OpenCV Video capture and fps problem

Question

I\'m capturing video from my webcam using OpenCV on MacOSX. It works fine but when I try to play on QuickTime my captured video it plays too fast. i.e. I capture from camera

Answer 1

I confirm that 10 fps is standard, although I believe it may be because you don't have a camera which captures at more than 10 fps (which is likely the issue).

This is still strange because I'm using waitkey(30), which should be 33fps, but it's precisely 10.

Answer 2

Use cvCreateVideoWriter(filename, fourcc, fps, frame size, is color) with fps = 10 , fps = 20 and different values. If you already know the fps value of frames coming from camera use that.

Problem is that you are getting less frames per second from camera and you're writing more frames to video file

Regards, Saleh.

Answer 3

I was having similar performance as you mentioned (about 10fps) and found that successive retrieveFrame() calls were taking forever. I found that getCaptureProperty(CV_CAP_PROP_FPS) was at a default value of 0. I changed this value to 25 using setCaptureProperty(CV_CAP_PROP_FPS,25.0) and was able to capture much faster.

Answer 4

Could be that compressing the captured video and saving it to a file is too CPU intensive. If that's the case then you really only see 10 FPS in the cvNamedWindow, and only 10 FPS are written to the file. Specifiying 25 FPS in the file will naturally speed playback up some.

To see if that's really your problem, you could try to save the image data only in memory. I've not tried it out, but I think you'd do that with cvCloneImage().

You could also try some other format with a lower CPU overhead to save your video:

CV_FOURCC('P','I','M','1')    = MPEG-1 codec
CV_FOURCC('M','J','P','G')    = motion-jpeg codec (does not work well)
CV_FOURCC('M', 'P', '4', '2') = MPEG-4.2 codec
CV_FOURCC('D', 'I', 'V', '3') = MPEG-4.3 codec
CV_FOURCC('D', 'I', 'V', 'X') = MPEG-4 codec
CV_FOURCC('U', '2', '6', '3') = H263 codec
CV_FOURCC('I', '2', '6', '3') = H263I codec
CV_FOURCC('F', 'L', 'V', '1') = FLV1 codec