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.