Recherche avancée

Sur d’autres sites (10257)

• Read h264 stream from an IP camera

  13 juillet 2015, par João Neves

  Currently, I am trying to use opencv to read a video from my Canon VB-H710F camera.

  For this purpose I tried two different solutions :

  SOLUTION 1 : Read the stream from rtsp address

   VideoCapture cam ("rtsp://root:camera@10.0.4.127/stream/profile1=u");
  
  
  
   while(true)
  
    cam >> frame;

  In this case I am using opencv to directly read from a stream encoded with in H264 (profile1), however this yields the same problem reported here http://answers.opencv.org/question/34012/ip-camera-h264-error-while-decoding/
  As suggested in the previous question, I tried to disable FFMPEG support in opencv installation, which solved the h264 decoding errors but raised other problem.
  When accessing the stream with opencv, supported by gstreame, there is always a large delay associated.
  With this solution I achieve 15 FPS but I have a delay of 5 seconds, which is not acceptable considering that I need a real time application.

  SOLUTION 2 : Read the frames from http address
  while(true)
  
  startTime=System.currentTimeMillis() ;

          URL url = new URL("h t t p://[IP]/-wvhttp-01-/image.cgi");
  
          URLConnection con = url.openConnection();
  
          BufferedImage image = ImageIO.read(con.getInputStream());   
  
          showImage(image);
  
          estimatedTime=System.currentTimeMillis()-startTime;
  
          System.out.println(estimatedTime);
  
          Thread.sleep(5);
  
  }

  This strategy simply grabs the frame from the url that the camera provides. The code is in Java but the results are the same in C++ with the curl library.
  This solution avoids the delay of the first solution however it takes little more than 100 ms to grab each frame, which means that I can only achieve on average 10 FPS.

  I would like to know how can I read the video using c++ or another library developed in c++ ?

• How do I keep black areas black with ffmpeg ?

  11 janvier 2018, par Aurelius Schnitzler

  When encoding GoPro videos with ffmpeg using

  ffmpeg -i Goprovideo.mp4 -pix_fmt yuv420p -vf scale=1920:-1,crop=1920:1080:0:362 Goprovideo-out.mp4

  I noticed that the videos do not only get much smaller, but also in some cases do black areas lose intensity. So what was black is now grey. Not to an extreme, but slightly noticable.

  How do I keep black areas black with ffmpeg ?

• How to convert raw camera Android data into usual mpeg4 by ffmpeg ?

  12 octobre 2014, par trololo

  I can recieve raw camera data :

   fos = new FileOutputStream (new File(Environment.getExternalStorageDirectory().getPath() + "/video_raw.raw"));
  
  _.mCamera.setPreviewCallback(new Camera.PreviewCallback() {
  
        public synchronized void onPreviewFrame(byte[] data, Camera camera) {
  
  
  
              try {
  
                  if (fos != null)
  
                      fos.write(data);//I can save data to a file
  
  //Environment.getExternalStorageDirectory().getPath() + "/video_raw.raw"
  
                  } catch (IOException e1) {
  
                  // TODO Auto-generated catch block
  
                  e1.printStackTrace();
  
              }
  
  
  
            try{
  
                camera.addCallbackBuffer(data);
  
            }catch (Exception e) {
  
                Log.e("CameraTest", "addCallbackBuffer error");
  
                return;
  
            }
  
            return;
  
        }
  
    });

  and trying to use this library to manipulate with video(audio)-data

  File dir =  new File(_.mediaFile).getParentFile();
  
              FfmpegController fc = new FfmpegController(this, dir);
  
              Clip clip_in = new Clip(Environment.getExternalStorageDirectory().getPath() + "/video_raw.raw");
  
              clip_in.height = 480;
  
              clip_in.width = 720;
  
              clip_in.videoCodec = "rawvideo";
  
              clip_in.videoFilter= "rawvideo";
  
              Clip clip_out = new Clip(Environment.getExternalStorageDirectory().getPath() + "/video15a.mp4");
  
               //put flags in clip
  
              clip_out.videoFps = "30";
  
              clip_out.width = 480;
  
              clip_out.height = 320;
  
              clip_out.videoCodec = "libx264";
  
              clip_out.audioCodec = "copy";
  
              fc.processVideo(clip_in, clip_out, false, new ShellUtils.ShellCallback() {
  
              @Override
  
              public void shellOut(String shellLine) {
  
                  System.out.println("MIX> " + shellLine);
  
              }
  
  
  
              @Override
  
              public void processComplete(int exitValue) {
  
  
  
                  if (exitValue != 0) {
  
                      System.err.println("concat non-zero exit: " + exitValue);
  
                      Log.d("ffmpeg","Compilation error. FFmpeg failed");
  
                      Toast.makeText(AMain.this, "result: ffmpeg failed", Toast.LENGTH_LONG).show();
  
                  } else {
  
                  }
  
              }
  
          });

  Link to the project :
  https://github.com/guardianproject/android-ffmpeg-java

  This code works correctly for any videofile which created before (the other apps). BUt this oce doesn’t work in my case. How to fix it ?