MOV_TO_MP4

-(void)MovToMp4{    AVURLAsset *avAsset = [AVURLAsset URLAssetWithURL:[NSURL fileURLWithPath:screenFilePath] options:nil];        NSArray *compatiblePresets = [AVAssetExportSession exportPresetsCompatibleWithAsset:avAsset];        if ([compatiblePresets containsObject:AVAssetExportPresetLowQuality])            {                AVAssetExportSession *exportSession = [[AVAssetExportSession alloc]initWithAsset:avAsset presetName:AVAssetExportPresetHighestQuality];                NSDateFormatter* formater = [[NSDateFormatter alloc] init];        [formater setDateFormat:@"yyyyMMddHHmmss"];        NSString *_mp4Path = [[NSHomeDirectory() stringByAppendingFormat:@"/Documents/%@.mp4", [formater stringFromDate:[NSDate date]]] retain];        [formater release];        exportSession.outputURL = [NSURL fileURLWithPath:_mp4Path];                exportSession.outputFileType = AVFileTypeMPEG4;                CMTime start = CMTimeMakeWithSeconds(1.0, 600);                CMTime duration = CMTimeMakeWithSeconds(3.0, 600);                CMTimeRange range = CMTimeRangeMake(start, duration);                exportSession.timeRange = range;                [exportSession exportAsynchronouslyWithCompletionHandler:^{                        switch ([exportSession status]) {                                    case AVAssetExportSessionStatusFailed:                    NSLog(@"Export failed: %@", [[exportSession error] localizedDescription]);                                        break;                                    case AVAssetExportSessionStatusCancelled:                                        NSLog(@"Export canceled");                                        break;                case AVAssetExportSessionStatusCompleted:                {                    NSLog(@"开始上传屏幕快照");                  [g_api UpdateScreen:_mp4Path];                   }                    break;                default:                                        break;                                }                        [exportSession release];                    }];            }}