Raspicam的慢帧率捕获视频

Question

I'm trying to use a Raspberry Pi camera to record a video. I want to use openCV to do the recording, because when I have this working I will do some more processing.

I'm using the raspicam/raspicam_cv library from here . I am able to open the camera and read into a cv::Mat, and create a video, but the frame rate is between 1-2 Hz.

My code is here:

#include <ctime>
#include <iostream>
#include <raspicam/raspicam_cv.h>
#include <cstdio>

using namespace std; 

int main ( int argc,char **argv ) {

    time_t timer_begin,timer_end;
    raspicam::RaspiCam_Cv Camera;
    cv::Mat image;
    int nCount=100;

    cout<<"Opening Camera..."<<endl;
    if (!Camera.open()) {cerr<<"Error opening the camera"<<endl;return -1;}

    cout<<"Capturing "<<nCount<<" frames ...."<<endl;
    time ( &timer_begin );

    cv::VideoWriter writer("Avideo.avi", CV_FOURCC('M', 'J', 'P', 'G'), 30, cv::Size(1280,960), true);

 for ( int i=0; i<nCount; i++ ) {
    char name[32] = {0};
        Camera.grab();
        Camera.retrieve ( image);
    writer.write(image);    
    }
    cout<<"Stop camera..."<<endl;
    Camera.release();

    time ( &timer_end ); /* get current time; same as: timer = time(NULL)  */
    double secondsElapsed = difftime ( timer_end,timer_begin );
    cout<< secondsElapsed<<" seconds for "<< nCount<<"  frames : FPS = "<<  ( float ) ( ( float ) ( nCount ) /secondsElapsed ) <<endl;

}

When I run the program raspivid I can see videos which seem to run at 30 Hz which is what I would like to achieve.

I can also only get this code to work using size 1280x960 for some reason.

If anyone could give me some tips that would be great.

Answer 1

The default size of raspicam::RaspiCam_Cv is 1280*960,you can use get to get:

double RaspiCam_Cv::get ( int propId );

for example:

Camera.get(CV_CAP_PROP_FRAME_WIDTH);
Camera.get(CV_CAP_PROP_FRAME_HEIGHT);

If you want other size,you can use set to set:

bool RaspiCam_Cv::set ( int propId, double value );

for example:

Camera.set(CV_CAP_PROP_FRAME_WIDTH,640);
Camera.set(CV_CAP_PROP_FRAME_HEIGHT,480);

The other properties can get/set include:

 * CV_CAP_PROP_FRAME_WIDTH,CV_CAP_PROP_FRAME_HEIGHT,
 * CV_CAP_PROP_FORMAT: CV_8UC1 or CV_8UC3
 * CV_CAP_PROP_BRIGHTNESS: [0,100]
 * CV_CAP_PROP_CONTRAST: [0,100]
 * CV_CAP_PROP_SATURATION: [0,100]
 * CV_CAP_PROP_GAIN: (iso): [0,100]
 * CV_CAP_PROP_EXPOSURE: -1 auto. [1,100] shutter speed from 0 to 33ms
 * CV_CAP_PROP_WHITE_BALANCE_RED_V : [1,100] -1 auto whitebalance
 * CV_CAP_PROP_WHITE_BALANCE_BLUE_U : [1,100] -1 auto whitebalance
 * CV_CAP_PROP_MODE : [1,7] 0 auto mode

PS:The FPS and size of cv::VideoWriter must be same with raspicam::RaspiCam_Cv ,otherwise, cv::VideoWriter will never work.