which out of these two cables/ports is best for my miniDV camcorder?

[A complimentary Cc of this posting was sent to
John Navas
], who wrote in article :
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.]

E.g, see
http://groups.google.com/group/comp....761a99fc3c6a0d
and the thread.

Hope this helps,
Ilya

Ilya Zakharevich writes:
[A complimentary Cc of this posting was sent to
John Navas
], who wrote in article
:
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

[A complimentary Cc of this posting was sent to
Dave Martindale
], who wrote in article :
[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.

Sure. You could notice that this was already mentioned in the message
I replied to.

[I still hope I can spot a person who KNOWS the reasons for abysmal
performance of USB - comparing to Firewire...]

Yours,
Ilya

Ilya Zakharevich wrote:
[]
[I still hope I can spot a person who KNOWS the reasons for abysmal
performance of USB - comparing to Firewire...]

Yours,
Ilya

For your interest, here is a performance plot of a USB box being used in a
satellite data application:

http://www.david-taylor.myby.co.uk/mrtg/gemini_dvb.html

There is essentially no data loss (the data is checked and recorded), and
the daily data rate is measured at about 1.136MB/s. Unfortunately, one of
the data sources (a weather satellite) has been off the air just recently,
but the "weekly" graph shows a maximum data rate of about 1.8MB/s without
loss.

Many USB ports are still the lower speed, despite being labelled USB 2.0.
The do, of course, need to be "USB 2.0 hi-speed". On some older PCs, we
have also found older USB drivers being used, and not the "enhanced"
drivers, even though the port is 2.0 hi-speed. You do need to be careful.

Cheers,
David

[A complimentary Cc of this posting was NOT [per weedlist] sent to
David J Taylor
], who wrote in article :
[I still hope I can spot a person who KNOWS the reasons for abysmal
performance of USB - comparing to Firewire...]

For your interest, here is a performance plot of a USB box being used in a
satellite data application:

http://www.david-taylor.myby.co.uk/mrtg/gemini_dvb.html

I fail to see what may interest me in these graphs... I can get
sustained disk trasfer of up to 1MB/sec on USB1.1 (do not have much
stats with USB2 myself). No wonder one can do 80% more (on average)
on USB2. On the page, the maximum is claimed to be 12.5MB/sec, but
one can't see it from averaged graphs...

But if you know a device which can provide more than 33MB/sec
sustained (especially if you know WHY it performes better than other
devices), this would be very interesting...

Thanks anyway,
Ilya

Ilya Zakharevich wrote:
[A complimentary Cc of this posting was NOT [per weedlist] sent to
[]
http://www.david-taylor.myby.co.uk/mrtg/gemini_dvb.html

I fail to see what may interest me in these graphs... I can get
sustained disk trasfer of up to 1MB/sec on USB1.1 (do not have much
stats with USB2 myself). No wonder one can do 80% more (on average)
on USB2. On the page, the maximum is claimed to be 12.5MB/sec, but
one can't see it from averaged graphs...

But if you know a device which can provide more than 33MB/sec
sustained (especially if you know WHY it performes better than other
devices), this would be very interesting...

Thanks anyway,
Ilya

Actually, I am unsure of exactly what the maximum is for this particular
USB box. The other comments I made suggest why some systems may not
achieve the maximum USB 2.0 hi-speed throughput. For may applications, I
suspect that 1-3MB/s will be more that enough - it's already over 40GB per
day.

Cheers,
David

On Sat, 19 Jan 2008 07:41:03 +0000 (UTC), Ilya Zakharevich
wrote in :

[A complimentary Cc of this posting was sent to
Dave Martindale
], who wrote in article :
[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.

Sure. You could notice that this was already mentioned in the message
I replied to.

[I still hope I can spot a person who KNOWS the reasons for abysmal
performance of USB - comparing to Firewire...]

