QTMovie at 29.97 with QTMakeTime

Question

I'm trying to use QTKit to convert a list of images to a quicktime movie. I've figured out how to do everything except get the frame rate to 29.97. Through other forums and resources, the trick seems to be using something like this:

QTTime frameDuration = QTMakeTime(1001, 30000)

However, all my attempts using this method, or even (1000, 29970) still produce a movie at 30fps. This fps is what shows up when playing with Quicktime player.

Any ideas? Is there some other way to set the frame rate for the entire movie once its created?

Here's some sample code:

NSDictionary *outputMovieAttribs = [NSDictionary dictionaryWithObjectsAndKeys:@"jpeg", QTAddImageCodecType, [NSNumber numberWithLong:codecHighQuality], QTAddImageCodecQuality, nil];
QTTime frameDuration = QTMakeTime(1001, 30000);
QTMovie *outputMovie = [[QTMovie alloc] initToWritableFile:@"/tmp/testing.mov" error:nil];
[outputMovie setAttribute:[NSNumber numberWithBool:YES] forKey:QTMovieEditableAttribute];
[outputMovie setAttribute:[NSNumber numberWithLong:30000] forKey:QTMovieTimeScaleAttribute];

if (!outputMovie) {
    printf("ERROR: Chunk: Could not create movie object:\n");
} else {
    int frameID = 0;
    while (frameID < [framePaths count]) {
        NSAutoreleasePool *readPool = [[NSAutoreleasePool alloc] init];
        NSData *currFrameData = [NSData dataWithContentsOfFile:[framePaths objectAtIndex:frameID]];
        NSImage *currFrame = [[NSImage alloc] initWithData:currFrameData];

        if (currFrame) {
            [outputMovie addImage:currFrame forDuration:frameDuration withAttributes:outputMovieAttribs];
            [outputMovie updateMovieFile];
            NSString *newDuration = QTStringFromTime([outputMovie duration]);
            printf("new Duration: %s\n", [newDuration UTF8String]);
            currFrame = nil;
        } else {
            printf("ERROR: Could not add image to movie");
        }
        frameID++;
        [readPool drain];
    }
}

NSString *outputDuration = QTStringFromTime([outputMovie duration]);
printf("output Duration: %s\n", [outputDuration UTF8String]);

Answer 1

Ok, thanks to your code, I could solve the issue. I was using the development tool called Atom Inpector to see that the data structure looked totally different than the movies I am currently working with. As I said, I never created a movie from images as you do, but it seems that this is not the way to go if you want to have a movie afterwards. QuickTime recognizes the clip as "Photo-JPEG", so not a normal movie file. The reason for this seems to be, that the added pictures are NOT added to a movie track but just somewhere in the movie. This can also be seen with Atom Inspector. With the "movieTimeScaleAttribute", you set a timeScale that is not used!

To solve the issue I changed the code just a tiny bit.

NSDictionary *outputMovieAttribs = [NSDictionary dictionaryWithObjectsAndKeys:@"jpeg", 
                      QTAddImageCodecType, [NSNumber numberWithLong:codecHighQuality],
                      QTAddImageCodecQuality,[NSNumber numberWithLong:2997], QTTrackTimeScaleAttribute, nil];

QTTime frameDuration = QTMakeTime(100, 2997);
QTMovie *outputMovie = [[QTMovie alloc] initToWritableFile:@"/Users/flo/Desktop/testing.mov" error:nil];
[outputMovie setAttribute:[NSNumber numberWithBool:YES] forKey:QTMovieEditableAttribute];
[outputMovie setAttribute:[NSNumber numberWithLong:2997] forKey:QTMovieTimeScaleAttribute];

Everything else is unaltered. Oh, by the way. To print the timeValue and timeScale, you could also do :

NSLog(@"new Duration timeScale : %ld timeValue : %lld \n", 
       [outputMovie duration].timeScale, [outputMovie duration].timeValue);

This way you can see better if your code does as desired.

Hope that helps! Best regards