_error("Error encoding frame\n");
  
              }
  
  
  
              if (got_output) {
  
                  printf("Write frame %3d (size=%5d)\n", i, pkt.size);
  
                  fwrite(pkt.data, 1, pkt.size, f);
  
                  av_free_packet(&pkt);
  
              }
  
          }
  
  
  
          uint8_t endcode[] = { 0, 0, 1, 0xb7 };
  
  
  
          /* add sequence end code to have a real mpeg file */
  
          fwrite(endcode, 1, sizeof(endcode), f);
  
          fclose(f);
  
  
  
          avcodec_close(c);
  
          av_free(c);
  
          av_freep(&frame->data[0]);
  
          avcodec_free_frame(&frame);
  
  
  
          c = nullptr;
  
          codec = nullptr;
  
          frame = nullptr;
  
  
  
          if (_convCtx)
  
              sws_freeContext(_convCtx);
  
  
  
          if (_oframe) {
  
              //if (_oframe->data)
  
                  //av_free(_oframe->data[0]);
  
              av_free(_oframe);
  
          }
  
  
  
          _oframe = nullptr;
  
          _convCtx = nullptr;
  
      }

• org.bytedeco.javacv.CanvasFrame showImage is hanging

  24 août 2018, par user3911119

  An IOS device is uploading h264 files (3 sec videos) to a server. Each file is successfully readable by VLC.

  Using FFMpegFrameGrabber, I grab each frame and try to display them using CanvasFrame.showImage as below. However, the method call hangs.

  CanvasFrame canvas = new CanvasFrame("ios");
  
  canvas.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  
  canvas.setAlwaysOnTop(true);
  
  canvas.setResizable(true);
  
  try(FileInputStream fis = new FileInputStream(file))
  
  {
  
      try(FFmpegFrameGrabber grabber = new FFmpegFrameGrabber(fis))
  
      {
  
          grabber.setFormat("h264");
  
          grabber.start();
  
          while(true)
  
          {
  
              Frame frame = grabber.grabImage();
  
              if(frame != null)
  
              {
  
                  canvas.showImage(frame);
  
              }
  
          }
  
      }
  
  }

  Am I doing anything wrong in the above code ?

  EDIT#1 : When I try to save the buffered image for the frame, a valid image is saved.

  BufferedImage image = converter.getBufferedImage(frame);
  
  File outputfile = new File("png_file");
  
  ImageIO.write(image, "png", outputfile);

• Streaming android to windows

  13 juin 2017, par iYehuda

  I’m writing an app that enables controlling android devices from windows machines.
  Major part of controlling the device is viewing it’s screen. Currently, my android app (Java code) captures the screen on a fixed rate, compresses it (JPEG) and sends it, while the windows side (C# code) receives buffers of data, each for frame, decompresses them and displays the last decompressed frame.

  Two issues came up from this solution :

  1. Compression of a single image takes 0.3 seconds, which limits me to low FPS streaming with single thread for compressing. I made a thread pool for compressing captured frames, and it damages the app performance.

  2. The compression is not optimal. The screen can be idle for a while and a continuous transmission of the same frame would be done. Usage of streaming/encoding format would be handful and can ease the network traffic.

  I searched for encoding APIs such as MediaCodec and third party libraries such as ffmpeg. All those libraries encode videos and write them to files (maybe I misunderstood them ?).

  What API can I use for streaming my screen and follow these requirements :

  • Fast encoding / non blocking API
  • Outputs raw binary data for each frame. The data must be sent immediately
  • Can be embedded into my existing applicative protocol (protocol buffers based)
  • Available on C# (Windows) and Java or C++ (Android)