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POOpenCV Reporting TBR instead of FPS when using capture.get(CV_CAP_PROP_FPS)
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  1. POOpenCV Reporting TBR instead of FPS when using capture.get(CV_CAP_PROP_FPS)
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    copied!<p>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 <code>cv::VideoCapture</code> object and then query for the frame rate related to such video, what I get back is the TBR and not FPS. </p> <p>For instance if use <code>ffprobe Video1.mp4</code> what I get is:</p> <pre><code>&gt;&gt; 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 </code></pre> <p>Which correctly reports FPS = 27.71 and TBR = 1001. Nevertheless if I use the following OpenCV code to query for the FPS:</p> <pre><code>QString filename = QFileDialog::getOpenFileName(this, "Open Video", "Video Files (*.mp4, *.mpg)"); capture.release(); capture.open(filename.toAscii().data()); if (!capture.isOpened()){ qDebug() &lt;&lt;"Error when opening the video!"; return; } qDebug() &lt;&lt; "Frame Rate:" &lt;&lt; capture.get(CV_CAP_PROP_FPS); qDebug() &lt;&lt; "Num of Frames:" &lt;&lt; capture.get(CV_CAP_PROP_FRAME_COUNT); qDebug() &lt;&lt; "OpenCV Version" &lt;&lt; CV_VERSION; </code></pre> <p>The output I get is:</p> <pre><code>Frame Rate: 1001 Num of Frames: 610832 OpenCV Version 2.3.1 </code></pre> <p>Which reports the TBR instead of the FPS. This behavior is consistent when I try to open different videos. </p> <p>I checked OpenCV's <a href="http://code.opencv.org/projects/opencv/issues" rel="nofollow noreferrer">bug tracker</a> and I also found <a href="https://stackoverflow.com/questions/4352939/opencv-doesnt-report-accurate-frame-rate-count">this</a> 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.</p>
 

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