Camera input video compression

asked 2014-01-16 19:27:54 -0600

cmastudios

6 ●3

updated 2014-01-17 11:08:05 -0600

unxnut

1644 ●4 ●9 ●28 http://www.cs.umsl.edu...

I want the camera to compress the video using VideoCapture class. However, I cannot figure out how to set the property to enable camera to start compressing video. I have tried to set the property CV_CAP_PROP_FOURCC with VideoCapture::set but that requires a double as the parameter but CV_CAP_PROP_FOURCC is supposed to take char[4]. Can someone please help?

answered 2014-01-18 03:34:18 -0600

Moster
1716 ●5 ●24

There is a function CV_FOURCC that can be used like that:

CV_FOURCC('M','J','P','G')

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The OP wants to know how to use VideoCapture::set to set the FOURCC value. set requires a double as parameter but FOURCC is supposed to be a char array.

unxnut ( 2014-01-18 08:36:59 -0600 )edit

So where is the problem? This function returns the right value to be used according to the fourcc code. Its actually returns an integer, but that doesnt matter in this case. The VideoCapture class will take care of that

Moster ( 2014-01-18 13:09:09 -0600 )edit

When attempting to set the property in the fashion VideoCapture::set(CV_CAP_PROP_FOURCC, CV_FOURCC('M','J','P','G')) it returns an error message: HIGHGUI ERROR: V4L: setting property #6 is not supported

unxnut ( 2014-01-18 16:13:40 -0600 )edit

Yes, because setting the compression mode is not supported by every backend.

Moster ( 2014-01-19 14:15:27 -0600 )edit

Check the icvSetPropertyCAM_V4L method in https://github.com/Itseez/opencv/blob/master/modules/highgui/src/cap_v4l.cpp

Moster ( 2014-01-19 14:17:56 -0600 )edit

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