IOS视频编辑功能详解下篇-视频裁剪、视频拼接、音视频的处理

转自:http://www.hudongdong.com/ios/550.html

前言

用代码在简单视频编辑中，主要就是加美颜、水印（贴图）、视频截取、视频拼接、音视频的处理，在美颜中，使用GPUImage即可实现多种滤镜、磨皮美颜的功能，并且可以脸部识别实时美颜等功能，这个有很多成熟的处理方案，所以现在主要说后面的水印（贴图）、视频截取、视频拼接、音视频的处理，在文章结尾会给出一个完整的测试demo，该demo可以操作视频之后保存到系统相册，文章主要说明下注意的点。

上篇讲了视频编辑功能详解上篇-添加水印，本篇就说下视频裁剪、视频拼接、音视频的处理。

原理

正如上篇提到的，因为GPUImage只是对视频进行滤镜处理，并没有涉及到视频轨和音轨的处理，所以在视频的处理裁剪等编辑上面主要还是使用的AVFoundation对视频轨和音轨进行处理。

本篇略长，如果只是使用，可以直接去文章最后下载demo源码，复制使用即可。不过建议看懂源码，这样在视频的移动编辑上面就可以自己随便改了。

一、视频裁剪

完整源码：

//使用gpuimage重新录制一次
-(void)saveVedioPath:(NSURL*)vedioPath WithFileName:(NSString*)fileName andCallBack:(JLXCommonToolVedioCompletionHandler)competion
{self.completionHandler = competion;// 滤镜filter = [[GPUImageAlphaBlendFilter alloc] init];//    //mix即为叠加后的透明度,这里就直接写1.0了[(GPUImageDissolveBlendFilter *)filter setMix:1.0f];// 播放NSURL *sampleURL  = vedioPath;AVAsset *asset = [AVAsset assetWithURL:sampleURL];movieFile = [[GPUImageMovie alloc] initWithAsset:asset];movieFile.runBenchmark = YES;movieFile.playAtActualSpeed = NO;AVAssetTrack *videoAssetTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];UIImageOrientation videoAssetOrientation_  = UIImageOrientationUp;//拍摄的时候视频是否是竖屏拍的BOOL isVideoAssetvertical  = NO;CGAffineTransform videoTransform = videoAssetTrack.preferredTransform;if (videoTransform.a == 0 && videoTransform.b == 1.0 && videoTransform.c == -1.0 && videoTransform.d == 0) {isVideoAssetvertical = YES;videoAssetOrientation_ =  UIImageOrientationUp;//正着拍}if (videoTransform.a == 0 && videoTransform.b == -1.0 && videoTransform.c == 1.0 && videoTransform.d == 0) {//        videoAssetOrientation_ =  UIImageOrientationLeft;isVideoAssetvertical = YES;videoAssetOrientation_ = UIImageOrientationDown;//倒着拍}if (videoTransform.a == 1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == 1.0) {isVideoAssetvertical = NO;videoAssetOrientation_ =  UIImageOrientationLeft;//左边拍的}if (videoTransform.a == -1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == -1.0) {isVideoAssetvertical = NO;videoAssetOrientation_ = UIImageOrientationRight;//右边拍}GPUImageView *filterView = [[GPUImageView alloc] initWithFrame:CGRectMake(0, 0, asset.naturalSize.width, asset.naturalSize.height)];[filterView setTransform:CGAffineTransformMakeRotation(M_PI_2)];UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, asset.naturalSize.width, asset.naturalSize.height)];[view setBackgroundColor:[UIColor clearColor]];GPUImageUIElement *uielement = [[GPUImageUIElement alloc] initWithView:view];NSString *pathToMovie = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"Documents/%@.mp4",fileName]];unlink([pathToMovie UTF8String]);NSURL *movieURL = [NSURL fileURLWithPath:pathToMovie];movieWriter = [[GPUImageMovieWriter alloc] initWithMovieURL:movieURL size:CGSizeMake(asset.naturalSize.width, asset.naturalSize.height)];GPUImageFilter* progressFilter = [[GPUImageFilter alloc] init];[movieFile addTarget:progressFilter];[progressFilter addTarget:filter];[uielement addTarget:filter];movieWriter.shouldPassthroughAudio = YES;if ([[asset tracksWithMediaType:AVMediaTypeAudio] count] > 0){movieFile.audioEncodingTarget = movieWriter;} else {//no audiomovieFile.audioEncodingTarget = nil;}[movieFile enableSynchronizedEncodingUsingMovieWriter:movieWriter];// 显示到界面[filter addTarget:filterView];[filter addTarget:movieWriter];[movieWriter startRecording];[movieFile startProcessing];__weak typeof(self) weakSelf = self;[progressFilter setFrameProcessingCompletionBlock:^(GPUImageOutput *output, CMTime time) {[uielement update];}];[movieWriter setCompletionBlock:^{__strong typeof(self) strongSelf = weakSelf;[strongSelf->filter removeTarget:strongSelf->movieWriter];[strongSelf->movieWriter finishRecording];if (strongSelf.completionHandler) {strongSelf.completionHandler(movieURL,nil,isVideoAssetvertical);}}];
