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];
        }];
    }
}