ios - AVMutableCompositionTrack setVolume不起作用

Question

将录制的视频和资源中的音频混合时，无法设置音频音量。

这是我的代码:

AVMutableComposition *composition = [[AVMutableComposition alloc] init];
NSString *resourcePath = [[NSBundle mainBundle] pathForResource:@"give-it-away" ofType:@"mp3"];
AVURLAsset *audioAsset = [[AVURLAsset alloc] initWithURL:[NSURL fileURLWithPath:resourcePath] options:[NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES],AVURLAssetPreferPreciseDurationAndTimingKey, nil]];
AVMutableCompositionTrack *videoTrack = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
AVMutableCompositionTrack *audioTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
[videoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration) ofTrack:[videoAsset.tracks objectAtIndex:0] atTime:kCMTimeZero error:nil];
[audioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, audioTime) ofTrack:[audioAsset.tracks objectAtIndex:0] atTime:kCMTimeZero error:&videoError];

AVMutableAudioMixInputParameters *audioInputParams = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:audioTrack] ;
[audioInputParams setVolume:0.3 atTime:kCMTimeZero];
[audioInputParams setTrackID:audioTrack.trackID];
AVMutableAudioMix *audioMix = [AVMutableAudioMix audioMix];
audioMix.inputParameters = [NSArray arrayWithObject:audioInputParams];

AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetPassthrough];

exportSession.outputURL = [NSURL fileURLWithPath:finalVideoWithAudioPath];
exportSession.outputFileType = AVFileTypeQuickTimeMovie;            
exportSession.audioMix = audioMix;            
[exportSession exportAsynchronouslyWithCompletionHandler:^{
      switch (exportSession.status)
      {
          case AVAssetExportSessionStatusFailed:
          {
               [self performSelectorOnMainThread:@selector(doPostExportFailed) withObject:nil waitUntilDone:NO];
               break;
          }
          case AVAssetExportSessionStatusCompleted:
          {
               [self performSelectorOnMainThread:@selector(doPostExportSuccess) withObject:nil waitUntilDone:YES];
               break;
          }
      };
}];

导出成功完成，但是音量不变。
我究竟做错了什么？

谢谢

Answer 1

更新(2018年12月)

这段代码在iOS 12.1.2上对我有用:

- (void) combineAudio:(NSString*)audioPath forRecord:(VideoRecord*)record isResource:(BOOL)isResource isSilent:(BOOL)isSilent keepCurrentAudio:(BOOL)keepCurrentAudio withCompletionHandler:(void (^)(AVAssetExportSession* exportSession, NSString* exportPath))handler {

    NSString *resourcePath = audioPath;
    if (isResource) {
        resourcePath = [[NSBundle mainBundle] pathForResource:resourcePath ofType:@"mp3"];
    }

    NSURL *url = [NSURL fileURLWithPath:resourcePath];

    AVURLAsset* audioAsset = [[AVURLAsset alloc]initWithURL:url options:nil];
    AVURLAsset* videoAsset = [[AVURLAsset alloc]initWithURL:[NSURL URLWithString:[NSString stringWithFormat:@"file://%@",record.videoPath]] options:nil];

    AVMutableComposition *composition = [self getComposition];

    AVMutableCompositionTrack *compositionAudioTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio
                                                                                   preferredTrackID:kCMPersistentTrackID_Invalid];

    AVMutableCompositionTrack *compositionAudioOriginalTrack = nil;

    if (keepCurrentAudio && [videoAsset tracksWithMediaType:AVMediaTypeAudio].count > 0) {
        compositionAudioOriginalTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio
                                                                    preferredTrackID:kCMPersistentTrackID_Invalid];
        [compositionAudioOriginalTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
                                               ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0]
                                                atTime:kCMTimeZero error:nil];
    }

    if (isResource) {
        CMTime videoDuration = videoAsset.duration;
        if(CMTimeCompare(videoDuration, audioAsset.duration) == -1){
            [compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
                                           ofTrack:[[audioAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0]
                                            atTime:kCMTimeZero error:nil];
        } else if(CMTimeCompare(videoDuration, audioAsset.duration) == 1) {
            CMTime currentTime = kCMTimeZero;
            while(YES){
                CMTime audioDuration = audioAsset.duration;
                CMTime totalDuration = CMTimeAdd(currentTime,audioDuration);
                if(CMTimeCompare(totalDuration, videoDuration)==1){
                    audioDuration = CMTimeSubtract(totalDuration,videoDuration);

