iOS 视频压缩

- (void)convertVideoToLowQuailtyWithInputURL:(NSURL*)inputURL

                                   outputURL:(NSURL*)outputURL

                                     handler:(void (^)(AVAssetExportSession*))handler {

    [[NSFileManager defaultManager] removeItemAtURL:outputURL error:nil];

    AVURLAsset *urlAsset = [AVURLAsset URLAssetWithURL:inputURL options:nil];

    AVAssetExportSession *session = [[[AVAssetExportSession alloc] initWithAsset: urlAsset presetName:AVAssetExportPresetMediumQuality] autorelease];

    session.outputURL = outputURL;

    session.outputFileType = AVFileTypeQuickTimeMovie;

    [session exportAsynchronouslyWithCompletionHandler:^(void) {

        handler(session);

    }];

}