iOS AVFoundation音频/视频不同步

问题：

+(AVMutableComposition*)overlayAudio:(AVURLAsset*)audioAsset
                          withVideo:(AVURLAsset*)videoAsset
{
    AVMutableComposition* mixComposition = [AVMutableComposition composition];

    AVAssetTrack* audioTrack = [self getTrackFromAsset:audioAsset withMediaType:AVMediaTypeAudio];
    AVAssetTrack* videoTrack = [self getTrackFromAsset:videoAsset withMediaType:AVMediaTypeVideo];
    CMTime duration = videoTrack.timeRange.duration;

    AVMutableCompositionTrack* audioComposition = [self composeTrack:audioTrack withComposition:mixComposition andDuration:duration andMedia:AVMediaTypeAudio];
    AVMutableCompositionTrack* videoComposition = [self composeTrack:videoTrack withComposition:mixComposition andDuration:duration andMedia:AVMediaTypeVideo];
    [self makeAssertionAgainstAudio:audioComposition andVideo:videoComposition];
    return mixComposition;
}

+(AVAssetTrack*)getTrackFromAsset:(AVURLAsset*)asset withMediaType:(NSString*)mediaType
{
    return [[asset tracksWithMediaType:mediaType] objectAtIndex:0];
}

+(AVAssetExportSession*)configureExportSessionWithAsset:(AVMutableComposition*)composition toUrl:(NSURL*)url
{
    AVAssetExportSession* exportSession = [[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetHighestQuality];
    exportSession.outputFileType = @"com.apple.quicktime-movie";
    exportSession.outputURL = url;
    exportSession.shouldOptimizeForNetworkUse = YES;

    return exportSession;
}

-(IBAction)playVideo
{
    [avPlayer pause];
    avPlayerItem = [AVPlayerItem playerItemWithAsset:mixComposition];
    avPlayer = [[AVPlayer alloc]initWithPlayerItem:avPlayerItem];

    avPlayerLayer =[AVPlayerLayer playerLayerWithPlayer:avPlayer];
    [avPlayerLayer setFrame:CGRectMake(0, 0, 305, 283)];
    [avPlayerLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
    [playerView.layer addSublayer:avPlayerLayer];

    [avPlayer seekToTime:kCMTimeZero];
    [avPlayer play];
}

在每次播放过程中，音频比视频慢1-2秒

---

设置：

+(AVMutableComposition*)overlayAudio:(AVURLAsset*)audioAsset
                          withVideo:(AVURLAsset*)videoAsset
{
    AVMutableComposition* mixComposition = [AVMutableComposition composition];

    AVAssetTrack* audioTrack = [self getTrackFromAsset:audioAsset withMediaType:AVMediaTypeAudio];
    AVAssetTrack* videoTrack = [self getTrackFromAsset:videoAsset withMediaType:AVMediaTypeVideo];
    CMTime duration = videoTrack.timeRange.duration;

    AVMutableCompositionTrack* audioComposition = [self composeTrack:audioTrack withComposition:mixComposition andDuration:duration andMedia:AVMediaTypeAudio];
    AVMutableCompositionTrack* videoComposition = [self composeTrack:videoTrack withComposition:mixComposition andDuration:duration andMedia:AVMediaTypeVideo];
    [self makeAssertionAgainstAudio:audioComposition andVideo:videoComposition];
    return mixComposition;
}

+(AVAssetTrack*)getTrackFromAsset:(AVURLAsset*)asset withMediaType:(NSString*)mediaType
{
    return [[asset tracksWithMediaType:mediaType] objectAtIndex:0];
}

+(AVAssetExportSession*)configureExportSessionWithAsset:(AVMutableComposition*)composition toUrl:(NSURL*)url
{
    AVAssetExportSession* exportSession = [[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetHighestQuality];
    exportSession.outputFileType = @"com.apple.quicktime-movie";
    exportSession.outputURL = url;
    exportSession.shouldOptimizeForNetworkUse = YES;

    return exportSession;
}

-(IBAction)playVideo
{
    [avPlayer pause];
    avPlayerItem = [AVPlayerItem playerItemWithAsset:mixComposition];
    avPlayer = [[AVPlayer alloc]initWithPlayerItem:avPlayerItem];

    avPlayerLayer =[AVPlayerLayer playerLayerWithPlayer:avPlayer];
    [avPlayerLayer setFrame:CGRectMake(0, 0, 305, 283)];
    [avPlayerLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
    [playerView.layer addSublayer:avPlayerLayer];

