Iphone 将AVURLAsset的音频传输切换到多个audio类型的AvassetTrack

我有一个AVURLAsset，有多个音频类型的AvassetTrack。我想能够允许用户通过触摸按钮在这些不同的音频曲目之间切换。可以打开和关闭第一首曲目的音量，但当音量设置为1.0时，不会听到其他曲目的声音

下面是调整曲目音量的代码（sender是一个UIButton，标签设置为audioTracks中资产的索引）

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我需要做些什么才能使所需的曲目成为活动曲目吗？

确定发现问题。与上述代码无关，因为这可以正常工作。问题是未启用除第一首曲目以外的音频Avassettrack。要启用此功能，必须使用AVMutableComposition重新创建资产：

NSURL *fileURL = [[NSBundle mainBundle]
                  URLForResource:@"movie" withExtension:@"mp4"];

AVURLAsset *asset = [AVURLAsset URLAssetWithURL:fileURL options:nil];

AVMutableComposition *composition = [AVMutableComposition composition];

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

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

NSArray *allAudio = [asset tracksWithMediaType:AVMediaTypeAudio];
for (int i=0; i < [allAudio count]; i++) {
    NSError* error = NULL;
    AVAssetTrack *audioAsset = (AVAssetTrack*)[allAudio objectAtIndex:i];

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

    NSLog(@"Error : %@", error);

}

NSURL*fileURL=[[NSBundle mainBundle]
URLForResource:@“movie”带扩展名：@“mp4”]；
AVURLAsset*asset=[AVURLAsset URLAssetWithURL:fileURL选项：nil]；
AVMutableComposition*composition=[AVMutableComposition]；
AVMutableCompositionTrack*compositionVideoTrack=[composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_无效]；
n错误*错误=NULL；
[compositionVideoTrack insertTimeRange:CMTimeRangeMake（kCMTimeZero，asset.duration）
ofTrack:[[asset tracksWithMediaType:AVMediaTypeVideo]对象索引：0]
时间：kCMTimeZero
错误：&错误]；
NSArray*allAudio=[asset tracksWithMediaType:AVMediaTypeAudio]；
对于（int i=0；i<[allAudio count]；i++）{
n错误*错误=NULL；
AVAssetTrack*audioAsset=（AVAssetTrack*）[allAudio objectAtIndex:i]；
AVMutableCompositionTrack*compositionAudioTrack=[CompositionAddMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_无效]；
[compositionAudioTrack insertTimeRange:CMTimeRangeMake（kCMTimeZero，asset.duration）
ofTrack:audioAsset
时间：kCMTimeZero
错误：&错误]；
NSLog（@“错误：%@”，错误）；
}

非常感谢！这帮了大忙！谢谢,谢谢,谢谢!！这非常有用！

NSURL *fileURL = [[NSBundle mainBundle]
                  URLForResource:@"movie" withExtension:@"mp4"];

AVURLAsset *asset = [AVURLAsset URLAssetWithURL:fileURL options:nil];

AVMutableComposition *composition = [AVMutableComposition composition];

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

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

NSArray *allAudio = [asset tracksWithMediaType:AVMediaTypeAudio];
for (int i=0; i < [allAudio count]; i++) {
    NSError* error = NULL;
    AVAssetTrack *audioAsset = (AVAssetTrack*)[allAudio objectAtIndex:i];

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

    NSLog(@"Error : %@", error);

}