}/**裁剪视频@param videoPath 视频的路径@param startTime 截取视频开始时间@param endTime 截取视频结束时间，如果为0则为整个视频@param videoSize 视频截取的大小，如果为0则不裁剪视频大小@param videoDealPoint Point(x,y):传zero则为裁剪从0,0开始@param fileName 文件名字@param shouldScale 是否拉伸，false的话不拉伸，裁剪黑背景*/
- (void)saveVideoPath:(NSURL*)videoPath withStartTime:(float)startTime withEndTime:(float)endTime withSize:(CGSize)videoSize withVideoDealPoint:(CGPoint)videoDealPoint WithFileName:(NSString*)fileName shouldScale:(BOOL)shouldScale
{if (!videoPath) {[SVProgressHUD dismiss];return;}[SVProgressHUD showWithStatus:@"裁剪视频到系统相册"];//1 创建AVAsset实例 AVAsset包含了video的所有信息 self.videoUrl输入视频的路径//封面图片NSDictionary *opts = [NSDictionary dictionaryWithObject:@(YES) forKey:AVURLAssetPreferPreciseDurationAndTimingKey];videoAsset = [AVURLAsset URLAssetWithURL:videoPath options:opts];     //初始化视频媒体文件bool isWXVideo = false;for (int i=0; i<videoAsset.metadata.count; i++) {AVMetadataItem * item = [videoAsset.metadata objectAtIndex:i];NSLog(@"======metadata:%@,%@,%@,%@",item.identifier,item.extraAttributes,item.value,item.dataType);NSDictionary *dic = [self StrToArrayOrNSDictionary:[NSString stringWithFormat:@"%@",item.value]];if ([[dic.allKeys objectAtIndex:0] isEqualToString: @"WXVer"]) {isWXVideo = true;[self saveVedioPath:videoPath WithFileName:@"wxVideo" andCallBack:^(NSURL *assetURL, NSError *error,BOOL isVideoAssetvertical) {dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{NSString *newVideoPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/wxVideo.mp4"];[self goSaveVideoPath:[NSURL fileURLWithPath:newVideoPath] withStartTime:startTime withEndTime:endTime withSize:videoSize withVideoDealPoint:videoDealPoint WithFileName:fileName shouldScale:shouldScale isWxVideoAssetvertical:isVideoAssetvertical];});}];break;}}if ([[videoAsset tracksWithMediaType:AVMediaTypeAudio] count] == 0){[self saveVedioPath:videoPath WithFileName:@"wxVideo" andCallBack:^(NSURL *assetURL, NSError *error,BOOL isVideoAssetvertical) {dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{NSString *newVideoPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/wxVideo.mp4"];[self goSaveVideoPath:[NSURL fileURLWithPath:newVideoPath] withStartTime:startTime withEndTime:endTime withSize:videoSize withVideoDealPoint:videoDealPoint WithFileName:fileName shouldScale:shouldScale isWxVideoAssetvertical:isVideoAssetvertical];});}];return;}if (!isWXVideo) {[self goSaveVideoPath:videoPath withStartTime:startTime withEndTime:endTime withSize:videoSize withVideoDealPoint:videoDealPoint WithFileName:fileName shouldScale:shouldScale isWxVideoAssetvertical:NO];}
}//Assetvertical gpuimage会把微信的竖屏渲染成横屏，横屏还是横屏
- (void)goSaveVideoPath:(NSURL*)videoPath withStartTime:(float)startTime withEndTime:(float)endTime withSize:(CGSize)videoSize withVideoDealPoint:(CGPoint)videoDealPoint WithFileName:(NSString*)fileName shouldScale:(BOOL)shouldScale isWxVideoAssetvertical:(BOOL)Assetvertical{if (!videoPath) {[SVProgressHUD dismiss];return;}//1 创建AVAsset实例 AVAsset包含了video的所有信息 self.videoUrl输入视频的路径//封面图片NSDictionary *opts = [NSDictionary dictionaryWithObject:@(YES) forKey:AVURLAssetPreferPreciseDurationAndTimingKey];//    NSDictionary *opts = [NSDictionary dictionaryWithObjectsAndKeys:@(YES),AVURLAssetPreferPreciseDurationAndTimingKey,AVAssetReferenceRestrictionForbidNone,AVURLAssetReferenceRestrictionsKey, nil];videoAsset = [AVURLAsset URLAssetWithURL:videoPath options:opts];     //初始化视频媒体文件//开始时间CMTime startCropTime = CMTimeMakeWithSeconds(startTime, 600);//结束时间CMTime endCropTime = CMTimeMakeWithSeconds(endTime, 600);if (endTime == 0) {endCropTime = CMTimeMakeWithSeconds(videoAsset.duration.value/videoAsset.duration.timescale-startTime, videoAsset.duration.timescale);}//2 创建AVMutableComposition实例. apple developer 里边的解释 【AVMutableComposition is a mutable subclass of AVComposition you use when you want to create a new composition from