    [avPlayer seekToTime:kCMTimeZero];
    [avPlayer play];
}

这些资产从媒体流中加载AVURLSets

为了写这篇文章，我使用了AVMutableCompositions和AVMutableCompositionTracks，它们的时间尺度是不对称的。音频和视频都通过流传输到设备。音频的时间刻度为44100；视频的时间刻度是600

播放是用AVPlayer完成的

---

尝试的解决方案：

+(AVMutableComposition*)overlayAudio:(AVURLAsset*)audioAsset
                          withVideo:(AVURLAsset*)videoAsset
{
    AVMutableComposition* mixComposition = [AVMutableComposition composition];

    AVAssetTrack* audioTrack = [self getTrackFromAsset:audioAsset withMediaType:AVMediaTypeAudio];
    AVAssetTrack* videoTrack = [self getTrackFromAsset:videoAsset withMediaType:AVMediaTypeVideo];
    CMTime duration = videoTrack.timeRange.duration;

    AVMutableCompositionTrack* audioComposition = [self composeTrack:audioTrack withComposition:mixComposition andDuration:duration andMedia:AVMediaTypeAudio];
    AVMutableCompositionTrack* videoComposition = [self composeTrack:videoTrack withComposition:mixComposition andDuration:duration andMedia:AVMediaTypeVideo];
    [self makeAssertionAgainstAudio:audioComposition andVideo:videoComposition];
    return mixComposition;
}

+(AVAssetTrack*)getTrackFromAsset:(AVURLAsset*)asset withMediaType:(NSString*)mediaType
{
    return [[asset tracksWithMediaType:mediaType] objectAtIndex:0];
}

+(AVAssetExportSession*)configureExportSessionWithAsset:(AVMutableComposition*)composition toUrl:(NSURL*)url
{
    AVAssetExportSession* exportSession = [[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetHighestQuality];
    exportSession.outputFileType = @"com.apple.quicktime-movie";
    exportSession.outputURL = url;
    exportSession.shouldOptimizeForNetworkUse = YES;

    return exportSession;
}

-(IBAction)playVideo
{
    [avPlayer pause];
    avPlayerItem = [AVPlayerItem playerItemWithAsset:mixComposition];
    avPlayer = [[AVPlayer alloc]initWithPlayerItem:avPlayerItem];

    avPlayerLayer =[AVPlayerLayer playerLayerWithPlayer:avPlayer];
    [avPlayerLayer setFrame:CGRectMake(0, 0, 305, 283)];
    [avPlayerLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
    [playerView.layer addSublayer:avPlayerLayer];

    [avPlayer seekToTime:kCMTimeZero];
    [avPlayer play];
}

• 使用

  videoAssetTrack.timeRange

  进行

  [合成插入时间范围]

• 使用

  CMTimeRangeMake（kCMTimeZero，videoAssetTrack.duration）

• 使用

  CMTimeRangeMake（kCMTimeZero，videoAssetTrack.timeRange.duration）

---

代码：

+(AVMutableComposition*)overlayAudio:(AVURLAsset*)audioAsset
                          withVideo:(AVURLAsset*)videoAsset
{
    AVMutableComposition* mixComposition = [AVMutableComposition composition];

    AVAssetTrack* audioTrack = [self getTrackFromAsset:audioAsset withMediaType:AVMediaTypeAudio];
    AVAssetTrack* videoTrack = [self getTrackFromAsset:videoAsset withMediaType:AVMediaTypeVideo];
    CMTime duration = videoTrack.timeRange.duration;

    AVMutableCompositionTrack* audioComposition = [self composeTrack:audioTrack withComposition:mixComposition andDuration:duration andMedia:AVMediaTypeAudio];
    AVMutableCompositionTrack* videoComposition = [self composeTrack:videoTrack withComposition:mixComposition andDuration:duration andMedia:AVMediaTypeVideo];
    [self makeAssertionAgainstAudio:audioComposition andVideo:videoComposition];
    return mixComposition;
}

