Size in kbytes of AVI of video in C++/OpenCV

Question

Is there a way to know the size of an avi video in OpenCV? There are some videos that are blank and instead of processing them I want to get rid of them by comparing their size to a threshold. For example, if the size of the video is 200 kB or less, then I skip processing that video.

Update:

     CvCapture *capture = cvCreateFileCapture(path);
     IplImage *img = cvQueryFrame( capture );

All videos have the same number of frames but some videos have all blank frames.

CvCapture *capture = cvCreateFileCapture(path); IplImage *imgsize = cvQueryFrame( capture ); — fmvpsenior, Jul 16 '12 at 16:37

score 0 · Accepted Answer · edited May 23 '17 at 12:04

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You can get number of frames by getting CV_CAP_PROP_FRAME_COUNT video property using GetCaptureProperty:

CV_CAP_PROP_FRAME_COUNT Number of frames in the video file.

To get size of file (video) there is another API - depends on your system (WinAPI, POSIX etc). For example on Windows it's GetFileSizeEx() function.

Also look at this SO discussion.

edited May 23 '17 at 12:04

Community

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answered Jul 16 '12 at 16:37

ArtemStorozhuk

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All the videos have the same number of frames. But some videos have all frames blank. – fmvpsenior Jul 16 '12 at 16:38
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@bestnagi anyway OpenCV is not a I/O library - use another libs/APIs. – ArtemStorozhuk Jul 16 '12 at 16:40
@bestnagi Blank frames, meaning the entire frame is black? – Alex W Jul 16 '12 at 16:51
yes all videos have 50 frames. but some videos have all frames black/blank. – fmvpsenior Jul 16 '12 at 16:53
@bestnagi it's impossible in OpenCV - OpenCV created to solve another problems. – ArtemStorozhuk Jul 16 '12 at 16:54
Thanks. I ended up using the fseek method from the SO discussion. – fmvpsenior Jul 16 '12 at 17:47

Alex W · Answer 2 · 2012-07-16T17:25:15.337

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If you want to get the actual file size, you will have to use fopen() or stat as OpenCV doesn't store this information in a cvCapture object. However, you can detect blank videos like so:

CvCapture *capture = cvCaptureFromAVI( argv[1] );
int numFrames = (int) cvGetCaptureProperty(&capture, CV_CAP_PROP_FRAME_COUNT);

Then just decide if it's blank based on the number of frames.

Relevant Documentation:

http://opencv.willowgarage.com/documentation/reading_and_writing_images_and_video.html?highlight=cvcapture#getcaptureproperty

If the file size is different for the blank videos, but the files have the same number of frames, it's due to video compression via keyframing. That means the best way to detect blank frames is via getting the file size, which is outside of the scope of OpenCV and can easily be accomplished using plain C/C++:

#include <sys/stat.h>
...
struct stat st;
stat(avi_filename, &st);
size = st.st_size;

edited Jul 16 '12 at 17:25

answered Jul 16 '12 at 16:41

Alex W

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I had the same answer - what is new in your answer? – ArtemStorozhuk Jul 16 '12 at 16:43
All the videos have same number of frames 50. But some videos have blank frames. Each frame is black. – fmvpsenior Jul 16 '12 at 16:52
@Astor I use OpenCV in Python and I am currently reading the book for C/C++ and I don't need to Google it because there's documentation. You seem to care more about your reputation than helping the OP.... – Alex W Jul 16 '12 at 17:07
@AlexW my answer is the same as yours so why did you answer it? I have to copy/paste code from that SO link to help OP or what? – ArtemStorozhuk Jul 16 '12 at 17:11
I ended up using the fseek method. Thanks for your help. – fmvpsenior Jul 16 '12 at 17:48

Size in kbytes of AVI of video in C++/OpenCV

2 Answers2