合成视频标准写法

// 获取视频

AVURLAsset* videoAsset = [[AVURLAsset alloc]initWithURL:_videoURL options:nil];

// 视频混合

AVMutableComposition *mixComposition = [AVMutableComposition composition];

// 视频轨道

AVMutableCompositionTrack *compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];

// 音频轨道

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

// 插入视频轨道

[compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, CMTimeMake(videoAsset.duration.value, videoAsset.duration.timescale)) ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] firstObject] atTime:kCMTimeZero error:nil];

//    [compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration) ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] firstObject] atTime:kCMTimeZero error:nil];

// 插入音频轨道

[compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, CMTimeMake(videoAsset.duration.value, videoAsset.duration.timescale)) ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeAudio] firstObject] atTime:kCMTimeZero error:nil];

//    [compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration) ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeAudio] firstObject] atTime:kCMTimeZero error:nil];

for (int i = 0; i < self.audioArray.count; i++) {

    AudioRecordData *data = _audioArray[i];

    NSLog(@"starTime = %f",data.startTime);

    AVURLAsset *audioAsset = [AVURLAsset URLAssetWithURL:[NSURL fileURLWithPath:data.audioPath] options:nil];

    CMTime startTime = CMTimeMakeWithSeconds(data.startTime, audioAsset.duration.timescale);

    compositionAudioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];

    [compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, CMTimeMake(videoAsset.duration.value, videoAsset.duration.timescale)) ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] firstObject] atTime:startTime error:nil];

    [compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, CMTimeMake(audioAsset.duration.value, videoAsset.duration.timescale)) ofTrack:[audioAsset tracksWithMediaType:AVMediaTypeAudio].firstObject atTime:startTime error:nil];

}

//调节音量

AVMutableAudioMix *audioMix = [AVMutableAudioMix audioMix];

AVMutableAudioMixInputParameters *audioInputParams = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:compositionAudioTrack] ;

[audioInputParams setVolumeRampFromStartVolume:self.videoVolume toEndVolume:.0f timeRange:CMTimeRangeMake(kCMTimeZero, CMTimeMake(videoAsset.duration.value, videoAsset.duration.timescale))];

[audioInputParams setTrackID:compositionAudioTrack.trackID];

audioMix.inputParameters = [NSArray arrayWithObject:audioInputParams];

// 配置导出

AVAssetExportSession* _assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPreset1280x720];

// 导出视频的临时保存路径

NSString *exportPath = [NSTemporaryDirectory() stringByAppendingPathComponent:@"tmpMov.mov"];

unlink([exportPath UTF8String]);

NSURL *exportUrl = [NSURL fileURLWithPath:exportPath];

// 导出视频的格式 .MOV

_assetExport.outputFileType = AVFileTypeQuickTimeMovie;

_assetExport.outputURL = exportUrl;

_assetExport.audioMix = audioMix;

_assetExport.shouldOptimizeForNetworkUse = YES;

_assetExport.timeRange = CMTimeRangeMake(kCMTimeZero, CMTimeMake(videoAsset.duration.value, videoAsset.duration.timescale));

// 导出视频

[_assetExport exportAsynchronouslyWithCompletionHandler: ^(void ) {

switch ([_assetExport status]) {

    case AVAssetExportSessionStatusFailed:

        NSLog(@"Export failed: %@", [[_assetExport error] localizedDescription]);

    break;

    case AVAssetExportSessionStatusCancelled:

        NSLog(@"Export canceled");

    break;

    default:

        NSLog(@"NONE");

        dispatch_async(dispatch_get_main_queue(), ^{

            [MBProgressHUD hideHUDForView:self.view animated:YES];

            NSURL *movieUrl = [NSURL URLWithString:exportPath];

            UISaveVideoAtPathToSavedPhotosAlbum([movieUrl relativePath], self,@selector(video:didFinishSavingWithError:contextInfo:), nil);

        });

    break;

    }

}];