YouTube will take the average 15mbit dashcam video and re-encode it and compress it to anything from 2mbit to 4mbit, if you're not a high traffic page it's generally at the lower end though
I found it varies on file format , codec and compression ..
ATM I post video as AVI , MPEG4 and compression @ 10,000 Kbits / second ...
But you have to play around to see how it ends up on youtube ( After they have done their bit )
You could try MP4 - H264 , or maybe FLV ..
I know that FLV seems to give decent results .. But it all depends on the variables , and the software you are using ..
For me , If I do my compression bellow 10,000 Kbits / second , when youtube is done there is some visible loss ...
Above 10,000 ( 11,000 ) and its better ..
Change to a better format , codec and the results can improve ...
ATM I need to find a decent video converter so I can post FLV ...
VLC converts video , and for a long time it didn't work for me ( Video conversion ) , the software just crashed .
But recently I noticed that the video conversion function is working again .. ( So I will have to give VLC a little of my time to see what it can do )
Video quality is important if you want to showcase a cam , or your doing a review ..
Why I always try and compare to another cam ( direct comparison ) .. That way even if there is some youtube loss , the resulting video is still valid ..
But then Youtube is out of our control , so you just need to experiment and find a format that works best ...