Can someone explain USB Transfer

[Mike Kujbida]

In theory, USB is faster than firewire.
The reality is that USB can’t maintain the speed necessary to capture full-frame full-motion (720×480 @ 30 fps.) video.
See the USB compared to FireWire page on Wikipedia for further information and links.

[Terje A. bergesen]

The reality is that USB can’t maintain the speed necessary to capture full-frame full-motion

This is incorrect, and I have a significant amount of video to prove it, but let us take a look at realities.

USB2 and FireWire has approximately the same theoretical maximum transfer rate, USB2 a little faster. In reality a USB transfer requires more support from the PC during transfers, so you will typically not get max peak transfer rates with USB. With a properly equipped PC (most PCs sold over the past 5 years are OK) you will have no problem transfering DV Video over a USB2 port. You will probably see more situations where you drop frames though, particularly if you are running stuff on your PC or something decides to kick in and do something. A USB transfer is far more sensitive to CPU activity than is a FireWire transfer.

There are very few camcorders that support DV capture over USB2. A notable exception is the Panasonic line of camcorders. You can transfer full DV over USB2 to your PC with these.

Software on the other hand is a whole different kettle of prawns. As of today I am only aware of one application that allows full DV capture over USB, and that is Windows Movie Maker.

The Microsoft USB capture drivers store the captured video in DV AVI files of Type 1. Most video editing software uses Type 2 (or was that the other way around, might have mixed them up). Anyway, assuming I am correct, Type 1 work well with Direct Show, but most video editing software is build around VfW, which is what you get with Type 2 AVIs. So if you capture with Movie Maker, your NLE might have problems reading your video files.

This all comes down to a single reality. In reality FireWire supports higher sustained speeds than does USB2. USB2 is also far more prone to drop frames due to activity on the host PC since USB2 requires a lot more CPU power to transfer data. This has lead the video world, sensibly, to standardize on FireWire. That is the reality. There are valid technical reasons for it, and if you want to do video you have to accept that reality. Simple as that.

[Mike Kujbida]

Thanks for correcting me Terje. Much appreciated.
Hopefully that answers Naiche’s questions.

[Naiche Lujan]

Thanks Terje and Mike for that information.
I appreciate the lucid explanation you gave Terje.
I really just needed to hear from someone, who has actually done this, what can be achieved with USB as that is the “easiest” way for me at this point.

I think my questions are almost answered, however, I should have been a little more forthright in my original post as to what the real application is for.

Perhaps this is a stretch for a predominantly digital forum, but I am trying to “digitize” Betacam SP video(tv broadcast quality analog) while retaining the maximum quality of the video. This is the ultimate goal. This should be 720×480 @ 30fps, but one also has to consider how the color is tranferred, etc. So, since I have yet to begin filming with dv, I thought I might be able to get away with a usb analog-to-digital converter, provided that it is not compressed in the transfer, or if so, only as much as raw dv. Also, I have to figure in Vegas or maybe I can use another program just for the importing if Vegas does not do good with USB connections.

So, would this change the way either of you would have answered the original post?

[Terje A. bergesen]

[Naiche Lujan] “So, would this change the way either of you would have answered the original post?”

No. In fact, it would make me even turn you towards a firewire solution. When you capture video like that, many solutions use your soundcard to encode the audio. You then have the USB and the sound card competing for CPU time, and I can almost guarantee that you will see delays in audio and mismatched audio and video.

If you want to digitize your old videos, go get a Canopus ADVC-110 or a 300, depending on your budget, and a firewire card. I spent time capturing VHS and stuff using other solutions and it wasn’t fun at all. Canopus is good and recommended.

And forget about USB, it is like to give you nightmares.