Doesn't look to me like the mod's the problem. When I convert my own videos and select lower quality setting than I should, that's what I end up with too ... a video that looks kind a crappy yet sounds pretty decent. Problem with videos is that you can't really upload huge videos like that productively (in most cases) and consequently the quality is made to (intentionally) suffer during the conversion process, to turn a gigantic video into merely a large video for efficiency purposes. My suggestion see more ... get a copy of the full original video and either reconvert it with higher quality settings, or use it as is, meaning the original unconverted file.

Greetings from Germany