Tuesday, February 21, 2006

Video Transfer: USB vs Firewire

A customer arrived in today with a problem transferring video from his DV camera to his PC without stuttering. The camera in question was a Samsung VP-D453, which seems a nice little unit, and he was using a USB cable to transfer the video to the PC. My experience with video transfer to date has been with Firewire (IEEE 1394) and I wasn't sure what to expect when using a USB cable so I dug around the web see how USB measured up to the task and garnered the following:

"In the not too distant past, there was a clear distinction between USB and FireWire. USB 1.1 could not transfer high quality DV; loosely defined as 25 frames per second (fps) with each frame being 640x480 resolution, due to USB's transfer limit of around 11Mbps (or around 1.5MB per second). Transferring DV requires a transfer rate of at least 3.6MB per second, which left FireWire as the only option due to its ability to work at 400Mbps, or up to around 50MB per second. Then along came USB 2.0 with a transfer rate of 480Mbps or around 60MB per second.

At first glance it would appear that USB 2.0 is even faster than FireWire; however speed is not the only issue when it comes to DV. One serious issue with USB 2.0 is that it can not guarantee a specified data transfer rate. This is due to USB 2.0 being a master-slave technology, which means it needs a computer's CPU to coordinate the appropriate data transfers. While not a problem when dealing with low demand peripherals such as Web cams, scanners, printers etc, digital video requires dependable performance to avoid dropping video frames.

FireWire is a much more independent technology in that it works in a peer-to-peer relationship. For this reason, many professional DV users are now able to download their video from a DV camcorder to an external hard drive without the use of a PC. Finally, and most importantly, FireWire delivers data consistently at a specific rate. If you want to work with video, even to edit the family movie, go with FireWire."

My experience with the customer's camera seemed to bear this out when we did some trials using one of our workshop machines. Firewire, in addition to allowing the camera transport mechanism to be controlled from the PC, gave the best quality picture with no stuttering in evidence.

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