Most people download videos from YouTube using DownThemAll or some other similar download manager. This downloads the video in Flash video (FLV) format – which means that you generally need to convert it to some other format to make it playable on handheld devices, editable by movies editors, et al. The conversion process itself can result in a lower quality file being output after transcoding. The other option is get the transcoding done using some online service like Zamzar and downloading the transcoded file. (This is the option which I use.)
You’ve a third option now – downloading an MP4 version of any video directly from YouTube. MPEG-4 is a format which, albeit proprietary, enjoys more supports than FLV – especially in portable media player devices. This option was available earlier for some Google Video videos but it was strictly an opt-in feature. The method I’m going to mention would work for every video. All you need to do is to drag the two bookmarklets into your bookmarks menu / bar:
YouTube standard quality video download
YouTube high quality video download
The first link allows you to download a standard quality video, which would be available for every video. Click on this bookmarklet when you’re on a YouTube video page (NOT a results page) and you’ll get a file download box prompting you to save a ‘.mp4’ file. The second link allows you to download a higher quality version of the video you’re watching, but this is restricted to only those few videos which were uploaded in high quality in the first place. (If you click on the bookmarklet and nothing happens, you know that the high quality version of that video is not available.)