objective-c – 在ios中连接两个视频

-[NSURL tracksWithMediaType:]: unrecognized selector sent to instance 0x935cf10

2012-08-09 16:26:59.492 videoTest[3920:17903] Terminating app due to uncaught exception 'NSInvalidArgumentException',reason: '-[NSURL tracksWithMediaType:]:

这是代码：

AVMutableComposition *mixComposition = [AVMutableComposition composition];
AVMutableCompositionTrack *compositionTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
NSError * error = nil;
NSMutableArray * timeRanges = [NSMutableArray arrayWithCapacity:videoClipPaths.count];
NSMutableArray * tracks = [NSMutableArray arrayWithCapacity:videoClipPaths.count];
for (int i=0; i<[videoClipPaths count]; i++) {
    AVURLAsset *assetClip = [videoClipPaths objectAtIndex:i];
    AVAssetTrack *clipVideoTrackB = [[assetClip tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

    [timeRanges addObject:[NSValue valueWithCMTimeRange:CMTimeRangeMake(kCMTimeZero,assetClip.duration)]];
    [tracks addObject:clipVideoTrackB];
}
[compositionTrack insertTimeRanges:timeRanges ofTracks:tracks atTime:kCMTimeZero error:&error];

AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPreset1280x720];
NSParameterAssert(exporter != nil);
NSArray *t;
NSString *u;

t = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES);
u = [t objectAtIndex:0];
NSString *finalPath = [u stringByAppendingPathComponent:@"final.mov"];
NSURL *lastURL = [NSURL fileURLWithPath:finalPath];
exporter.outputFileType = AVFileTypeQuickTimeMovie;
exporter.outputURL = lastURL;
[exporter exportAsynchronouslyWithCompletionHandler:^(void){
    switch (exporter.status) {
        case AVAssetExportSessionStatusFailed:
            NSLog(@"exporting failed");
            break;
        case AVAssetExportSessionStatusCompleted:
            NSLog(@"exporting completed");
            //UISaveVideoAtPathToSavedPhotosAlbum(filePath,self,nil,NULL);
            break;
        case AVAssetExportSessionStatusCancelled:
            NSLog(@"export cancelled");
            break;
    }
}];