Given a URL to a movie, how can retrieve it's info?

问题

Under iOS, I need to get the codec used to make the move (H.264, MJPEG and so on), the movies' width and height, the file size, and the number of frames in the movie. I tried using AVAsset for the movie duration and such but the duration was always zero. Same for the width/height. I also tried using a movie player controller but that did not work either (see code below). The docs are a bit confusing and with multiple ways of getting to the same place you can't seem to get to the same spot.

Has anyone got the above information working properly? I am sure I am missing a few things but I was hoping for sample code and/or pointers?

Edit: I added a better code example. But, there are questions that remain. How do I get the creation date of the movie, the codec used to compress it and the movie's file size? Anybody figure these out?

Thanks

- (IBAction)getMovieInfo 
{
    int         hours = 0, minutes = 0, seconds = 0;


    NSURL* sourceMovieURL = [NSURL URLWithString:@"http://trailers.apple.com/movies/summit/stepuprevolution/stepuprevolution-tlr1_h480p.mov"];
    AVURLAsset* movieAsset = [AVURLAsset URLAssetWithURL:sourceMovieURL options:nil];

    NSArray *tracks = [movieAsset tracksWithMediaType:AVMediaTypeVideo];

    if ([tracks count] != 0) {
        AVAssetTrack *videoTrack = [tracks objectAtIndex:0];

        NSTimeInterval      durationSeconds = CMTimeGetSeconds([movieAsset duration]);
        CGSize              videoSize = videoTrack.naturalSize;

        //
        // Let's get the movie's meta data
        //

        // Start with the duration of the movie
        hours = durationSeconds / 3600;
        minutes = durationSeconds / 60;
        seconds = (int)durationSeconds % 60;
        durationLabel.text = [NSString stringWithFormat:@"%d:%d:%d", hours, minutes, seconds];

        // Next is the creation (posting) date of the movie
        //postedLabel.text = AVMetadataQuickTimeUserDataKeyCreationDate;

        //The resolution of the movie
        resolutionLabel.text = [NSString stringWithFormat:@"%g x %g", videoSize.width, videoSize.height];

        // The frame rate of the movie
        rateLabel.text = [NSString stringWithFormat:@"%g fps", [videoTrack nominalFrameRate]];

        // The frame count of the movie
        countLabel.text = [NSString stringWithFormat:@"%g", [videoTrack nominalFrameRate] * durationSeconds];

        // Get the codec used to compress the movie



        // And lastly, let's generate a thumbnail of the movie
        AVAssetImageGenerator *imageGenerator = [[AVAssetImageGenerator alloc] initWithAsset:movieAsset];

        if (imageGenerator != NULL) {

            CMTime      thumbPoint = CMTimeMakeWithSeconds(15.0, 600);
            NSError     *error = nil;

            CGImageRef thumbnail = [imageGenerator copyCGImageAtTime:thumbPoint actualTime:nil error:&error];

            if (thumbnail != NULL) {
                // Convert CGImage thumbnail to UIImage and then scale it.
                UIImage *tempImage = [[UIImage alloc] initWithCGImage:thumbnail];

                if (tempImage != NULL) {
                    // Let's scale the image and put the it into the imageview.                
                    self.thumbDisplay.image=[self scaleAndRotateImage:tempImage];

                    CGImageRelease(thumbnail);
                }
            }
        }
    }
}

- (UIImage *)scaleAndRotateImage:(UIImage *)image {

    CGImageRef  imgRef = image.CGImage;

    CGFloat     width = 135.0;
    CGFloat     height = 75.0;


    CGAffineTransform transform = CGAffineTransformIdentity;
    CGRect bounds = CGRectMake(0, 0, width, height);

    CGFloat scaleRatio = bounds.size.width / width;
    CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef));
    CGFloat boundHeight;
    UIImageOrientation orient = image.imageOrientation;

    switch (orient) {

        case UIImageOrientationUp: //EXIF = 1
            transform = CGAffineTransformIdentity;
            break;

        case UIImageOrientationUpMirrored: //EXIF = 2
            transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0);
            transform = CGAffineTransformScale(transform, -1.0, 1.0);
            break;

        case UIImageOrientationDown: //EXIF = 3
            transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height);
            transform = CGAffineTransformRotate(transform, M_PI);
            break;

        case UIImageOrientationDownMirrored: //EXIF = 4
            transform = CGAffineTransformMakeTranslation(0.0, imageSize.height);
            transform = CGAffineTransformScale(transform, 1.0, -1.0);
            break;

        case UIImageOrientationLeftMirrored: //EXIF = 5
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width);
            transform = CGAffineTransformScale(transform, -1.0, 1.0);
            transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
            break;

        case UIImageOrientationLeft: //EXIF = 6
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeTranslation(0.0, imageSize.width);
            transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
            break;

        case UIImageOrientationRightMirrored: //EXIF = 7
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeScale(-1.0, 1.0);
            transform = CGAffineTransformRotate(transform, M_PI / 2.0);
            break;

        case UIImageOrientationRight: //EXIF = 8
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0);
            transform = CGAffineTransformRotate(transform, M_PI / 2.0);
            break;

        default:
            [NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"];

    }

    UIGraphicsBeginImageContext(bounds.size);
    CGContextRef context = UIGraphicsGetCurrentContext();

    if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft) {
        CGContextScaleCTM(context, -scaleRatio, scaleRatio);
        CGContextTranslateCTM(context, -height, 0);
    } else {
        CGContextScaleCTM(context, scaleRatio, -scaleRatio);
        CGContextTranslateCTM(context, 0, -height);
    }

    CGContextConcatCTM(context, transform);

    CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);
    UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return imageCopy;
}

回答1:

NSURL's method getResourceValue:forKey:error allows you to get total number of bytes:

NSURL *fileUrl = [NSURL fileURLWithPath:filePath];
NSString *size = NULL;
[fileUrl getResourceValue:&size forKey:NSURLFileSizeKey error:nil];
NSLog(@"Bytes : %@",size);

It is good practice to check for any errors returned.

回答2:

Try:

CMTime lengthTime = [movieAsset duration];
Float64 seconds = CMTimeGetSeconds(lengthTime);
NSLog(@"Asset is %g seconds long", seconds);

来源：https://stackoverflow.com/questions/11075795/given-a-url-to-a-movie-how-can-retrieve-its-info