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• How to estimate bandwidth / speed requirements for real-time streaming video ?

  19 juin 2016, par Vivek Seth

  For a project I’m working on, I’m trying to stream video to an iPhone through its headphone jack. My estimated bitrate is about 200kbps (If i’m wrong about this, please ignore that).

  I’d like to squeeze as much performance out of this bitrate as possible and sound is not important for me, only video. My understanding is that to stream a a real-time video I will need to encode it with some codec on-the-fly and send compressed frames to the iPhone for it to decode and render. Based on my research, it seems that H.265 is one of the most space efficient codecs available so i’m considering using that.

  Assuming my basic understanding of live streaming is correct, how would I estimate the FPS I could achieve for a given resolution using the H.265 codec ?

  The best solution I can think of it to take a video file, encode it with H.265 and trim it to 1 minute of length to see how large the file is. The issue I see with this approach is that I think my calculations would include some overhead from the video container format (AVI, MKV, etc) and from the audio channels that I don’t care about.

• OpenCV [[mjpeg @ 0000000000428480] overread 8] during reading a frame from camera

  8 octobre 2015, par wojcienty

  I have a very annoying OpenCV error, that i can’t understand, and handle with.
  I write an application which gets mjpg’s stream from ip camera, and process it, but when i try to load image from stream, sometimes i have

  [mjpeg @ 0000000000428480] overread 8

  error, and i don’t know why.
  Even if i try to skip this issue, and try to load next frame from the stream, the application stucks on

  frameStatus = cameraHandler->read(mat);

  This is code for connection establishing :

  void ImageProcessor::connectWithCamera(VideoCapture * cameraHandler) {
  
      if (cameraHandler != nullptr) {
  
          Logger::log("Closing existing camera stream.");
  
          cameraHandler->release();
  
          delete cameraHandler;
  
      }
  
      Logger::log("Camera configuration and connection establishing.");
  
      cameraHandler = new VideoCapture();
  
      cameraHandler->set(CV_CAP_PROP_FRAME_WIDTH, config.RESOLUTION_WIDTH);
  
      cameraHandler->set(CV_CAP_PROP_FRAME_HEIGHT, config.RESOLUTION_HEIGHT);
  
      cameraHandler->set(CV_CAP_PROP_FPS, config.CAMERA_FPS);
  
      cameraHandler->set(CV_CAP_PROP_FOURCC, CV_FOURCC('M', 'J', 'P', 'G'));
  
      while (!cameraHandler->open(config.LINK)) {
  
          Logger::log("Cannot connect to camera! Trying again.");
  
      }
  
  }

  And this is code for capturing images :

  void ImageProcessor::start() {
  
  
  
      VideoCapture * cameraHandler = new VideoCapture();
  
      this->connectWithCamera(cameraHandler);
  
      this->connectWithServer(this->serverConnection);
  
  
  
      Logger::log("Id sending.");
  
      serverConnection->send(config.TOKEN + "\n");
  
      Logger::log("Computations starting.");
  
  
  
      Mat mat;
  
      Result * result = nullptr;
  
      int delta = 1000 / cameraHandler->get(CV_CAP_PROP_FPS);
  
      char frameErrorCounter = 0;
  
      bool frameStatus;
  
  
  
      while (true) {
  
          frameStatus = false;
  
          cv::waitKey(delta);
  
  
  
          try {
  
              frameStatus = cameraHandler->read(mat);
  
          } catch (std::exception& e) {
  
              std::string message = e.what();
  
              Logger::log("Critical camera error! : " + message);
  
          }
  
  
  
          if (!frameStatus) {
  
              Logger::log("Cannot read a frame from source. ");
  
              ++frameErrorCounter;
  
              if (!cameraHandler->isOpened() || frameErrorCounter >= this->GET_FRAME_ERROR_COUNTER) {
  
                  Logger::log("Probably camera is disconnected. Trying to establish connection again.");
  
                  frameErrorCounter = 0;
  
                  this->connectWithCamera(cameraHandler);
  
                  Logger::log("Computations starting.");
  
              }
  
              continue;
  
          }
  
  
  
          result = processImage(mat);
  
  
  
          std::string stringResult;
  
          if (result == nullptr) {
  
              stringResult = this->NO_RESULT;
  
              delete result;
  
              result = nullptr;
  
          } else {
  
              stringResult = result->toJson();
  
          }
  
  
  
          if (!serverConnection->send(stringResult)) {
  
              Logger::log("Server connection lost, trying to establish it again.");
  
              serverConnection->close();
  
              while (!serverConnection->isOpen()) {
  
                  this->connectWithServer(serverConnection);
  
              }
  
          }
  
  
  
          mat.release();
  
      }
  
  
  
  }

  Thanks in advance !

• mmal : Remove setting extradata on input format

  24 septembre 2015, par wm4

  mmal : Remove setting extradata on input format
  This works only for extradata sizes up to 128 bytes. Additionally, I
  
  could never actually see it doing anything. The new code using
  
  MMAL_BUFFER_HEADER_FLAG_CONFIG now takes care of this.
  Signed-off-by : Luca Barbato <lu_zero@gentoo.org>
  

  • [DBH] libavcodec/mmaldec.c