Question

我是opencv的新手，写入视频文件时遇到问题。基本上我正在从高清网络摄像头读取并写入avi。可运行的代码：

#include "cv.h"
#include "highgui.h"
int main(int argc, char** argv){
    CvCapture* capture=NULL;
    capture=cvCreateCameraCapture(0);
    if(!capture){
            return -1; 
    }   
    IplImage *bgr_frame=cvQueryFrame(capture);
    double fps=cvGetCaptureProperty(capture, CV_CAP_PROP_FPS);
    CvSize size=cvSize((int)cvGetCaptureProperty(capture, CV_CAP_PROP_FRAME_WIDTH),
                            (int)cvGetCaptureProperty(capture, CV_CAP_PROP_FRAME_HEIGHT));        
CvVideoWriter* writer=cvCreateVideoWriter(argv[1],
                                            CV_FOURCC('M','J','P','G'),
                                            fps,
                                            size);
    cvNamedWindow("Video", CV_WINDOW_AUTOSIZE); 
    while((bgr_frame=cvQueryFrame(capture))){
            cvWriteFrame(writer, bgr_frame);
            cvShowImage("Video", bgr_frame);
            char c=cvWaitKey(60);
            if(c==27){
                    break;
            }           
    }           
    cvReleaseVideoWriter(&writer);
    cvReleaseImage(&bgr_frame);
    cvReleaseCapture(&capture);
    return 0;
}

运行时，我收到错误

Output #0, avi, to 'test.avi':
Stream #0.0: Video: mjpeg, yuvj420p, 1280x720, q=2-31, 117964 kb/s, 90k tbn
[mjpeg @ 0x7fd55b805600] bitrate tolerance too small for bitrate
WARNING: Could not create empty movie file container.
OpenCV Error: Assertion failed (dst.data == dst0.data) in cvCvtColor, file /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_graphics_opencv/opencv/work/OpenCV-2.3.1/modules/imgproc/src/color.cpp, line 3175
terminate called throwing an exceptionAbort trap: 6

相机是Macbook上的高清网络摄像头。这个相机会导致问题吗？如果是这样，我可以将比特率容差设置得更低吗？我是opencv的新手。谢谢！

顺便说一下，当argv [1] .avi不存在时，CvVideoWriter可以创建一个新文件吗？

Answer 1

是的，cvCreateVideoWriter会在尚不存在时创建新文件。

因为每个网络摄像头驱动程序都没有实现FPS检测代码，所以会出现问题。在Mac上尝试使用一个断言添加代码：

double fps=(double)cvGetCaptureProperty(capture, CV_CAP_PROP_FPS);
assert(fps>0.0);

运行它：

./w x.avi
Assertion failed: (fps>0.0), function main, file w.cpp, line 11.
Abort trap: 6

带有FPS的AVI文件无法运行，这就是它未创建的原因。

使用opencv录制时，误码率误差对于比特率来说太小了

1 个答案: