I recently installed OpenCV 2.4.2 in Ubuntu 12.04.
cap = VideoCapture(0)
is working. but I can't grab frames from some video source.
cap = VideoCapture("input.avi")
img = cap.read()
gives me a numpy with all zero elements.
I have also installed ffmpeg 0.11, Latest snapshot of x264, v4l-0.8.8 (All are latest stable versions)
cmake -D WITH_QT=ON -D WITH_FFMPEG=ON -D WITH_OPENGL=ON -D WITH_TBB=ON -D BUILD_EXAMPLES=OFF WITH_V4L=ON ..
make
sudo make install
When I do cmake, I get this
-- Detected version of GNU GCC: 46 (406)
-- Found OpenEXR: /usr/lib/libIlmImf.so
-- Looking for linux/videodev.h
-- Looking for linux/videodev.h - not found
-- Looking for linux/videodev2.h
-- Looking for linux/videodev2.h - found
-- Looking for libavformat/avformat.h
-- Looking for libavformat/avformat.h - found
-- Looking for ffmpeg/avformat.h
-- Looking for ffmpeg/avformat.h - not found
-- checking for module 'tbb'
-- package 'tbb' not found
And
-- Video I/O:
-- DC1394 1.x: NO
-- DC1394 2.x: YES (ver 2.2.0)
-- FFMPEG: YES
-- codec: YES (ver 54.23.100)
-- format: YES (ver 54.6.100)
-- util: YES (ver 51.54.100)
-- swscale: YES (ver 2.1.100)
-- gentoo-style: YES
-- GStreamer:
-- base: YES (ver 0.10.36)
-- app: YES (ver 0.10.36)
-- video: YES (ver 0.10.36)
-- OpenNI: NO
-- OpenNI PrimeSensor Modules: NO
-- PvAPI: NO
-- UniCap: NO
-- UniCap ucil: NO
-- V4L/V4L2: Using libv4l (ver 0.8.8)
-- XIMEA: NO
-- Xine: NO
I looked for videodev.h, etc
- /usr/include/linux/videodev2.h exists
- /usr/include/libavformat/avformat.h exists
- /usr/local/include/libavformat/avformat.h exists
But I couldn't find ffmpeg/avformat.h
What's the problem here?
So, I realized there was some problem with ffmpeg. and I rebuilt and installed ffmpeg and then changed flags for cmake to make opencv.
For ffmpeg,
./configure --enable-gpl --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libxvid --enable-nonfree --enable-postproc --enable-version3 --enable-x11grab
make
sudo make install
For OpenCV,
cmake -D CMAKE_BUILD_TYPE=RELEASE ..
make
sudo make install
Here's the complete script to install OpenCV 2.4.2 https://github.com/jayrambhia/Install-OpenCV/blob/master/Ubuntu/2.4/opencv2_4_2.sh
and here's my blogpost about OpenCV 2.4.2 installation in detail http://jayrambhia.com/blog/install-opencv-2-4-in-ubuntu-12-04-precise-pangolin/
To run a full installation of OpenCV try the following:
sudo apt-get install libopencv-dev python-opencv
For more details check out the following link http://milq.github.io/install-opencv-ubuntu-debian/
来源：https://stackoverflow.com/questions/11444926/videocapture-is-not-working-in-opencv-2-4-2