+(AVAssetTrack*)getTrackFromAsset:(AVURLAsset*)asset withMediaType:(NSString*)mediaType
{
    return [[asset tracksWithMediaType:mediaType] objectAtIndex:0];
}

+(AVAssetExportSession*)configureExportSessionWithAsset:(AVMutableComposition*)composition toUrl:(NSURL*)url
{
    AVAssetExportSession* exportSession = [[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetHighestQuality];
    exportSession.outputFileType = @"com.apple.quicktime-movie";
    exportSession.outputURL = url;
    exportSession.shouldOptimizeForNetworkUse = YES;

    return exportSession;
}

-(IBAction)playVideo
{
    [avPlayer pause];
    avPlayerItem = [AVPlayerItem playerItemWithAsset:mixComposition];
    avPlayer = [[AVPlayer alloc]initWithPlayerItem:avPlayerItem];

    avPlayerLayer =[AVPlayerLayer playerLayerWithPlayer:avPlayer];
    [avPlayerLayer setFrame:CGRectMake(0, 0, 305, 283)];
    [avPlayerLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
    [playerView.layer addSublayer:avPlayerLayer];

    [avPlayer seekToTime:kCMTimeZero];
    [avPlayer play];
}

---

评论：

+(AVMutableComposition*)overlayAudio:(AVURLAsset*)audioAsset
                          withVideo:(AVURLAsset*)videoAsset
{
    AVMutableComposition* mixComposition = [AVMutableComposition composition];

    AVAssetTrack* audioTrack = [self getTrackFromAsset:audioAsset withMediaType:AVMediaTypeAudio];
    AVAssetTrack* videoTrack = [self getTrackFromAsset:videoAsset withMediaType:AVMediaTypeVideo];
    CMTime duration = videoTrack.timeRange.duration;

    AVMutableCompositionTrack* audioComposition = [self composeTrack:audioTrack withComposition:mixComposition andDuration:duration andMedia:AVMediaTypeAudio];
    AVMutableCompositionTrack* videoComposition = [self composeTrack:videoTrack withComposition:mixComposition andDuration:duration andMedia:AVMediaTypeVideo];
    [self makeAssertionAgainstAudio:audioComposition andVideo:videoComposition];
    return mixComposition;
}

+(AVAssetTrack*)getTrackFromAsset:(AVURLAsset*)asset withMediaType:(NSString*)mediaType
{
    return [[asset tracksWithMediaType:mediaType] objectAtIndex:0];
}

+(AVAssetExportSession*)configureExportSessionWithAsset:(AVMutableComposition*)composition toUrl:(NSURL*)url
{
    AVAssetExportSession* exportSession = [[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetHighestQuality];
    exportSession.outputFileType = @"com.apple.quicktime-movie";
    exportSession.outputURL = url;
    exportSession.shouldOptimizeForNetworkUse = YES;

    return exportSession;
}

-(IBAction)playVideo
{
    [avPlayer pause];
    avPlayerItem = [AVPlayerItem playerItemWithAsset:mixComposition];
    avPlayer = [[AVPlayer alloc]initWithPlayerItem:avPlayerItem];

    avPlayerLayer =[AVPlayerLayer playerLayerWithPlayer:avPlayer];
    [avPlayerLayer setFrame:CGRectMake(0, 0, 305, 283)];
    [avPlayerLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
    [playerView.layer addSublayer:avPlayerLayer];

    [avPlayer seekToTime:kCMTimeZero];
    [avPlayer play];
}

我不太了解AVFoundation框架。很可能我只是误用了我提供的片段。（也就是说，为什么要将“insertTimeRange”用于合成？）

---

我可以提供解决方案所需的任何其他信息，包括调试资产跟踪属性值、网络遥测、流式传输信息等。

如果一致，则似乎存在强制延迟以正确采样音频。 苹果的指南通常比随附的书更容易阅读，但这里是关于延迟的具体说明

---

编程指南将详细说明为什么/什么。

您曾经解决过这个问题吗？我也看到了同样的问题。我的光盘上有一个音频曲目和一个视频曲目，我需要同步播放，但如果我进行任何搜索，它们会一直不同步。真烦人。当视频和音频曲目没有被严重压缩时，效果非常好。你解决过这个问题吗？我也有同样的问题