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• OpenCV Reporting TBR instead of FPS when using capture.get(CV_CAP_PROP_FPS)

  22 février 2012, par Malife

  I have several videos that I am trying to process using OpenCV and Qt 4.7.4 on Mac OS 10.6.8 (Snow Leopard). If I create a cv::VideoCapture object and then query for the frame rate related to such video, what I get back is the TBR and not FPS.

  For instance if use ffprobe Video1.mp4 what I get is :

  >> ffprobe Video1.mp4      
  
  ffprobe version 0.7.8, Copyright (c) 2007-2011 the FFmpeg developers
  
  built on Nov 24 2011 14:31:00 with gcc 4.2.1 (Apple Inc. build 5666) (dot 3)
  
  configuration: --prefix=/opt/local --enable-gpl --enable-postproc --enable-swscale --   
  
  enable-avfilter --enable-libmp3lame --enable-libvorbis --enable-libtheora --enable-
  
  libdirac --enable-libschroedinger --enable-libopenjpeg --enable-libxvid --enable-libx264 
  
  --enable-libvpx --enable-libspeex --mandir=/opt/local/share/man --enable-shared --
  
  enable-pthreads --cc=/usr/bin/gcc-4.2 --arch=x86_64 --enable-yasm
  
  libavutil    50. 43. 0 / 50. 43. 0
  
  libavcodec   52.123. 0 / 52.123. 0
  
  libavformat  52.111. 0 / 52.111. 0
  
  libavdevice  52.  5. 0 / 52.  5. 0
  
  libavfilter   1. 80. 0 /  1. 80. 0
  
  libswscale    0. 14. 1 /  0. 14. 1
  
  libpostproc  51.  2. 0 / 51.  2. 0
  
  
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'Video1.mp4':
  
  Metadata:
  
  major_brand     : isom
  
  minor_version   : 0
  
  compatible_brands: mp41avc1qt  
  
  creation_time   : 2012-01-09 23:09:43
  
  encoder         : vlc 1.1.3 stream output
  
  encoder-eng     : vlc 1.1.3 stream output
  
  Duration: 00:10:10.22, start: 0.000000, bitrate: 800 kb/s
  
  Stream #0.0(eng): Video: h264 (Baseline), yuvj420p, 704x480 [PAR 10:11 DAR 4:3], 798 
  
  kb/s, 27.71 fps, 1001 tbr, 1001 tbn, 2002 tbc
  
  Metadata:
  
    creation_time   : 2012-01-09 23:09:43

  Which correctly reports FPS = 27.71 and TBR = 1001. Nevertheless if I use the following OpenCV code to query for the FPS :

  QString filename = QFileDialog::getOpenFileName(this,
  
                                          "Open Video",
  
                                          "Video Files (*.mp4, *.mpg)");
  
  
  
  capture.release();
  
  capture.open(filename.toAscii().data());
  
  
  
  if (!capture.isOpened()){
  
      qDebug() <<"Error when opening the video!";
  
      return;
  
  }
  
  
  
  
  
  qDebug() << "Frame Rate:" << capture.get(CV_CAP_PROP_FPS);
  
  qDebug() << "Num of Frames:" << capture.get(CV_CAP_PROP_FRAME_COUNT);
  
  qDebug() << "OpenCV Version" << CV_VERSION;

  The output I get is :

  Frame Rate: 1001 
  
  Num of Frames: 610832 
  
  OpenCV Version 2.3.1 

  Which reports the TBR instead of the FPS. This behavior is consistent when I try to open different videos.

  I checked OpenCV's bug tracker and I also found this stack overflow question to be a similar but not quite the same problem, so I am at a loss to what to do next. Any hint or idea is most welcome since I've tried lots of things and seem to be getting nowhere.

• Converting an RTP stream to RTSP or HTTP on Android

  15 mars 2012, par MobilityLab

  I have been trying to write and Android App for a specific application. Basically, I will have a device on the LAN that will be transmitting RTP packets containing H.264 encoded video, where all parameters are predefined. I need to capture these packets and display the video on an Android phone/tablet. My original thought was to capture all the RTP packets and add any additional packets that are necessary to supply the MediaPlayer class with enough information to display the video via RTSP.

  While I started to investigate that possibility, I found this, but the question remains unanswered.

  So, my question is, what advice/suggestions does anyone have for converting a RTP stream into a RTSP or HTTP context that MediaPlayer will understand. Does anyone know how to configure FFMPEG to do this ? Perhaps another tool that I can compile to Android, or a Java library that has this functionality.

  If you think I will have to manually code this process, any advice or references would be greatly appreciated.

  Thanks,

  Andrew @ MobilityLab

• Android FFmpeg video lag

  20 mars 2012, par user1281499

  I am working on to get a video player built for android using ffmpeg.
  I went through the following links to start building the player.I also went through the tutorial for building a player using ffmpeg and SDL by dranger on ffmpeg site. But I am facing problem of audio being not sync with the video for high resolution videos. For low resolution videos the audio and video both are in sync. I also saw a question addressing the problem with sws_scale() in ffmpeg (it may be slow), but as ffmpeg tutorial tells us that it is optimized, what can be the problem. I am using a surface and drawing the generated bitmap on the canvas. Is there any other method we should try.

  http://rockplayer.freecoder.org/tech_en.html

  http://dranger.com/ffmpeg/