具有一个视频轨道和多个音频轨道的 AVPlayer

我试图让我的应用程序中的播放器能够拥有一个视频轨道和多个音频轨道（针对不同的语言）。

我已经这样做了，但播放器无法启动：

AVMutableComposition *composition = [AVMutableComposition composition];
AVURLAsset* videoAsset = [[AVURLAsset alloc]initWithURL:urlVideo options:nil];

AVMutableCompositionTrack *compositionVideoTrack = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
NSError* error = NULL;

[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero,videoAsset.duration) 
                               ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo]objectAtIndex:0] 
                                atTime:kCMTimeZero
                                 error:&error];

NSMutableArray *allAudio = [[NSMutableArray alloc]init];
for (int i=1; i < [allAudioTracks count]; i++) {
    NSURL *audioURL = [NSURL URLWithString:[NSString stringWithFormat:@"%@%@",URL_MEDIA,[[allAudioTracks objectAtIndex:i]audio]]];
    AVURLAsset* audioAsset = [[AVURLAsset alloc]initWithURL:audioURL options:nil];
    [allAudio addObject:audioAsset];
    [audioAsset release];
    [audioURL release];
}

for (int i=0; i < [allAudio count]; i++) {
    NSError* error = NULL;
    AVURLAsset *audioAsset = (AVURLAsset*)[allAudio objectAtIndex:i];
    //audioAsset = [allAudio objectAtIndex:i];

    AVMutableCompositionTrack *compositionAudioTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
    [compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero,audioAsset.duration) 
                                    ofTrack:[[audioAsset tracksWithMediaType:AVMediaTypeAudio]objectAtIndex:0]
                                     atTime:kCMTimeZero
                                      error:&error];

    NSLog(@"Error : %@", error);
    //[allCompositionTrack addObject:compositionAudioTrack];
    [audioAsset release];
}

我尝试像这样启动我的播放器：

AVPlayerItem *playerItem = [[AVPlayerItem alloc]initWithAsset:composition];

player = [[AVPlayer alloc]initWithPlayerItem:playerItem];

layerVideo = [AVPlayerLayer playerLayerWithPlayer:player];
layerVideo.frame = CGRectMake(0, 0, 480, 320);
[self.view.layer addSublayer:layerVideo];

[player play];

但没有任何附加。 感谢您的帮助（对我的英语感到抱歉:)）

我认为这一行：

NSURL *audioURL = [NSURL URLWithString:[NSString stringWithFormat:@"%@%@",URL_MEDIA,[[allAudioTracks objectAtIndex:i]audio]]];

如果您使用文件，则必须提交 URLWithString 而不是 URLWithString。常见的错误。让我知道。