existing assets. You can add and remove tracks, and you can add, remove, and scale time ranges.】AVMutableComposition *mixComposition = [AVMutableComposition composition];//有声音if ([[videoAsset tracksWithMediaType:AVMediaTypeAudio] count] > 0){//声音采集AVURLAsset * audioAsset = [[AVURLAsset alloc] initWithURL:videoPath options:opts];//音频通道AVMutableCompositionTrack * audioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];//音频采集通道AVAssetTrack * audioAssetTrack = [[audioAsset tracksWithMediaType:AVMediaTypeAudio] lastObject];[audioTrack insertTimeRange:CMTimeRangeMake(startCropTime, endCropTime) ofTrack:audioAssetTrack atTime:kCMTimeZero error:nil];}//3 视频通道  工程文件中的轨道，有音频轨、视频轨等，里面可以插入各种对应的素材AVMutableCompositionTrack *videoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideopreferredTrackID:kCMPersistentTrackID_Invalid];NSError *error;//把视频轨道数据加入到可变轨道中 这部分可以做视频裁剪TimeRange[videoTrack insertTimeRange:CMTimeRangeMake(startCropTime, endCropTime)ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] lastObject]atTime:kCMTimeZero error:&error];//3.1 AVMutableVideoCompositionInstruction 视频轨道中的一个视频，可以缩放、旋转等AVMutableVideoCompositionInstruction *mainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];mainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, videoTrack.timeRange.duration);// 3.2 AVMutableVideoCompositionLayerInstruction 一个视频轨道，包含了这个轨道上的所有视频素材AVMutableVideoCompositionLayerInstruction *videolayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];AVAssetTrack *videoAssetTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] lastObject];UIImageOrientation videoAssetOrientation_  = UIImageOrientationUp;//拍摄的时候视频是否是竖屏拍的BOOL isVideoAssetvertical  = NO;CGAffineTransform videoTransform = videoAssetTrack.preferredTransform;if (videoTransform.a == 0 && videoTransform.b == 1.0 && videoTransform.c == -1.0 && videoTransform.d == 0) {isVideoAssetvertical = YES;videoAssetOrientation_ =  UIImageOrientationUp;//正着拍}if (videoTransform.a == 0 && videoTransform.b == -1.0 && videoTransform.c == 1.0 && videoTransform.d == 0) {//        videoAssetOrientation_ =  UIImageOrientationLeft;isVideoAssetvertical = YES;videoAssetOrientation_ = UIImageOrientationDown;//倒着拍}if (videoTransform.a == 1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == 1.0) {isVideoAssetvertical = NO;videoAssetOrientation_ =  UIImageOrientationLeft;//左边拍的}if (videoTransform.a == -1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == -1.0) {isVideoAssetvertical = NO;videoAssetOrientation_ = UIImageOrientationRight;//右边拍}float scaleX = 1.0,scaleY = 1.0,scale = 1.0;CGSize originVideoSize;if (isVideoAssetvertical || Assetvertical) {originVideoSize = CGSizeMake([[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].height, [[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].width);}else{originVideoSize = CGSizeMake([[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].width, [[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].height);}float x = videoDealPoint.x;float y = videoDealPoint.y;if (shouldScale) {scaleX = videoSize.width/originVideoSize.width;scaleY = videoSize.height/originVideoSize.height;scale  = MAX(scaleX, scaleY);if (scaleX>scaleY) {NSLog(@"竖屏");}else{NSLog(@"横屏");}}else{scaleX = 1.0;scaleY = 1.0;scale = 1.0;}if (Assetvertical) {CGAffineTransform trans = CGAffineTransformMake(videoAssetTrack.preferredTransform.a*scale, videoAssetTrack.preferredTransform.b*scale, videoAssetTrack.preferredTransform.c*scale, videoAssetTrack.preferredTransform.d*scale, videoAssetTrack.preferredTransform.tx*scale-x+720, videoAssetTrack.preferredTransform.ty*scale-y);//    [videolayerInstruction setTransform:trans atTime:kCMTimeZero];CGAffineTransform trans2 = CGAffineTransformRotate(trans, M_PI_2);[videolayerInstruction setTransform:trans2 atTime:kCMTimeZero];}else{CGAffineTransform trans = CGAffineTransformMake(videoAssetTrack.preferredTransform.a*scale, videoAssetTrack.preferredTransform.b*scale, videoAssetTrack.preferredTransform.c*scale, videoAssetTrack.preferredTransform.d*scale, videoAssetTrack.preferredTransform.tx*scale-x, videoAssetTrack.preferredTransform.ty*scale-y);[videolayerInstruction setTransform:trans atTime:kCMTimeZero];}//裁剪区域//    [videolayerInstruction setCropRectangle:CGRectMake(0, 0, 720, 720) atTime:kCMTimeZero];// 3.3 - Add instructionsmainInstruction.layerInstructions = [NSArray arrayWithObjects:videolayerInstruction,nil];//AVMutableVideoComposition：管理所有视频轨道，可以决定最终视频的尺寸，裁剪需要在这里进行AVMutableVideoComposition *mainCompositionInst = [AVMutableVideoComposition videoComposition];CGSize naturalSize;//    if(isVideoAssetvertical){//        naturalSize = CGSizeMake(videoAssetTrack.naturalSize.height, videoAssetTrack.naturalSize.width);//    } else {//        naturalSize = videoAssetTrack.naturalSize;//    }naturalSize = originVideoSize;int64_t renderWidth = 0, renderHeight = 0;if (videoSize.height ==0.0 || videoSize.width == 0.0) {renderWidth = naturalSize.width;renderHeight = naturalSize.height;}else{renderWidth = ceil(videoSize.width);renderHeight = ceil(videoSize.height);}mainCompositionInst.renderSize = CGSizeMake(renderWidth, renderHeight);mainCompositionInst.instructions = [NSArray arrayWithObject:mainInstruction];mainCompositionInst.frameDuration = CMTimeMake(1, 30);// 4 - 输出路径NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);NSString *documentsDirectory = [paths objectAtIndex:0];NSString *myPathDocs =  [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.mp4",fileName]];unlink([myPathDocs UTF8String]);NSURL* videoUrl = [NSURL fileURLWithPath:myPathDocs];//    dlink = [CADisplayLink displayLinkWithTarget:self selector:@selector(updateProgress)];//    [dlink setFrameInterval:15];//    [dlink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];//    [dlink setPaused:NO];// 5 - 视频文件输出exporter = [[AVAssetExportSession alloc] initWithAsset:mixCompositionpresetName:AVAssetExportPresetHighestQuality];exporter.outputURL=videoUrl;exporter.outputFileType = AVFileTypeMPEG4;exporter.shouldOptimizeForNetworkUse = YES;exporter.videoComposition = mainCompositionInst;[exporter exportAsynchronouslyWithCompletionHandler:^{dispatch_async(dispatch_get_main_queue(), ^{//这里是输出视频之后的操作，做你想做的[self cropExportDidFinish:exporter];});}];
}- (void)cropExportDidFinish:(AVAssetExportSession*)session {if (session.status == AVAssetExportSessionStatusCompleted) {NSURL *outputURL = session.outputURL;dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{[SVProgressHUD dismiss];__block PHObjectPlaceholder *placeholder;if (UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(outputURL.path)) {NSError *error;[[PHPhotoLibrary sharedPhotoLibrary] performChangesAndWait:^{PHAssetChangeRequest* createAssetRequest = [PHAssetChangeRequest creationRequestForAssetFromVideoAtFileURL:outputURL];placeholder = [createAssetRequest placeholderForCreatedAsset];} error:&error];if (error) {[SVProgressHUD showErrorWithStatus:[NSString stringWithFormat:@"%@",error]];}else{[SVProgressHUD showSuccessWithStatus:@"视频已经保存到相册"];}}else {[SVProgressHUD showErrorWithStatus:NSLocalizedString(@"视频保存相册失败，请设置软件读取相册权限", nil)];}});}else{NSLog(@"%@",session.error);[SVProgressHUD showErrorWithStatus:NSLocalizedString(@"裁剪失败", nil)];}
}// 将JSONDATA转化为字典或者数组
- (id)DataToArrayOrNSDictionary:(NSData *)jsonData{NSError *error = nil;id jsonObject = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingAllowFragments error:&error];if (jsonObject != nil && error == nil){return jsonObject;}else{// 解析错误return nil;}
}// 将JSON串转化为字典或者数组
- (id)StrToArrayOrNSDictionary:(NSString *)jsonStr {NSData *jsonData = [jsonStr dataUsingEncoding:NSUTF8StringEncoding];return [self DataToArrayOrNSDictionary:jsonData];
}

