相关疑难解决方法(0)

我正在尝试使用AVMutableComposition在精确的时间播放一系列声音文件.

当视图加载时,我创建合成,目的是在1秒内均匀地播放4个声音.声音的长短不应该无关紧要,我只想在0,0.25,0.5和0.75秒时将它们发射:

AVMutableComposition *composition = [[AVMutableComposition alloc] init];
NSDictionary *options = @{AVURLAssetPreferPreciseDurationAndTimingKey : @YES};

for (NSInteger i = 0; i < 4; i++)
{
  AVMutableCompositionTrack* track = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
  NSURL *url = [[NSBundle mainBundle] URLForResource:[NSString stringWithFormat:@"sound_file_%i", i] withExtension:@"caf"];
  AVURLAsset *asset = [AVURLAsset URLAssetWithURL:url options:options];
  AVAssetTrack *assetTrack = [asset tracksWithMediaType:AVMediaTypeAudio].firstObject;
  CMTimeRange timeRange = [assetTrack timeRange];
  Float64 t = i * 0.25;
  NSError *error;
  BOOL success = [track insertTimeRange:timeRange ofTrack:assetTrack atTime:CMTimeMakeWithSeconds(t, 1) error:&error];
  if (!success)
  {
    NSLog(@"unsuccesful creation of composition");
  } …