IOS视频压缩功能实现

         NSString *path=@ “视频原路径”
         NSString *bakPath=@ “视频新路径”//新路径不能存在文件 如果存在是不能压缩成功的
        AVURLAsset *avAsset = [AVURLAsset URLAssetWithURL:[NSURL fileURLWithPath:path] options:nil];
        AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:avAsset presetName:AVAssetExportPreset1280x720];
        exportSession.outputURL = [NSURL fileURLWithPath:bakPath];
        exportSession.outputFileType = AVFileTypeMPEG4;
        exportSession.shouldOptimizeForNetworkUse= YES;
        [exportSession exportAsynchronouslyWithCompletionHandler:^(void)
         {
             BOOL goToUploadFile=NO;
             switch (exportSession.status) {
                 case AVAssetExportSessionStatusCancelled:
                     NSLog(@"AVAssetExportSessionStatusCancelled");
                     break;
                 case AVAssetExportSessionStatusUnknown:
                     NSLog(@"AVAssetExportSessionStatusUnknown");
                     break;
                 case AVAssetExportSessionStatusWaiting:
                     NSLog(@"AVAssetExportSessionStatusWaiting");
                     break;
                 case AVAssetExportSessionStatusExporting:
                     NSLog(@"AVAssetExportSessionStatusExporting");
                     break;
                 case AVAssetExportSessionStatusCompleted:
                   
                    _path=bakPath;
                  //压缩成功
               
                     break;
                 case AVAssetExportSessionStatusFailed:
                 {
                     NSError *error=exportSession.error;
                     if (error) {
                      
                     }
                 }
                     
                    break;
                  default:
                    
                     break;
             }
            
         }];