Reply to Re: which out of these two cables/ports is best for my miniDV camcorder?

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Posted by Dave Martindale on 01/19/08 05:17

Ilya Zakharevich <nospam-abuse@ilyaz.org> writes:
>[A complimentary Cc of this posting was sent to
>John Navas
><spamfilter1@navasgroup.com>], who wrote in article
><eu22p3lk7aqqdu36a4k3pumqqd8iili4ar@4ax.com>:
>> It's probably more the issue of Firewire being designed for high-speed
>> independent transfers, whereas USB is controlled by host polling. See
>> my prior post to this thread.

>The conjecture I've heard on why USB2 is so much slower (in practice)
>than Firewire 400 is that current drivers/adapters do not use maximal
>possible buffer/window sizes.

>[AFAIK, maximal practically measured transfer rate of USB2 is
> 33MB/sec. This (was claimed to) coincides with the maximal
> theoretical transfer rate with some particlar small size of
> buffer/window.]

However, DV (and HDV) have a mean data rate of 25 Mbits/sec, or about 3
MBytes/sec. That's less than 10% of the measured 33 MB/sec, so
bandwidth should not be any more of a problem with USB2 than it is with
Firewire, at least on a USB2 controller that is not currently being used
by anything other than the video camera.

Dave

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