OpenCV VideoCapture Not Opening

Question

I'm trying to use OpenCV's cv2 python bindings on an Amazon server running Ubuntu 14.04 and I can't seem to get VideoCapture to work properly.

I tried opening the default capture as follows:

import cv2
cap = cv2.VideoCapture(0)
cap.isOpened() #Returns false

I tested this on my local machine and it was true as expected, so there is something wrong with my open CV configuration. I've tried a variety of things:

• Using an actual filepath that I confirmed points to an .mp4 file
• Using -1 and 1 in place of 0 on the second line
• Installing ffmpeg (from a ppa as it isn't available by default on Ubuntu 14.04) and rebuilding OpenCV
• Removing my OpenCV directory entirely and rebuilding using the script here
• Verifying and reinstalling various other libraries including x264, gstreamer, and gtk

I'm kind of out of ideas at this point. Any ideas of what could be going wrong?

Edit: OpenCV version is 2.4.9.

Answer 1

I had the same problem and was solved successfully. You should to build OpenCV with WITH_FFMPEG flag:

cmake .. -DCMAKE_BUILD_TYPE=RELEASE -DCMAKE_INSTALL_PREFIX=/usr/local -DWITH_GTK=ON -DWITH_FFMPEG=1 

And you should view "YES" everywhere in section FFMPEG:

Video I/O:
--     DC1394 1.x:                  NO
--     DC1394 2.x:                  YES (ver 2.2.5)
--     FFMPEG:                      YES
--       avcodec:                   YES (ver 57.107.100)
--       avformat:                  YES (ver 57.83.100)
--       avutil:                    YES (ver 55.78.100)
--       swscale:                   YES (ver 4.8.100)
--       avresample:                YES (ver 3.7.0)
--     GStreamer:                   NO
--     OpenNI:                      NO
--     OpenNI PrimeSensor Modules:  NO
--     PvAPI:                       NO
--     GigEVisionSDK:               NO
--     UniCap:                      NO
--     UniCap ucil:                 NO
--     V4L/V4L2:                    NO/YES
--     XIMEA:                       NO
--     Xine:                        NO

If you will not see it then need to install next packages via apt (if you are using Debian or Ubuntu Linux):

sudo apt-get install libav-tools libavcodec-dev libavformat-dev libavutil-dev libswscale-dev libx264-dev