短视频从无到有 (十)视频自定义时间剪辑

实现视频自定义时间这个需求还是很简单，AVFoundation提供的AVAssetExportSession这个类可以很方便的实现这个功能。效果图如下：

IMG_5333.PNG

左右两边的拖拽框添加手势事件，通过触摸点的变化算出要seek的时间，调用playerView的seekToTime:方法即可。下面显示视频画面的可以用UIScrollView做，即取得视频的缩略图，放在UIScrollView上就行。取视频缩略图的代码如下：

 AVURLAsset *asset =[[AVURLAsset alloc]initWithURL:[NSURL fileURLWithPath:_filePath] options:nil];
    
    videoTotalTime =asset.duration.value/asset.duration.timescale;
    NSLog(@"视频总时长：_____%f",videoTotalTime);
    
    //获取帧率
    CGFloat fps =[[[asset tracksWithMediaType:AVMediaTypeVideo] firstObject] nominalFrameRate];
    
    NSLog(@"视频帧率_____%f",fps);
    AVAssetImageGenerator *generator =[[AVAssetImageGenerator alloc]initWithAsset:asset];
    generator.appliesPreferredTrackTransform =YES;
//    generator.requestedTimeToleranceBefore =kCMTimeZero;
 //   generator.requestedTimeToleranceAfter =kCMTimeZero;
    for (int i =1; i<= videoTotalTime; i++) {
       
        CMTime time =CMTimeMakeWithSeconds(i, fps);
        
        NSLog(@"时间结构体");
        CMTimeShow(time);
        NSValue *value =[NSValue valueWithCMTime:time];
        [self.framesArray addObject:value];
        
    }
    
    //自定义imageView的宽
     if (self.framesArray.count <=5) {
        
        imgWidth =scrollView.frame.size.width/self.framesArray.count;
        
    }else{
    
        imgWidth =50;
    }
    
   
    NSLog(@"imgWidth:%f___%@",imgWidth,self.framesArray);
    
    [generator generateCGImagesAsynchronouslyForTimes:self.framesArray completionHandler:^(CMTime requestedTime, CGImageRef  _Nullable image, CMTime actualTime, AVAssetImageGeneratorResult result, NSError * _Nullable error) {
        
        if (result ==AVAssetImageGeneratorSucceeded) {
            
            UIImageView *imageView =[[UIImageView alloc]initWithFrame:CGRectMake(imgWidth*count,0,imgWidth,66)];
            imageView.image =[UIImage imageWithCGImage:image];
            //主线程刷新UI
            dispatch_async(dispatch_get_main_queue(), ^{
                
               
                [scrollView addSubview:imageView];
                scrollView.contentSize =CGSizeMake(imgWidth*count, 0.0);
                
                
            });
            
            count++;
            
        }else if (result ==AVAssetImageGeneratorFailed){
            
            NSLog(@"出错了：%@",error.localizedDescription);
            
        }else if (result ==AVAssetImageGeneratorCancelled){
            
             NSLog(@"出错了：%@",error.localizedDescription);
        }
        
        
    }];

UI层面的东西就不再多说，大家自己实现即可。核心还是使用AVAssetExportSession导出视频时设定自定义的时间，代码如下：

//设定开始时间和结束时间
    CMTime start =CMTimeMakeWithSeconds(startTime, playerView.player.currentTime.timescale);
    CMTime duration =CMTimeMakeWithSeconds((endTime -startTime),playerView.player.currentTime.timescale);
    
    CMTimeRange timeRange =CMTimeRangeMake(start, duration);
 // 创建AVAsset对象
    AVAsset* asset = [AVAsset assetWithURL:[NSURL fileURLWithPath:videoPath]];
    // 创建AVAssetExportSession对象
    AVAssetExportSession * exporter = [[AVAssetExportSession alloc] initWithAsset:asset presetName:presetName];
    //优化网络
    exporter.shouldOptimizeForNetworkUse = YES;
    //设置输出路径
    exporter.outputURL =compressionFileURL;
    //设置输出类型
    exporter.outputFileType = outputFileType;
    exporter.timeRange =timeRange;
    [exporter exportAsynchronouslyWithCompletionHandler:^{
        
        dispatch_async(dispatch_get_main_queue(), ^{
            
            switch (exporter.status) {
                case AVAssetExportSessionStatusFailed:{
                    
                    if (completeBlock) {
                        
                        completeBlock(exporter.error,compressionFileURL);
                    }
                    
                    break;
                }
                case AVAssetExportSessionStatusCancelled:{
                    
                    NSLog(@"Export Status: Cancell");
                    
                    break;
                }
                case AVAssetExportSessionStatusCompleted: {
                    
                    if (completeBlock) {
                        
                        completeBlock(nil,compressionFileURL);
                    }
                    
                    
                    break;
                }
                case AVAssetExportSessionStatusUnknown: {
                    
                    NSLog(@"Export Status: Unknown");
                    break;
                }
                case AVAssetExportSessionStatusExporting : {
                    
                    NSLog(@"Export Status: Exporting");
                    break;
                }
                case AVAssetExportSessionStatusWaiting: {
                    
                    NSLog(@"Export Status: Wating");
                    break;
                }
                    
            };
            
        });
        
    }];

有什么问题，欢迎大家留言讨论。