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 == ) {
        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 = ; 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

补充调整视频方向的方法，个人感觉不是很好，希望大家给点建议： 从stackoverflow查到的具体网址忘了

代码如下：

- (void)startExportVideoWithVideoAsset:(AVURLAsset *)videoAsset completion:(void (^)(NSString *outputPath))completion {

    AVAssetExportSession *session = [[AVAssetExportSession alloc]initWithAsset:videoAsset presetName:AVAssetExportPresetHighestQuality];
    //
    AVMutableVideoComposition *videoComposition = [self fixedCompositionWithAsset:videoAsset];
    if (videoComposition.renderSize.width) {
        // 修正视频转向
        session.videoComposition = videoComposition;
    }
    //
    NSDateFormatter *formater = [[NSDateFormatter alloc] init];
    [formater setDateFormat:@"yyyy-MM-dd-HH:mm:ss"];
    NSString *outputPath = [NSHomeDirectory() stringByAppendingFormat:@"/tmp/output-%@.mp4", [formater stringFromDate:[NSDate date]]];
    session.outputURL = [NSURL fileURLWithPath:outputPath];
    
    // Optimize for network use.
    session.shouldOptimizeForNetworkUse = true;
    
    NSArray *supportedTypeArray = session.supportedFileTypes;
    if ([supportedTypeArray containsObject:AVFileTypeMPEG4]) {
        session.outputFileType = AVFileTypeMPEG4;
    } else if (supportedTypeArray.count == 0) {
        NSLog(@"No supported file types 视频类型暂不支持导出");
        return;
    } else {
        session.outputFileType = [supportedTypeArray firstObject];
    }
    
    if (![[NSFileManager defaultManager] fileExistsAtPath:[NSHomeDirectory() stringByAppendingFormat:@"/tmp"]]) {
        [[NSFileManager defaultManager] createDirectoryAtPath:[NSHomeDirectory() stringByAppendingFormat:@"/tmp"] withIntermediateDirectories:YES attributes:nil error:nil];
    }
    // Begin to export video to the output path asynchronously.
    [session exportAsynchronouslyWithCompletionHandler:^(void) {
        NSLog(@"%@",[session.error description]);
        switch (session.status) {
            case AVAssetExportSessionStatusUnknown:
                NSLog(@"AVAssetExportSessionStatusUnknown"); break;
            case AVAssetExportSessionStatusWaiting:
                NSLog(@"AVAssetExportSessionStatusWaiting"); break;
            case AVAssetExportSessionStatusExporting:
                NSLog(@"AVAssetExportSessionStatusExporting"); break;
            case AVAssetExportSessionStatusCompleted: {
                NSLog(@"AVAssetExportSessionStatusCompleted");
                dispatch_async(dispatch_get_main_queue(), ^{
                    if (completion) {
                        completion(outputPath);
                    }
                });
            }  break;
            case AVAssetExportSessionStatusFailed:{
                dispatch_async(dispatch_get_main_queue(), ^{
                    if (completion) {
                        completion(nil);
                    }
                });
                NSLog(@"AVAssetExportSessionStatusFailed"); break;
            }
            default: break;
        }
    }];
//    }
}

/// 获取优化后的视频转向信息
- (AVMutableVideoComposition *)fixedCompositionWithAsset:(AVAsset *)videoAsset {
    AVMutableVideoComposition *videoComposition = [AVMutableVideoComposition videoComposition];
    // 视频转向
    int degrees = [self degressFromVideoFileWithAsset:videoAsset];
    if (degrees != 0) {
        CGAffineTransform translateToCenter;
        CGAffineTransform mixedTransform;
        videoComposition.frameDuration = CMTimeMake(1, 30);
        
        NSArray *tracks = [videoAsset tracksWithMediaType:AVMediaTypeVideo];
        AVAssetTrack *videoTrack = [tracks objectAtIndex:0];
        
        if (degrees == 90) {
            // 顺时针旋转90°
            translateToCenter = CGAffineTransformMakeTranslation(videoTrack.naturalSize.height, 0.0);
            mixedTransform = CGAffineTransformRotate(translateToCenter,M_PI_2);
            videoComposition.renderSize = CGSizeMake(videoTrack.naturalSize.height,videoTrack.naturalSize.width);
        } else if(degrees == 180){
            // 顺时针旋转180°
            translateToCenter = CGAffineTransformMakeTranslation(videoTrack.naturalSize.width, videoTrack.naturalSize.height);
            mixedTransform = CGAffineTransformRotate(translateToCenter,M_PI);
            videoComposition.renderSize = CGSizeMake(videoTrack.naturalSize.width,videoTrack.naturalSize.height);
        } else if(degrees == 270){
            // 顺时针旋转270°
            translateToCenter = CGAffineTransformMakeTranslation(0.0, videoTrack.naturalSize.width);
            mixedTransform = CGAffineTransformRotate(translateToCenter,M_PI_2*3.0);
            videoComposition.renderSize = CGSizeMake(videoTrack.naturalSize.height,videoTrack.naturalSize.width);
        }
        
        AVMutableVideoCompositionInstruction *roateInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
        roateInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, [videoAsset duration]);
        AVMutableVideoCompositionLayerInstruction *roateLayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];
        
        [roateLayerInstruction setTransform:mixedTransform atTime:kCMTimeZero];
        
        roateInstruction.layerInstructions = @[roateLayerInstruction];
        // 加入视频方向信息
        videoComposition.instructions = @[roateInstruction];
    }
    return videoComposition;
}
/// 获取视频角度
- (int)degressFromVideoFileWithAsset:(AVAsset *)asset {
    int degress = 0;
    NSArray *tracks = [asset tracksWithMediaType:AVMediaTypeVideo];
    if([tracks count] > 0) {
        AVAssetTrack *videoTrack = [tracks objectAtIndex:0];
        CGAffineTransform t = videoTrack.preferredTransform;
        if(t.a == 0 && t.b == 1.0 && t.c == -1.0 && t.d == 0){
            // Portrait
            degress = 90;
        } else if(t.a == 0 && t.b == -1.0 && t.c == 1.0 && t.d == 0){
            // PortraitUpsideDown
            degress = 270;
        } else if(t.a == 1.0 && t.b == 0 && t.c == 0 && t.d == 1.0){
            // LandscapeRight
            degress = 0;
        } else if(t.a == -1.0 && t.b == 0 && t.c == 0 && t.d == -1.0){
            // LandscapeLeft
            degress = 180;
        }
    }
    return degress;
}