调用的时候，直接使用

-(void)cropImage{NSURL *videoPath = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"selfS" ofType:@"MOV"]];[self saveVideoPath:videoPath withStartTime:0.1 withEndTime:0 withSize:CGSizeMake(300, 300) withVideoDealPoint:CGPointMake(50, 50) WithFileName:@"cropVideo" shouldScale:YES];
}

其实对于一般的视频裁剪，只需要使用下面这个函数即可

- (void)goSaveVideoPath:(NSURL*)videoPath withStartTime:(float)startTime withEndTime:(float)endTime withSize:(CGSize)videoSize withVideoDealPoint:(CGPoint)videoDealPoint WithFileName:(NSString*)fileName shouldScale:(BOOL)shouldScale isWxVideoAssetvertical:(BOOL)Assetvertical

1.1、微信的处理

但是在实际使用过程中发现，单独使用这个函数中的AVFoundation处理裁剪视频的时候，对微信的支持并不好，如果使用微信自带的相机拍摄那个十秒视频虽然可以裁剪成功，但是是蓝屏的，只有声音没有画面，在打印的metadata信息中对比发现

WX拍摄2017-05-11 19:35:58.529751+0800 JianLiXiu[9592:2774766] ======metadata:uiso/dscp,{dataType = 2;dataTypeNamespace = "com.apple.quicktime.udta";
},{"WXVer":369428256},com.apple.metadata.datatype.UTF-8
2017-05-11 19:35:58.531034+0800 JianLiXiu[9592:2774766] ======commonMetadata:uiso/dscp,{dataType = 2;dataTypeNamespace = "com.apple.quicktime.udta";
},{"WXVer":369428256},com.apple.metadata.datatype.UTF-8WX下载======metadata:uiso/dscp,{dataType = 2;dataTypeNamespace = "com.apple.quicktime.udta";
},{"WXVer":369428256},com.apple.metadata.datatype.UTF-8======commonMetadata:uiso/dscp,{dataType = 2;dataTypeNamespace = "com.apple.quicktime.udta";
},{"WXVer":369428256},com.apple.metadata.datatype.UTF-8自带拍摄2017-05-11 19:35:09.708010+0800 JianLiXiu[9592:2774253] ======metadata:uiso/loci,{dataType = 2;dataTypeNamespace = "com.apple.quicktime.udta";
},+31.1711+121.3836+045.636/,com.apple.metadata.datatype.UTF-8
2017-05-11 19:35:09.710245+0800 JianLiXiu[9592:2774253] ======metadata:uiso/date,{dataType = 0;dataTypeNamespace = "com.apple.quicktime.udta";
},2017-05-11T17:40:41+0800,com.apple.metadata.datatype.raw-data
2017-05-11 19:35:09.712193+0800 JianLiXiu[9592:2774253] ======commonMetadata:uiso/date,{dataType = 0;dataTypeNamespace = "com.apple.quicktime.udta";
},2017-05-11T17:40:41+0800,com.apple.metadata.datatype.raw-data
2017-05-11 19:35:09.712746+0800 JianLiXiu[9592:2774253] ======commonMetadata:uiso/loci,{dataType = 2;dataTypeNamespace = "com.apple.quicktime.udta";
},+31.1711+121.3836+045.636/,com.apple.metadata.datatype.UTF-8

