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Maybe you could try inserting a printf("Frame found\n") inside the for(;;) to see if it is actually capturing frames. Or even better:
if(colourImage == NULL) {
printf("Warning - got NULL colourImage\n");
continue;
}
cvNamedWindow( "test", 1);
cvShowImage( "test", colourImage );
cvWaitKey( 0 );
cvDestroyWindow( "test" );
Then see if you get any windows, and if they contain the right contents.
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My bet is that cvCreateVideoWriter returns NULL. Just step through it to see if it's true. In that case, the problem is probably with CV_FOURCC(..) which doesnt find the codec and force a return 0;
you can try using -1 instead of CV_FOURCC. There is gonna be a prompt during runtime for you to chose the appropriate codec
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I've a problem under MacOs 10.4. When I try to execute this row
CvVideoWriter *writer = cvCreateVideoWriter(
"out.avi",
CV_FOURCC('M', 'J', 'P', 'G'),
fps,
imgSize
);
i've this problem:
OpenCV ERROR: Internal error (Cannot create data reference from file name)
in function icvCreateVideoWriter, cvcap_qt.cpp(1291)
Terminating the application...
any idea?
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When i google this problem i meet an answer: "OpenCV on mac os x don`t support avi write until it will be compiled with a ffmpeg"
For me seem to wrok this solution
http://article.gmane.org/gmane.comp.lib.opencv/16005
You need to provide the full path to
the file with the movie in
cvCreateVideoWriter. I don't know
whether it's only an Mac OS X port
issue, but might be, since
QTNewDataReferenceFromFullPathCFString
from the QT backend is used.
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Friends I faced the same problem; the methods suggested by Eric does work. The problem, i think lies with the availability of the codecs. Thanks to all of you....
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Hi ,
I have the following code , and NONE of the functions are returning NULL, so I guess everything is proper.
But still the file size of the test.avi file is 0 bytes
CvCapture *pCapturedImage = cvCreateCameraCapture(0); // get the default camera, for me it is a webcam
// Get the avi file name
CString strFileName = objFileDlg.GetPathName()+".avi"; // test.avi
int isColor = 1;
int fps = 25; // or 30
int frameW = 640; // 744 for firewire cameras
int frameH = 480; // 480 for firewire cameras
CvVideoWriter *pVideoWriter = cvCreateVideoWriter(strFileName.GetBuffer(),
-1, // I am choosing the uncompressed format**
fps,cvSize(frameW,frameH),isColor);
// pVideoWriter does not return NULL , that means its succesful
cvNamedWindow("mainWin",CV_WINDOW_AUTOSIZE);
IplImage *pImage = 0;
int nFrames = 50;
for(int i=0;i<nFrames;i++)
{
cvGrabFrame(pCapturedImage); // capture a frame
pImage=cvRetrieveFrame(pCapturedImage); // retrieve the captured frame
cvWriteFrame(pVideoWriter,pImage); // add the frame to the file
cvShowImage("mainWin",pImage); // NO IMAGE SHOWS UP
cvWaitKey(20);
}
cvDestroyWindow("mainWin");
cvReleaseVideoWriter(&pVideoWriter);
Please let me know what am I missing out.
Thanks,
Sujay
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hey This code works in DevC++ try it:
#include<cv.h>
#include<highgui.h>
#include<cvaux.h>
#include<cvcam.h>
#include<cxcore.h>
int main()
{
CvVideoWriter *writer = 0;
int isColor = 1;
int fps = 5; // or 30
int frameW = 1600; //640; // 744 for firewire cameras
int frameH = 1200; //480; // 480 for firewire cameras
//writer=cvCreateVideoWriter("out.avi",CV_FOURCC('P','I','M','1'),
// fps,cvSize(frameW,frameH),isColor);
writer=cvCreateVideoWriter("out.avi",-1,
fps,cvSize(frameW,frameH),isColor);
IplImage* img = 0;
img=cvLoadImage("CapturedFrame_0.jpg");
cvWriteFrame(writer,img); // add the frame to the file
img=cvLoadImage("CapturedFrame_1.jpg");
cvWriteFrame(writer,img);
img=cvLoadImage("CapturedFrame_2.jpg");
cvWriteFrame(writer,img);
img=cvLoadImage("CapturedFrame_3.jpg");
cvWriteFrame(writer,img);
img=cvLoadImage("CapturedFrame_4.jpg");
cvWriteFrame(writer,img);
img=cvLoadImage("CapturedFrame_5.jpg");
cvWriteFrame(writer,img);
cvReleaseVideoWriter(&writer);
return 0;
}
I compiled it and ran it, works fine.
(I did not see above whether you got your answer or not .. but for this particular thing I worked very hard earlier and suddenly I just did it, from some code snippets.)
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This code worked fine:
cv.h
highgui.h
cvaux.h
cvcam.h
cxcore.h
int main(){
CvVideoWriter *writer = 0;
int isColor = 1;
int fps = 5; // or 30
IplImage* img = 0;
img=cvLoadImage("animTest_1.bmp");
int frameW = img->width; //640; // 744 for firewire cameras
int frameH = img->height; //480; // 480 for firewire cameras
writer=cvCreateVideoWriter("out.avi",-1,
fps,cvSize(frameW,frameH),1);
cvWriteFrame(writer, img); // add the frame to the file
char *FirstFile,fF[20]="",*fileNoStr,fns[4]="";
fileNoStr=fns;
for(int fileNo;fileNo<100;fileNo++){
FirstFile=fF;
itoa(fileNo,fileNoStr,10);
FirstFile=strcat ( FirstFile,"animTest_");
FirstFile=strcat ( FirstFile,fileNoStr);
FirstFile=strcat ( FirstFile,".bmp");
printf(" \n%s .",FirstFile);
img=cvLoadImage(FirstFile);
cvWriteFrame(writer, img);
}
cvReleaseVideoWriter(&writer);
return 0;
}
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I think the problem you're encountering is that your "for" loop never ends; therefore, "cvReleaseVideoWriter(&writer);" and "cvReleaseCapture(&input);" never get called. Try something like "for(int i=0; i<200; i++)" and see if you end up with a working video.
Often video is written to a temporary files before being finalized on disk. If your file isn't finalized, there won't be anything to see.
Hope that helps.
