OpenCV VideoCapture not opens file ios - ios

Question

I've saved a video to a file using:
NSString *documentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
documentsDirectory = [documentsDirectory stringByAppendingPathComponent:#"test9.avi"];
NSLog(#"Open to: %#", documentsDirectory);
std::string fileName([documentsDirectory cString], [documentsDirectory cStringLength]);
videoWriter = new cv::VideoWriter(fileName, CV_FOURCC('H', 'F', 'Y', 'U'), 25, cvSize(288,352),1);
But I can't open this with VideoCapture:
NSLog(#"Load the video");
videoCapture = new cv::VideoCapture();
NSLog(#"Video loaded");
if (videoCapture->open(fileName))
{
NSLog(#"Opened");
}
else {
NSLog(#"Failed to open");
}
There is no error from the VideoCapture itself just my log "Failed to open" ...
Can I somehow get more detailed error log?

Answer 1

cv::VideoCapture capture;
NSString* pathToInputFile = [NSString documentPathByAppendingPath:#"Video/sample_iTunes.mov"];
if(capture.open(std::string([pathToFile UTF8String]))){
NSLog(#"Opened");
}else{
NSLog(#"Failed to open");
}
works fine for me

Answer 2

I met this problem using Swift 3.
Thanks to answers by Kirill and CodeBender, I solved this.
let resourceURL = Bundle.main.url(forResource: "test", withExtension: "MOV")
let openCVVideoCapture = OpenCVVideoCaptureWrapper.init(file: resourceURL?.path)
and following is my OpenCVVideoCaptureWrapper.mm
#implementation OpenCVVideoCaptureWrapper {
cv::VideoCapture video;
}
- (instancetype)initWithFile:(NSString*) filePath {
std::string cvFilePath = [filePath UTF8String];
video = cv::VideoCapture(cvFilePath);
if (!video.isOpened()) NSLog(#"Could not open file");
return self;
}
#end

Answer 3

This snippet worked for me in Xcode 10, Swift 4. Thanks to #Nathan Tuggy.
- (void)openVideoFile:(NSURL *)fileName {
NSString *filename = fileName.path;
std::string filePath = [filename UTF8String];
cv::VideoCapture capture(filePath);
if (!capture.isOpened()) {
printf("#Error Opening video file");
// failed, print error message
}
else {
printf("File Opened");
}
}

Answer 4

While Kirill's answer would have worked when it was posted, that is no longer the case now.
The following works in Xcode 8.2.1, replacing the documentPathByAppendingPath function that is no longer available.
cv::VideoCapture cap;
NSString *path = [[NSBundle mainBundle] pathForResource:#"MyVideo" ofType:#"MOV"];
if ( cap.open ( std::string( path.UTF8String ) ) ) {
NSLog(#"Opened");
} else {
NSLog(#"Failed to open");
}