所以通过视频的metadata信息来判断是不是微信的视频，通过metadata是否含有{"WXVer":369428256}这个来判断是不是微信处理过的视频，如果是微信的视频先使用GPUImage重新渲染编码一次然后再处理。

代码中的

CGAffineTransform videoTransform = videoAssetTrack.preferredTransform;

是代表的视频的拍摄方向，在正常拍摄的时候打印如下

自带竖 0,1,-1,0
自带横 1,0,0,1qq竖 1,0,0,1
qq横 0,-1,1,0微信竖 0,1,-1,0
微信横 1,0,0,1

但微信的视频在GPUImage重新录制之后，拍摄方向变成了

微信竖 1,0,0,1
微信横 1,0,0,1

也就是说不管横竖，全部变成了一样的，这样就导致横屏拍摄的时候裁剪正常，竖屏拍摄的时候，裁剪之后出来的视频时错误的，所以要先判断原视频是什么方向，之后在裁剪处理的时候去处理。

1.2、裁剪位置的选择

int64_t renderWidth = 0, renderHeight = 0;

是要渲染输出的视频大小是多少，所以如果想设置指定大小，那就在这个设置，输出的大小就可以了，但是这个裁剪是默认从(0,0)开始的，如果是从中间开始的就需要设置videolayerInstruction 这个的移动了。

videolayerInstruction是这个视频轨的动画等移动效果，视频的移动，翻转，缩小等都在这个上面进行操作。通过设置CGAffineTransform来达到裁剪位置

x会跟着c的值进行拉伸(View的宽度是跟着改变)，y会跟着b的值进行拉伸（View的高度跟着改变），要注意到的是c和b的值改变不会影响到View的point（center中心点）的改变。这是个很有意思的两个参数。

x会跟着t.x进行x做表平移，y会跟着t.y进行平移。这里的point（center）是跟着变换的。

下面是Apple整合的transform

平移：

①根据本身的transform进行平移 CGAffineTransformMakeTranslation(CGFloat tx,CGFloat ty)

②根据本身的transform后者另外的transform进行平移CGAffineTransformTranslate(CGAffineTransform t,CGFloat tx,CGFloat ty)

缩放：

①根据本身的transform进行缩放

CGAffineTransformMakeScale(CGFloat sx,CGFloat sy)

②根据本身的transform后者另外的transform进行缩放

CGAffineTransformScale(CGAffineTransform t,CGFloat sx,CGFloat sy)

旋转：

① 根据本身的transform进行旋转

CGAffineTransformMakeRotation(CGFloat angle) （angle 旋转的角度）

②根据本身的transform后者另外的transform进行旋转

CGAffineTransformRotate(CGAffineTransform t,CGFloat angle)

具体可以参考《iOS 仿射变换CGAffineTransform详解》

所以结合渲染的大小和要移动的效果，就可以知道是从哪个点开始裁剪，裁剪多大的视频了。

1.3、裁剪时间的选择

裁剪时间主要是在视频轨和音轨编辑的时候，设置插入的时长，从而控制裁剪时间。

//把视频轨道数据加入到可变轨道中 这部分可以做视频裁剪TimeRange[videoTrack insertTimeRange:CMTimeRangeMake(startCropTime, endCropTime)ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] lastObject]atTime:kCMTimeZero error:&error];

1.4、对没有声音视频的处理，比如延时视频

上篇说了如果没有声音的视频在处理的时候会错误，所以在裁剪的时候也要注意是否含有声音，如果没有声音就不要添加音轨了

 //有声音if ([[videoAsset tracksWithMediaType:AVMediaTypeAudio] count] > 0){//声音采集AVURLAsset * audioAsset = [[AVURLAsset alloc] initWithURL:videoPath options:opts];//音频通道AVMutableCompositionTrack * audioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];//音频采集通道AVAssetTrack * audioAssetTrack = [[audioAsset tracksWithMediaType:AVMediaTypeAudio] lastObject];[audioTrack insertTimeRange:CMTimeRangeMake(startCropTime, endCropTime) ofTrack:audioAssetTrack atTime:kCMTimeZero error:nil];}