                }
                [compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, audioDuration)
                                               ofTrack:[[audioAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0]
                                                atTime:currentTime error:nil];

                currentTime = CMTimeAdd(currentTime, audioDuration);
                if(CMTimeCompare(currentTime, videoDuration) == 1 || CMTimeCompare(currentTime, videoDuration) == 0){
                    break;
                }
            }
        }
    } else {
        NSArray<AVAssetTrack *>* aTracks = [audioAsset tracksWithMediaType:AVMediaTypeAudio];
        if (aTracks.count > 0) {
            [compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
                                           ofTrack:[aTracks objectAtIndex:0]
                                            atTime:kCMTimeZero error:nil];
        }

    }

    AVMutableCompositionTrack *compositionVideoTrack = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
    NSArray *tracks = [videoAsset tracksWithMediaType:AVMediaTypeVideo];
    if (tracks.count == 0) {
        CLSNSLog(@"%@ - combineAudio - video tracks zero", NSStringFromClass([self class]));
        // TODO - Handle this error.
        return;
    }
    [compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)
                                   ofTrack:[tracks objectAtIndex:0]
                                    atTime:kCMTimeZero error:nil];

    AVAssetExportSession* _assetExport = [[AVAssetExportSession alloc] initWithAsset:[composition copy]
                                                                          presetName:AVAssetExportPresetHighestQuality];

    NSString *exportPath = [record.videoPath stringByReplacingOccurrencesOfString:@".mp4" withString:@"_audio_added.mp4"];
    if ([record.videoPath containsString:@".MOV"]) {
        exportPath = [record.videoPath stringByReplacingOccurrencesOfString:@".MOV" withString:@"_audio_added.mp4"];
    }
    if ([record.videoPath containsString:@".mov"]) {
        exportPath = [record.videoPath stringByReplacingOccurrencesOfString:@".mov" withString:@"_audio_added.mp4"];
    }
    NSURL    *exportUrl = [NSURL fileURLWithPath:exportPath];

    if ([[NSFileManager defaultManager] fileExistsAtPath:exportPath]) {
        [[NSFileManager defaultManager] removeItemAtPath:exportPath error:nil];
    }

    AVMutableAudioMix *audioMix = [AVMutableAudioMix audioMix];

    float volume = .5f;
    if (keepCurrentAudio) {
        volume = .6f;
    }

    AVMutableAudioMixInputParameters *audioInputParams = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:compositionAudioTrack] ;
    [audioInputParams setVolumeRampFromStartVolume:(isSilent ? .0f : volume) toEndVolume:(isSilent ? .0f : volume) timeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)];
    [audioInputParams setTrackID:compositionAudioTrack.trackID];

    NSArray *inputParams = [NSArray arrayWithObject:audioInputParams];

    AVMutableAudioMixInputParameters *audioOriginalInputParams = nil;
    if (keepCurrentAudio) {
        audioOriginalInputParams = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:compositionAudioOriginalTrack] ;
        [audioInputParams setVolumeRampFromStartVolume:(isSilent ? .0f : .06f) toEndVolume:(isSilent ? .0f : .06f) timeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)];
        [audioInputParams setTrackID:compositionAudioOriginalTrack.trackID];

        inputParams = [NSArray arrayWithObjects:audioInputParams, audioOriginalInputParams, nil];
    }

    audioMix.inputParameters = inputParams;

    _assetExport.outputFileType = AVFileTypeQuickTimeMovie;
    _assetExport.audioMix = audioMix;
    _assetExport.outputURL = exportUrl;
    _assetExport.shouldOptimizeForNetworkUse = YES;

    [_assetExport exportAsynchronouslyWithCompletionHandler:^{
        handler(_assetExport, exportPath);

    }];
}

我这样称呼此函数(声音是资源文件的名称):

[[FBVideoEditor shared] combineAudio:sound forRecord:self.record isResource:YES isSilent:NO withCompletionHandler:^(AVAssetExportSession *exportSession, NSString *exportPath) {
    switch (exportSession.status)
    {
        case AVAssetExportSessionStatusCancelled:
            CLSNSLog(@"AVAssetExportSessionStatusCancelled");
            break;
        case AVAssetExportSessionStatusExporting:
            CLSNSLog(@"AVAssetExportSessionStatusExporting");
            break;
        case AVAssetExportSessionStatusUnknown:
            CLSNSLog(@"AVAssetExportSessionStatusUnknown");
            break;
        case AVAssetExportSessionStatusWaiting:
            CLSNSLog(@"AVAssetExportSessionStatusWaiting");
            break;
        case AVAssetExportSessionStatusFailed:
        {
            CLSNSLog(@"Export Failed with error messsage: %@", exportSession.error.userInfo );
            break;
        }
        case AVAssetExportSessionStatusCompleted:
        {
            // Success
        }
    };
}];

VideoRecord类包含我的视频的所有必要数据。但是在这种情况下，它仅使用视频路径，因此您可以将其更改为简单的NSString。

希望能帮助到你。