AVAsset" tracksWithMediaType"返回一个空数组 [英] AVAsset "tracksWithMediaType" returns an empty array

问题描述

这是我用来合并视频的方法的开始

These is the beginning o a method I am using to merge videos together

-(void) mergeVideosAndAudio:(AVAsset *)audioAsset{

    //Load Video Assets

    NSError *error;
    NSArray *dirFiles;
    if ((dirFiles = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:[self documentsDirectory] error:&error]) == nil) {
        // handle the error
    };
    // find all the temp files
    NSArray *movFiles = [dirFiles filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"self BEGINSWITH 'temp'"]];
    NSLog(@"The are %i temp files",movFiles.count);

    //Create assets array
    NSMutableArray *assets = [[NSMutableArray alloc]init];

    for (int i = 0; i < movFiles.count; i++) {
        NSString *videoURL = [[self documentsDirectory] stringByAppendingPathComponent:
                              [NSString stringWithFormat:@"temp%i.mov", i]];

        NSURL *url = [NSURL fileURLWithPath:videoURL];

        AVURLAsset *videoAsset = [AVURLAsset URLAssetWithURL:url options:nil];
        [assets addObject:videoAsset];

    }
        NSLog(@"assets:%i ", assets.count);
    // a second way
    for (id obj in assets)
        NSLog(@"obj: %@", obj);

    //Create the composition
    AVMutableComposition *mixComposition = [[AVMutableComposition alloc] init];

    // 1 - Video track
    AVMutableCompositionTrack *firstTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo
                                                                        preferredTrackID:kCMPersistentTrackID_Invalid];
    CMTime videoTrackDuration;
    for (int j = 0; j < assets.count; j++) {
        AVURLAsset *currentAsset = assets[j];
        videoTrackDuration = CMTimeAdd(videoTrackDuration, currentAsset.duration);
        CMTime time;
        if (j == 0) {
            time = kCMTimeZero;

        }else{
            AVURLAsset *previousAsset = assets[j-1];
            time = previousAsset.duration;
        }

        AVAssetTrack *assetTrack = [[currentAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

        [firstTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, currentAsset.duration) ofTrack:assetTrack atTime:time error:nil];
    }

我遇到的问题是 tracksWithMediaType currentAsset的属性是一个空数组。
这是控制台

The problem I am having is that the tracksWithMediaType property of currentAsset is an empty array. Here is the console

任何帮助将不胜感激。
谢谢

Any help will be greatly appreciated. Thanks

推荐答案

你见过这个链接？

我正在研究解决方案KVO的轨道键：

I'm working on a solution now that KVO's the tracks key:

[item addObserver:self forKeyPath:kTracksKey options:opts context:nil];

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