I ran across the following article on CNET:
http://www.webware.com/8301-1_109-9883507-2.htmlI am on a broadband connection and have not tried this yet. If anyone discovers that it makes an improvement, please post that information in this thread so that all of us can make sure we are getting the best possible quality on YouTube downloads. We all know that some of them are pretty poor quality, so any help can't hurt.
HOW-TO
Tweaking YouTube's resolution settings the easy wayBy Josh Lowensohn – February 29, 2008, 4:35 PM PST
Higher resolutions or not, YouTube still tweaks the quality of its videos for users depending on what kind of connection they've got. So how about a workaround to make sure you're getting the best of the best? Bayme of the VideoHelp.com forums seems to have found a way to tweak the URL of some videos to force YouTube to serve you the version with the highest resolution. The good news? It's easy as pie. The bad news? It's not going to work on all your videos, and it's not noticeably better
To give it a spin, just drop
&fmt=6 at the end of the URL of any video you're watching. If YouTube has a higher quality version available on its servers, it'll start playing right away. Otherwise, you'll simply be staring at a loading symbol. Greasemonkey users can also download a simple script that adjusts all YouTube URLs automatically.
There's a long discussion over on the VideoHelp boards about which file types are retaining the most quality after automatic conversion. YouTube appears to be experimenting with a few variants of Flash and H.264, the latter of which became a major part of YouTube with the introduction of the iPhone and AppleTV--both of which access videos from the service without using Adobe's Flash player.