使用系统录制器录制的视频分辨率大小不符合实际需求,而且内存比较大,所以对视频做了一个裁剪和压缩处理.

基本配置

//宽高比例
#define Ratio 0.7
AVURLAsset asset = [[AVURLAsset alloc]initWithURL:url options:nil];
NSTimeInterval duration = CMTimeGetSeconds(asset.duration);
NSLog(@”生成的视频片段:%@”,asset);
//拍摄时间总长
Float64 totalSecconds = duration;
//每秒录制帧数
int32_t framesPerSecond = 20;
AVMutableComposition composion = [[AVMutableComposition alloc]init];
CMPersistentTrackID ida = 0;

合并视频音频轨道

AVMutableCompositionTrack *firstTrack = [composion addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:ida];
AVMutableCompositionTrack *audioTrack = [composion addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:ida];
CMTime inserTime = kCMTimeZero;
[firstTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration) ofTrack:[asset tracksWithMediaType:AVMediaTypeVideo][0] atTime:inserTime error:nil];
[audioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration) ofTrack:[asset tracksWithMediaType:AVMediaTypeAudio][0] atTime:inserTime error:nil];
inserTime = CMTimeAdd(inserTime, asset.duration);

旋转视频图像 防止90度颠倒

firstTrack.preferredTransform = CGAffineTransformMakeRotation(M_PI_2);
NSLog(@”视频原尺寸:%@”,NSStringFromCGSize(firstTrack.naturalSize));

定义最终生成的尺寸

CGSize renderSize = CGSizeMake(firstTrack.naturalSize.height, firstTrack.naturalSize.height * Ratio);
NSLog(@”渲染后的尺寸:%@”,NSStringFromCGSize(renderSize));

通过AVMutableVideoComposition实现视频的裁剪(矩形，截取正中心区域视频)

AVMutableVideoComposition *videoComposition = [[AVMutableVideoComposition alloc]init];
videoComposition.frameDuration = CMTimeMake(1,framesPerSecond);
videoComposition.renderSize = renderSize;
AVMutableVideoCompositionInstruction instruction = [[AVMutableVideoCompositionInstruction alloc]init];
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(totalSecconds, framesPerSecond));
AVMutableVideoCompositionLayerInstruction transformer = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:firstTrack];
CGAffineTransform t1 = CGAffineTransformMakeTranslation(firstTrack.naturalSize.height, -(firstTrack.naturalSize.width-(firstTrack.naturalSize.height * Ratio))/2 );
CGAffineTransform t2 = CGAffineTransformRotate(t1, M_PI_2);
CGAffineTransform finalTransform = t2;
[transformer setTransform:finalTransform atTime:kCMTimeZero];
instruction.layerInstructions = @[transformer];
videoComposition.instructions = @[instruction];

处理后的视频路径

NSString *destinationPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).lastObject stringByAppendingPathComponent:@”myVidio2.mov”];
NSFileManager *manager = [NSFileManager defaultManager];
if ([manager fileExistsAtPath:destinationPath]){
[manager removeItemAtPath:destinationPath error:nil];
}
NSURL *videoPath = [NSURL fileURLWithPath:destinationPath];

对视频做相应的压缩

AVAssetExportSession *exporter = [[AVAssetExportSession alloc]initWithAsset:composion presetName:AVAssetExportPresetMediumQuality];//压缩等级
exporter.outputURL = videoPath;
exporter.outputFileType = AVFileTypeMPEG4;
exporter.videoComposition = videoComposition;
exporter.shouldOptimizeForNetworkUse = YES;
exporter.timeRange = CMTimeRangeMake(kCMTimeZero, CMTimeMakeWithSeconds(totalSecconds, framesPerSecond));
//处理成功后
[exporter exportAsynchronouslyWithCompletionHandler:^{
NSLog(@”压缩裁剪后的视频路径:%@”,destinationPath);
}];

githubDemo地址:

播放器 断点续传 视频压缩 视频录制工程中的VideoTailoring.h文件.