Recherche avancée

Sur d’autres sites (6937)

• Reading h264 or h265 stream with ffmpeg/OpenCV : Which is faster ?

  25 novembre 2020, par suckss

  I'm using OpenCV with ffmpeg support to read a RTSP stream coming from an IP camera and then to write the frames to a video. The problem is that the frame size is 2816x2816 at 20 fps i.e. there's a lot of data coming in.

  


  I noticed that there was a significant delay in the stream, so I set the buffer size of the cv::VideoCapture object to 1, because I thought that the frames might just get stuck in the buffer instead of being grabbed and processed. This however just caused for frames to be dropped instead.

  


  My next move was to experiment a bit with the frame size/fps and the encoding of the video that I'm writing. All of those things helped to improve the situation, but in the long run I still have to use a frame size of 2816x2816 and support up to 20 fps, so I can't set it lower sadly.

  


  That's where my question comes in : given the fact that the camera stream is going to be either h264 or h265, which one would be read faster by the cv::VideoCapture object ? And how should I encode the video I'm writing in order to minimize the time spent decoding/encoding frames ?

  


  That's the code I'm using for reference :

  


  using namespace cv;
int main(int argc, char** argv)
{
    VideoCapture cap;
    cap.set(CAP_PROP_BUFFERSIZE, 1); // internal buffer will now store only 1 frames

    if (!cap.open("rtsp://admin:admin@1.1.1.1:554/stream")) {
        return -1;
    }
    VideoWriter videoWr;
    Mat frame;
    cap >> frame;
    //int x264 = cv::VideoWriter::fourcc('x', '2', '6', '4'); //I was trying different options
    int x264 = cv::VideoWriter::fourcc('M', 'J', 'P', 'G');
    videoWr = cv::VideoWriter("test_video.avi", 0, 0, 20, frame.size(), true);

    namedWindow("test", WINDOW_NORMAL);
    cv::resizeWindow("test", 1024, 768);
    
    for (;;)
    {
        cap >> frame;
        if (frame.empty()) break; // end of video stream
        
        imshow("test", frame);
        if (waitKey(10) == 27) break; 
        videoWr << frame;
        
    }

    return 0;
}


  


• Reading JPEG in ffmpeg

  16 juillet 2021, par Paul Lammertsma

  I'm trying to get ffmpeg to encode several individual JPEG images into a video on Android. I've successfully built it for Android (see the configuration string at the end of this post).

  



  I can encode an h.263+ video with randomly generated frame content, and ffmpeg otherwise appears to work well.

  



  A similar question suggests that the following code should be sufficient to load an image into an AvFrame :

  



  // Make sure we have the codecs
av_register_all();

AVFormatContext *pFormatCtx;
int ret = av_open_input_file(&pFormatCtx, imageFileName, NULL, 0, NULL);

if (ret != 0) {
    printf("Can't open image file '%s': code %d, %s",
        imageFileName, ret, strerror(AVERROR(ret)));
}


  



  The above returns the correct absolute file path and error :

  



  


  Failed '/sdcard/DCIM/Camera/IMG083.jpg' : code -1094995529, Unknown error : 1094995529

  


  



  Incidentally, if I omit av_register_all(), it returns with error 2.

  



  I've compiled ffmpeg with the following arguments :

  



  


  


  ./configure —target-os=linux 
 —prefix=$PREFIX 
 —enable-cross-compile 
 —extra-libs="-lgcc" 
 —arch=arm 
 —cc=$PREBUILT/bin/arm-linux-androideabi-gcc 
 —cross-prefix=$PREBUILT/bin/arm-linux-androideabi- 
 —nm=$PREBUILT/bin/arm-linux-androideabi-nm 
 —sysroot=$PLATFORM 
 —extra-cflags=" -O3 -fpic -DANDROID -DHAVE_SYS_UIO_H=1 -Dipv6mr_interface=ipv6mr_ifindex -fasm -Wno-psabi -fno-short-enums -fno-strict-aliasing -finline-limit=300 $OPTIMIZE_CFLAGS " 
 —enable-shared 
 —enable-static 
 —extra-ldflags="-Wl,-rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib -nostdlib -lc -lm -ldl -llog" 
 —disable-everything 
 —enable-demuxer=mov 
 —enable-demuxer=h264 
 —disable-ffplay 
 —enable-protocol=file 
 —enable-avformat 
 —enable-avcodec 
 —enable-decoder=mjpeg 
 —enable-decoder=png 
 —enable-parser=h264 
 —enable-encoder=h263 
 —enable-encoder=h263p 
 —disable-network 
 —enable-zlib 
 —disable-avfilter 
 —disable-avdevice

  


  


  



  Any suggestions would be most welcome !

  


• Where do I find the Saved Image in Android ?

  29 octobre 2016, par FirstStep

  Excuse me, quick question :

  I have this routine of video stream, where I receive packets, convert them to byte[] ,then to bitmaps, then display them on the screen :

  dsocket.receive(packetReceived); // receive packet
  
  byte[] buff = packetReceived.getData(); // convert packet to byte[]
  
  final Bitmap ReceivedImage = BitmapFactory.decodeByteArray(buff, 0, buff.length); // convert byte[] to bitmap image
  
  
  
  runOnUiThread(new Runnable()
  
  {
  
      @Override
  
      public void run()
  
      {
  
          // this is executed on the main (UI) thread
  
          imageView.setImageBitmap(ReceivedImage);
  
      }
  
  });

  Now, I want to implementing a Recording feature. Suggestions say I need to use FFmpeg (which I have no idea how) but first, I need to prepare a directory of the ordered images to then convert it to a video file. Do do that I will save all the images internally, and I am using this answer to save each image :

  if(RecordVideo && !PauseRecording) {
  
      saveToInternalStorage(ReceivedImage, ImageNumber);
  
      ImageNumber++;
  
  }
  
  else
  
  {
  
      if(!RecordVideo)
  
          ImageNumber = 0;
  
  }
  
  
  
  // ...
  
  
  
  private void saveToInternalStorage(Bitmap bitmapImage, int counter){
  
          ContextWrapper cw = new ContextWrapper(getApplicationContext());
  
  
  
          // path to /data/data/yourapp/app_data/imageDir
  
          File MyDirectory = cw.getDir("imageDir", Context.MODE_PRIVATE);
  
  
  
          // Create imageDir
  
          File MyPath = new File(MyDirectory,"Image" + counter + ".jpg");
  
  
  
          FileOutputStream fos = null;
  
          try {
  
              fos = new FileOutputStream(MyPath);
  
  
  
              // Use the compress method on the BitMap object to write image to the OutputStream
  
              bitmapImage.compress(Bitmap.CompressFormat.PNG, 100, fos);
  
  
  
          } catch (Exception e) {
  
              e.printStackTrace();
  
          } finally {
  
              try {
  
                  fos.close();
  
              } catch (IOException e) {
  
                  e.printStackTrace();
  
              }
  
          }
  
          //return MyDirectory.getAbsolutePath();
  
      }

  But I can’t seem to find the directory on my device (To actually see if I succeeded in creating the directory) Where is // path to /data/data/yourapp/app_data/imageDir located exactly ?