1.5、原视频大小的处理

如果不裁剪视频的大小，只是默认大小裁剪时间的时候，发现获取的naturalSize在竖屏的时候是错误的，比如一个视频720*1280，结果获得的naturalSize是1280*720，横竖刚好相反，所以需要对竖屏的大小进行处理一下，这样就是正确的了

 if (isVideoAssetvertical || Assetvertical) {originVideoSize = CGSizeMake([[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].height, [[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].width);}else{originVideoSize = CGSizeMake([[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].width, [[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].height);}

二、视频拼接、音视频的处理

视频的拼接和音视频的拼接是一样的，都是处理视频轨和音轨的开始时间，如果第二个视频的开始时间是第一个视频的结束时间，那么就是两段视频的拼接，如果开始时间相同，那么就是两个视频在混合了。

下面给出一个两个视频拼接，再加上一个背景音乐的例子。

-(void)addFirstVideo:(NSURL*)firstVideoPath andSecondVideo:(NSURL*)secondVideo withMusic:(NSURL*)musicPath{[SVProgressHUD showWithStatus:@"正在合成到系统相册中"];AVAsset *firstAsset = [AVAsset assetWithURL:firstVideoPath];AVAsset *secondAsset = [AVAsset assetWithURL:secondVideo];AVAsset *musciAsset = [AVAsset assetWithURL:musicPath];// 1 - Create AVMutableComposition object. This object will hold your AVMutableCompositionTrack instances.AVMutableComposition *mixComposition = [[AVMutableComposition alloc] init];// 2 - Video trackAVMutableCompositionTrack *firstTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideopreferredTrackID:kCMPersistentTrackID_Invalid];[firstTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, firstAsset.duration)ofTrack:[[firstAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:kCMTimeZero error:nil];[firstTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, secondAsset.duration)ofTrack:[[secondAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:firstAsset.duration error:nil];if (musciAsset!=nil){AVMutableCompositionTrack *AudioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudiopreferredTrackID:kCMPersistentTrackID_Invalid];[AudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, CMTimeAdd(firstAsset.duration, secondAsset.duration))ofTrack:[[musciAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:kCMTimeZero error:nil];}// 4 - Get pathNSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);NSString *documentsDirectory = [paths objectAtIndex:0];NSString *myPathDocs =  [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"mergeVideo-%d.mov",arc4random() % 1000]];NSURL *url = [NSURL fileURLWithPath:myPathDocs];// 5 - Create exporterexporter = [[AVAssetExportSession alloc] initWithAsset:mixCompositionpresetName:AVAssetExportPresetHighestQuality];exporter.outputURL=url;exporter.outputFileType = AVFileTypeQuickTimeMovie;exporter.shouldOptimizeForNetworkUse = YES;[exporter exportAsynchronouslyWithCompletionHandler:^{dispatch_async(dispatch_get_main_queue(), ^{[self exportDidFinish:exporter];});}];
}- (void)exportDidFinish:(AVAssetExportSession*)session {if (session.status == AVAssetExportSessionStatusCompleted) {NSURL *outputURL = session.outputURL;dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{[SVProgressHUD dismiss];__block PHObjectPlaceholder *placeholder;if (UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(outputURL.path)) {NSError *error;[[PHPhotoLibrary sharedPhotoLibrary] performChangesAndWait:^{PHAssetChangeRequest* createAssetRequest = [PHAssetChangeRequest creationRequestForAssetFromVideoAtFileURL:outputURL];placeholder = [createAssetRequest placeholderForCreatedAsset];} error:&error];if (error) {[SVProgressHUD showErrorWithStatus:[NSString stringWithFormat:@"%@",error]];}else{[SVProgressHUD showSuccessWithStatus:@"视频已经保存到相册"];}}else {[SVProgressHUD showErrorWithStatus:NSLocalizedString(@"视频保存相册失败，请设置软件读取相册权限", nil)];}});}
}

调用的时候

-(void)addMusic{NSURL *videoPath1 = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"selfS" ofType:@"MOV"]];NSURL *videoPath2 = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"selfH" ofType:@"MOV"]];NSURL *music = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"music" ofType:@"mp3"]];[self addFirstVideo:videoPath1 andSecondVideo:videoPath2 withMusic:music];
}

