Ciao EF,
Like Alan_B (our local enfant terrible) says they compress really low and the quality will remain the same. If I understood well you want to download and keep the files. Here’s a crack I used and works to download the .flv and then convert to mp4 and even improve quality somewhat. Here are the step by step instructions for Mac (for some reason I think you use Mac…).
I’ll paste below the link to the site in case you need to work on PC.
A) First steps is getting the video onto your desktop (works for (PC, Mac, Linux) :
Any web browser
Go to YouTube.com and find a clip you like. Every video page on YouTube has a little EMBED box that allows you copy code and post YouTube video clips on your website. We are going to take advanage of this.
(the embed box is to the right of the clip below the URL box. You must use this or it will not work)
* Copy the code and paste it into a text edit program like TextEdit (Mac) or Notepad (PC). The code will look something like this:
<object width=“425” height=“350”>
</param> </param><embed src=“http://www.youtube.com/v/-oNQXLNMh0c” type=“application/x-shockwave-flash” wmode=“transparent” width=“425” height=“350”></embed></object>
* You are looking for the URL of the video file. In the example above that would be: http://www.youtube.com/v/-oNQXLNMh0c. Copy this URL and paste it into a new web browser window and press the Return/Enter key on your keyboard.
* The YouTube clip should load your web browser as a full screen clip. Press play and wait for the video to load.
* Now take a closer look at the URL. It’s different than what you pasted in there. It’s a lot longer right? It should look something like this: http://www.youtube.com/p.swf?video_id= -oNQXLNMh0c&eurl;=&iurl=http://sjl-static5.sjl.youtube.com/vi/-oNQXLNMh0c/2.jpg&t=OEgsToPDskJaNd08X90swYCiZMZTzBdb
* The next step is to change the piece of code that says “p.swf” to “get_video”. So the example above should look like this after the change: &t=OEgsToPDskJaNd08X90swYCiZMZTzBdb
* Press return and your video will start to download.
* Save it to your Desktop
B) Convert to MP4 for Mac using Isquint. Drag and drop stuff, easy.
http://www.isquint.org/
Voilà.
BB
source : http://www.methodshop.com/mp3/tutorials/youtuberip/