The primary issue, as I've noted previously, is not speed, but that
Firewire is designed for continuous independent bus transfers, whereas
USB 2.0 is not, with all USB transfers controlled by the host by means
of polling. That can result in small USB transfer pauses when the host
gets busy. (Ever notice how a USB mouse pointer will sometimes move
erratically?) This is no problem with, say, a disk drive, or even a DVD
burner (given underrun protection), but when digital video is being
streamed there's often no good way to pause the stream, so when the host
gets busy, data can be lost. USB 3.0 is supposed to address this issue,
but how well it will work in practice is an open question.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)

[A complimentary Cc of this posting was sent to
John Navas
], who wrote in article :
The primary issue, as I've noted previously, is not speed, but that
Firewire is designed for continuous independent bus transfers, whereas
USB 2.0 is not, with all USB transfers controlled by the host by means
of polling. That can result in small USB transfer pauses when the host
gets busy. (Ever notice how a USB mouse pointer will sometimes move
erratically?)

No. I do not see how the effect you describe can appear; device
drivers should not be affected by the "system being busy"; an
interrupt is an interrupt is an interrupt. I may be missing more
technical details...

Yours,
Ilya

Oh dear, where's the Geek to help you guys? :-)

OK, I'll be the Geek.

USB 2.0 (aka USB Hi-Speed) is technically faster (480Mbps) than Firewire 400
(400Mbps).

In real life USB maximum transfers peak at about 2/3 of that speed. If you
research actual test results, you'll often see speeds max out at 1/3 of the
max of 480 Mbps. Becasue USB creates a network where every device "chats'
with the central "host" (the computer in most cases) USB 2.0 requires more
CPU prcesses than Firewire and the more peripherals that are connected and
in use the slower the USB network. So avoid situations where you are
transferring from a USB device to a USB device (USB scanner to USB external
HD, USB camcorder to USB HD). Always transfer from a single USB device to a
non-USB device if possible. And don't forget that if you have a USB keyboard
and/or mouse connected you don't have a single device on the USB bus. Evbery
time you use the mouse or keyboard, you slow the network.

Firewire comes in two flavours. The original Firewire 400/IEEE1394(a) (100,
200, or 400 Mbps) and new Firewire 800/IEEE1394b (800Mbps). There's also a
'new' 3200 Mbps standard on the way. Actual speed is much closer to
technical speed, and faster and more reliable than USB. Why? Because of the
design. As well as significant design improvements that enhance and improve
efficiency through hardware implementation and control, Firewire allows each
device to control the network and each device can "speak" directly to
another without the need for a central "host". This significantly reduces
CPU load and increases transfer rates. Real life transfer rates on Firewire
are typically 90% of the max technical speed. Even poorly
configured/implemented Firewire can run at 80% of max speed.

Why Firewire is better than USB for Video:
As well as the significant real life speed improvement of Firewire over USB,
Firewire is also much better at sustained throughput, reducing (in fact in
most cases eliminating) dropped frames commonly seen in USB transfers.

A real test you can try:
Without doing anything else on the computer, transfer 5 minutes of video
using USB 2.0 and then Firewire and count the dropped frames. Now do it
again while using the computer (surf the net, type a letter, typical use
stuff). Now compare the droppped frames. I think you'll settle on Firewire.

Some sources:
http://en.wikipedia.org/wiki/USB
http://en.wikipedia.org/wiki/FireWire

[A complimentary Cc of this posting was sent to
Peter D
[email protected]], who wrote in article :
In real life USB maximum transfers peak at about 2/3 of that speed. If you
research actual test results, you'll often see speeds max out at 1/3 of the
max of 480 Mbps. Becasue USB creates a network where every device "chats'
with the central "host" (the computer in most cases) USB 2.0 requires more
CPU prcesses than

.... Sorry, but the *technical contents* of this is exactly 0. If you
know WHY the throughput is not close to the theoretical maximum,
please explain. If you do not - we all ALREADY know that it is not
close to the theoretical maximum; do you see any reason to repeat this
statement again?

Thanks,
Ilya