这样就是videopath1和videopath2拼接，然后加上一个背景音乐music，之后生成一个视频保存到相册。

(2017-08-14)2.1、音频音量的调节

最近需要把背景音乐的音量调小，当然背景音乐文件音量调小即可，但是毕竟每个文件处理都不太方便，所以还是用代码把指定音轨的音量减小，这里只减小背景音乐的音量，不减小其他的音量，所以用到了AVMutableAudioMix这个。

在原工程增加以下代码即可

//修改背景音乐的音量startAVMutableAudioMix *videoAudioMixTools = [AVMutableAudioMix audioMix];if (musciAsset) {//调节音量//获取音频轨道AVMutableAudioMixInputParameters *firstAudioParam = [AVMutableAudioMixInputParameters audioMixInputParametersWithTrack:AudioTrack];//设置音轨音量,可以设置渐变,设置为1.0就是全音量[firstAudioParam setVolumeRampFromStartVolume:1.0 toEndVolume:1.0 timeRange:CMTimeRangeMake(kCMTimeZero, CMTimeAdd(firstAsset.duration, secondAsset.duration))];[firstAudioParam setTrackID:AudioTrack.trackID];videoAudioMixTools.inputParameters = [NSArray arrayWithObject:firstAudioParam];}//end
exporter.audioMix = videoAudioMixTools;

三、demo下载

github下载：https://github.com/DamonHu/VideoEditDemo

gitosc下载：http://git.oschina.net/DamonHoo/VideoEditDemo

四、demo演示

五、总结

本篇已完结，在视频的处理上面主要就是对视频轨、音频轨的活用，当然以后还有字幕轨等，但是原理都是一样的，参看里面的源码即可看到所有轨道的编辑。GPUImage是一个很好的补充，在渲染方面很好用，可以结合一下采用最适合项目的方案。

在项目中碰到了很多问题，在demo中尽量避免了这类问题，如果你也碰到了，可以看看谷歌，我下面的参考文章也是碰到问题时看到的有价值的文章，希望对你有用。

六、参考文章

讲解篇

iOS 视频旋转及平移详解
iOS 仿射变换CGAffineTransform详解
iOS视频功能模块的开发
iOS之AVFoundation视频转码
AVFoundation之AVAsset
iOS视频录制、压缩导出、取帧
IOS视频添加背景音乐同时保留原音
iOS图片渲染
《视频直播技术详解》系列之一：视频采集和处理
【如何快速的开发一个完整的iOS直播app】(原理篇)
iOS视频编辑学习笔记（1）-AVAsset、AVMutableComposition系列类的理解及视频裁
iOS 音视频高级编程：AVAsset、CoreVideo、VideoToolbox、FFmpeg与CMTime
iOS获取本地视频和网络URL视频的缩略图方法
Video Manipulation in iOS : Resizing,Merging and Overlapping Videos in iOS
AVFoundation和 GPUImage初探
iOS-----AVFoundation框架的功能详解
AVComposition中的CALayer
AVFoundation(二)：核心AVAsset
iOS AVFoundation 视频暂停多视频合成流程
分段录制的实现
一、音视频配置文档概念

BUG篇

naturalSize returning wrong orientation from AVURLAsset
AVMutableVideoComposition rotated video captured in portrait modeAsk
Error Domain=AVFoundationErrorDomain Code=-11800 "这项操作无法完成"
ios视频、图片翻转问题
AVPlayer Video Gravity Positioning?
Fix GPUImageMovieWriter isPaused
Crash when app goes in background.
Added pause/resume methods to the GPUImageMovieWriter
[GPUImageMovieWriter 无法2次录像报错：[AVAssetWriter startWriting] Cannot call method when status is 3](http://www.jianshu.com/p/bd204b34a85d)
Issue when saving videos
AVAssetWriter fails when calling finishWritingWithCompletionHandler
SimpleVideoFileFilter sample crash in GPUImageMovieWriter's finishRecordingWithCompletionHandler
GPUImageMovieWriter - crashing with “Cannot call method when status is 2”
AVAssetWriter finishWritingWithCompletionHandler函数没有正常执行的原因
https://github.com/BradLarson/GPUImage/issues/1203
GPUImageMovieWriter原生BUG(1)时间戳问题

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