我正在开发一个简单的视频编辑应用程序。我想在我的应用程序中添加慢动作。我注意到 AVMutableCompositionTrack 类中有一个 scaleTimeRange 方法,所以我用它来实现我的目的。我发现 scaleTimeRange 在视频轨道上效果很好,但对音轨没有任何影响。这意味着音轨仍以原始速度播放。
以下是我的代码:
CMTime insertionPoint = kCMTimeZero;
double wholeDuration = CMTimeGetSeconds([asset duration]);
double doubleDuration = CMTimeGetSeconds([asset duration])*2.0;
CMTime trimmedDuration = CMTimeMakeWithSeconds(wholeDuration, 600.0);
// Create a new composition
self.mutableComposition = [AVMutableComposition composition];
// Insert video and audio tracks from AVAsset
if(assetVideoTrack != nil) {
AVMutableCompositionTrack *compositionVideoTrack = [self.mutableComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, trimmedDuration) ofTrack:assetVideoTrack atTime:insertionPoint error:&error];
[compositionVideoTrack scaleTimeRange:CMTimeRangeMake(kCMTimeZero, trimmedDuration) toDuration:CMTimeMakeWithSeconds(doubleDuration, 600.0)];
}
if(assetAudioTrack != nil) {
AVMutableCompositionTrack *compositionAudioTrack = [self.mutableComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
[compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, trimmedDuration) ofTrack:assetAudioTrack atTime:insertionPoint error:&error];
[compositionAudioTrack scaleTimeRange:CMTimeRangeMake(kCMTimeZero, trimmedDuration) toDuration:CMTimeMakeWithSeconds(doubleDuration, 600.0)];
}
谁能给我一些关于这个问题的建议?谢谢!