Lately, it seems that my downloading from sites had slowed in general.

I have been downloading college lectures from youtube. In the past month or two, it seems the download speed has dropped dramatically. But I discovered that download speed of flv files was about 40-60kbs.
When I started using mp4 format, I could get downloads at the rate of 110-160 kbs. (In the past, 160kbs had been about the max I was getting downloading anything such as video files or iso files for the latest, greatest linux distro).

Can anybody explain why mp4 downloads so much faster than flv?

I was beginning to think my IP was throttling me. Advertised download is 1.5mbs for my dsl ip.

Thanks.