ios 视频拼接/合成

上面的图说明的是这个混合的过程，下面放代码：

- (void)mergeAndExportVideos:(NSArray*)videosPathArray withOutPath:(NSString*)outpath{
    if (videosPathArray.count == 0) {
        return;
    }
    AVMutableComposition *mixComposition = [[AVMutableComposition alloc] init];

    AVMutableCompositionTrack *audioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio
                    preferredTrackID:kCMPersistentTrackID_Invalid];
    AVMutableCompositionTrack *videoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo
                    preferredTrackID:kCMPersistentTrackID_Invalid];
    CMTime totalDuration = kCMTimeZero;
    for (int i = 0; i < videosPathArray.count; i++) {
        AVURLAsset *asset = [AVURLAsset assetWithURL:[NSURL fileURLWithPath:videosPathArray[i]]];
        NSError *erroraudio = nil;　　　　　//获取AVAsset中的音频 或者视频
        AVAssetTrack *assetAudioTrack = [[asset tracksWithMediaType:AVMediaTypeAudio] firstObject];　　　　　//向通道内加入音频或者视频
        BOOL ba = [audioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration)
                            ofTrack:assetAudioTrack
                             atTime:totalDuration
                              error:&erroraudio];

        NSLog(@"erroraudio:%@%d",erroraudio,ba);
        NSError *errorVideo = nil;
        AVAssetTrack *assetVideoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo]firstObject];
       BOOL bl = [videoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration)
                            ofTrack:assetVideoTrack
                             atTime:totalDuration
                              error:&errorVideo];

        NSLog(@"errorVideo:%@%d",errorVideo,bl);
        totalDuration = CMTimeAdd(totalDuration, asset.duration);
    }
    NSLog(@"%@",NSHomeDirectory());

        NSURL *mergeFileURL = [NSURL fileURLWithPath:outpath];
    AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:mixComposition
                                                                      presetName:AVAssetExportPreset640x480];
    exporter.outputURL = mergeFileURL;
    exporter.outputFileType = AVFileTypeMPEG4;
    exporter.shouldOptimizeForNetworkUse = YES;
    [exporter exportAsynchronouslyWithCompletionHandler:^{
        NSLog(@"exporter%@",exporter.error);
    }];

下面是方法详解：

- (AVMutableCompositionTrack *)addMutableTrackWithMediaType:(NSString *)mediaType preferredTrackID:(CMPersistentTrackID)preferredTrackID;

参数：

mediaType          ：数据类型  AVMediaTypeVideo 视频   AVMediaTypeAudio  音频

preferredTrackID ：可自由设定 但建议kCMPersistentTrackID_Invalid也就是0

//向通道内加入音频或者视频
- (BOOL)insertTimeRange:(CMTimeRange)timeRange ofTrack:(AVAssetTrack *)track atTime:(CMTime)startTime error:(NSError * __nullable * __nullable)outError;

参数：

timeRange:  插入视频/音频的的时间段

track        ：插入的视频/音频