IOS 中视频和音乐合成

/**
为了方便，我都将选取的视频和音乐文件以及导出的视频将路径设置在桌面上了,资源文件自己设置
**/

NSString *inputFilePath = @"/Users/vs/Desktop/testvideo.mp4"; // 来源路径
NSString *outputFilePath = @"/Users/vs/Desktop/exportMax.mp4"; // 输出路径
NSString *mp3Path = @"/Users/vs/Desktop/月半弯.mp3";
//时间起点
CMTime nextClistartTime = kCMTimeZero;
//创建可变的音视频组合
AVMutableComposition * comosition = [AVMutableComposition composition];

//视频采集
AVURLAsset * videoAsset = [[AVURLAsset alloc] initWithURL:[NSURL fileURLWithPath:inputFilePath] options:nil];
//视频时间范围
CMTimeRange videoTimeRange = CMTimeRangeMake(kCMTimeZero, videoAsset.duration);
// 视频通道 枚举 kCMPersistentTrackID_Invalid = 0
AVMutableCompositionTrack * videoTrack = [comosition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
//视频采集通道
AVAssetTrack * videoAssetTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] firstObject];
//把采集轨道数据加入到可变轨道中
[videoTrack insertTimeRange:videoTimeRange ofTrack:videoAssetTrack atTime:nextClistartTime error:nil];

//声音采集
AVURLAsset * audioAsset = [[AVURLAsset alloc] initWithURL:[NSURL fileURLWithPath:mp3Path] options:nil];
//因为视频较短 所以直接用了视频的长度 如果想要自动化需要自己写判断
CMTimeRange audioTimeRange = videoTimeRange;
//音频通道
AVMutableCompositionTrack * audioTrack = [comosition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
//音频采集通道
AVAssetTrack * audioAssetTrack = [[audioAsset tracksWithMediaType:AVMediaTypeAudio] firstObject];
//加入合成轨道中
[audioTrack insertTimeRange:audioTimeRange ofTrack:audioAssetTrack atTime:nextClistartTime error:nil];

#warning test
// 3.1 - Create AVMutableVideoCompositionInstruction
AVMutableVideoCompositionInstruction *mainInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
mainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, videoAsset.duration);

// 3.2 - Create an AVMutableVideoCompositionLayerInstruction for the video track and fix the orientation.
AVMutableVideoCompositionLayerInstruction *videolayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];
UIImageOrientation videoAssetOrientation_  = UIImageOrientationUp;
BOOL isVideoAssetPortrait_  = NO;
CGAffineTransform videoTransform = videoAssetTrack.preferredTransform;
if (videoTransform.a == 0 && videoTransform.b == 1.0 && videoTransform.c == -1.0 && videoTransform.d == 0) {
videoAssetOrientation_ = UIImageOrientationRight;
isVideoAssetPortrait_ = YES;
}
if (videoTransform.a == 0 && videoTransform.b == -1.0 && videoTransform.c == 1.0 && videoTransform.d == 0) {
videoAssetOrientation_ =  UIImageOrientationLeft;
isVideoAssetPortrait_ = YES;
}
if (videoTransform.a == 1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == 1.0) {
videoAssetOrientation_ =  UIImageOrientationUp;
}
if (videoTransform.a == -1.0 && videoTransform.b == 0 && videoTransform.c == 0 && videoTransform.d == -1.0) {
videoAssetOrientation_ = UIImageOrientationDown;
}
[videolayerInstruction setTransform:videoAssetTrack.preferredTransform atTime:kCMTimeZero];
[videolayerInstruction setOpacity:0.0 atTime:videoAsset.duration];

// 3.3 - Add instructions
mainInstruction.layerInstructions = [NSArray arrayWithObjects:videolayerInstruction,nil];

AVMutableVideoComposition *mainCompositionInst = [AVMutableVideoComposition videoComposition];

CGSize naturalSize;
if(isVideoAssetPortrait_){
naturalSize = CGSizeMake(videoAssetTrack.naturalSize.height, videoAssetTrack.naturalSize.width);
} else {
naturalSize = videoAssetTrack.naturalSize;
}
float renderWidth, renderHeight;
renderWidth = naturalSize.width;
renderHeight = naturalSize.height;
mainCompositionInst.renderSize = CGSizeMake(renderWidth, renderHeight);
mainCompositionInst.instructions = [NSArray arrayWithObject:mainInstruction];
mainCompositionInst.frameDuration = CMTimeMake(1, 30);
#warning TODO: test end 如果没有这段代码，合成后的视频会旋转90度

//创建输出
AVAssetExportSession * assetExport = [[AVAssetExportSession alloc] initWithAsset:comosition presetName:AVAssetExportPresetMediumQuality];
assetExport.outputURL = [NSURL fileURLWithPath:outputFilePath];//输出路径
assetExport.outputFileType = AVFileTypeMPEG4;//输出类型
assetExport.shouldOptimizeForNetworkUse = YES;
assetExport.videoComposition = mainCompositionInst;
[assetExport exportAsynchronouslyWithCompletionHandler:^{
dispatch_async(dispatch_get_main_queue(), ^{
//            [self exportDidFinish:assetExport];
switch (assetExport.status) {
case AVAssetExportSessionStatusFailed: // 失败
NSLog(@"exportSessionError: %@",assetExport.error.description);
break;
case AVAssetExportSessionStatusExporting:
NSLog(@"AVAssetExportSessionExporting");
break;
case AVAssetExportSessionStatusCompleted: // 成功
NSLog(@"exportSessionCompleted");

UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示" message:@"保存成功！"
delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
[alert show];

break;
}

});
}];