Question

我试图利用QTKit将图像清单转换成一个快速电影。我详细描述了除达到29.97年标准外,如何做一切工作。通过其他论坛和资源,trick似乎正在使用类似的东西:

QTTime frameDuration = QTMakeTime(1001, 30000)

然而,我使用这种方法的所有尝试,甚至(1,000,29970人)仍在30处制作一部电影。这一缺陷是在与快速参与者玩.时出现的。

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:
");
} 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
", [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
", [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!

为了解决这个问题,我只修改了法典。

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 
", 
       [outputMovie duration].timeScale, [outputMovie duration].timeValue);

这样,如果你的法典符合理想,你就可以更好地看到。

Hope that helps! Best regards

Answer 2

I have never done what you re trying to do, but I can tell you how to get the desired framerate I guess. If you "ask" a movie for its current timing information, you always get a QTTime structure, which contains the timeScale and the timeValue. For a 29.97 fps video, you would get a timeScale of 2997 ( for example, see below ). This is the amount of "units" per second.

So, if the playback position of the movie is currently at exactly 2 seconds, you would get a timeValue of 5994. The frameDuration is therefore 100, because 2997 / 100 = 29.97 fps.

QuickTime cannot handle float values, so you have to convert all the values to a long value by multiplication. By the way, you don t have to use 100, you could also use 1000 and a timeScale of 29970, or 200 as frame duration and 5994 timeScale. That s all I can tell you from what you get if you read timing information from already existing clips. You wrote that this didn t work out for you, but this is how QuickTime works internally. You should look into it again!

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