Logitech Fusion Webcam

Hi Resolution Capture to Hard Drive - Speed Performance

by Gary Honis

UPDATE: 7.5 fps at 1280X960 rate achieved.See bottom of page for lossless compression codec to improve capture speed

TOUCAM: I have used the USB 1.1 Philips Vesta and Toucam webcams for a few years and writing AVI files to a hard drive has not presented any problems. I have heard of some webcam imagers having problems with faster frame rates and experiencing dropped frames. My computer and hard drive were always sufficient to capture large AVI files without problems or dropped frames when using the Toucam and Vesta.

FUSION: The USB 2.0 Logitech Fusion can provide higher resolution AVI files (1280X960) using third party software at both 5 frames per second (fps) and 7.5 fps. Below I explain my experience to date capturing the larger high resolution AVI files with the Fusion.

Data Transfer Rate Basics:

Some definitions to help explain bytes from bits, USB 1.1 from USB 2.0, kiloBytes vs. kilobits, etc....

USB Standards:
The USB 1.1 standard allows a theoretical maximum of 12 mbits per second.
The USB 2.0 standard allows a theoretical maximum of 480 mbits per second.

Bytes = (capital) B:
1 kB (one kiloByte) = 1,024 Bytes
1 mB (one megaByte) = 1,024 kB
1 gB (one gigaByte) = 1,024 gB

bits = (lower case) b:
1 kbps (one kilobit per second) = 1,000 bits per second
1 mbps (one megabit per second) = 1,000 kbps
1 gbps (one gigabit per second) = 1,000 mbps

K = 1,024
k= 1,000
1 Byte = 8 bits

(To keep things easy to follow I will mostly use bits and not Bytes in the discussion below)

USB 2.0:

Having a USB 2.0 device such as a webcam, does not mean that it will operate at the theoretical maximum USB 2.0 data transfer rate of 480 mbits per second. The actual performance of a USB 2.0 webcam will depend on the speed it can operate to take advantage of the USB 2.0 high speed data transfer connection. The actual performance will also depend on the speed of your processor and the sustained write speed of your hard drive. What kind of write speeds can you expect to achieve for high resolution imaging with a Logitech Fusion with your computer and its hard drive?

1280X960 Logitech Fusion Capture:

For the best quality image, no compression during capture is preferred. With the Fusion this means streaming to the hard drive uncompressed RGB24 color frames. One color RGB24 BMP frame is 28,800,000 bits (3,600,000 bytes as file size shown in Windows Explorer). With the Fusion frame capture rate set at 5 frames per second the data rate required for no dropped frames is (5 frames per second) X (28,800,000 bits per frame) = 144,000,000 bits per second or 144,000 kbps or 144 mbps. This can be a tremendous strain on your computer system and hard drive. This data rate would not be possible with a USB 1.1 connection or device which has a limitation of 12 mbits per second.

Keep in mind that a four minute AVI at high resolution and 5 fps uncompressed results in an AVI file that is over 4 GB in size!!

My Results:

At 1280X960 resolution and 5 fps setting for a four minute AVI capture, the Fusion with my external USB 2.0 hard drive is providing a 139 mbps data rate which results in a few dropped frames on my system at the 5 fps setting. An example is capturing 1127 frames out of 1200 total which I feel is an acceptable dropped frame loss.

My notebook is a Pentium 4 processor 2.4 GHz Toshiba. It has an internal 40GB Toshiba MK4018GAS hard drive that operates at 4200 rpm. I found that my two 250 GB USB 2.0 external hard drives have faster sustained write speeds than my internal drive. The external drives are 7200 rpm. You can test your hard drive speed using a number of free benchmark utilities. I have the sustained write speed specification for one of my external hard drives and it is 140 mbps.

I also tested the faster 7.5 fps setting at 1280X960 which is the fastest high resolution setting I have found available with third party capture software that works with the Fusion. I have been using OPEN VIDEO CAPTURE by DigitByte Studio. At the 7.5 fps setting, I found that there was no improvement in the actual capture rate which was still just under 140 mbps which appears to be the maximum sustained write speeds of my external hard drives. With the additional dropped frames at the 7.5 fps setting, the 5 fps setting actually worked better and provided a few more frames over the same 4 minute period for the AVI.

When an AVI capture begins, data is transferred from the webcam and computer to hard drive buffer. This buffer is relatively small but results in a fast transfer initially and the computer video display for monitoring goes smoothly during this period. Once the buffer is filled and tries to keep up with writes to the hard drive, the computer video gets choppy and eventually settles down with a screen refresh every few seconds.

I am shopping for another external hard drive with a faster sustained write specification to test if I can capture those extra 2.5 frames per second. Another option would be to use some type of compression but I would rather not go that route (Update: see lossless compression below).

The external USB 2.0 hard drives I am using:

USB 2.0 versus Firewire:

Based on test results of external USB 2.0 hard drives presently (1/06) on the market, the two hard drives I am using perform about average for data transfer rates and sustained write speeds. There are USB 2.0 hard drives that are testing a little better. I would expect USB 2.0 hard drive write speeds to continue to improve with time. Even though the theoretical maximum USB 2.0 data transfer rate is 480 mbps (57.2 MB/s) most hard drives are testing at speeds less than half the maximum. Some external hard drives have multiple connection types; USB 2.0, Firewire 400 and Firewire 800:

Theoretical Maxim data transfer rates:

 USB 2.0  480mbps
 FireWire 400  400mbps
 FireWire 800  800mbps

A good site for external hard drive reviews is ConsumerSearch.com. According to reviews referenced there, the hard drives that offer the fastest sustained write speeds for video are FireWire and not USB 2.0. Even though FireWire 400 has a theoretical maximum rate of 400 Mbps, which is less than 480 Mbps for USB 2.0, in comparison tests many Firewire 400 hard drives benchmark with faster data transfer rates than USB 2.0 drives. The hard drives providing the fastest data transfer rates are those with FireWire 800 connections.

Capture Software that provides high resolution modes for the Fusion:

Open Video Capture

IC Capture

Virtual Dub


Processing the Large AVI Files:

The large 4+ GB four minute AVI files being captured (for Saturn) can not be handled by the versions I have been using of Registax, K3CCDTools and Irfanview, for exporting of BMP files. What has been working for me is to open the 4 Gig AVI in Virtual Dub and then do a File/Save Image Sequence to export all the BMP frames. Then I load all the exported BMP frames into K3CCDtools....it accepts them all....and I continue processing from there.

UPDATE: Speed Increase By Using Lossless Compression:

I have tested a few lossless compression methods with both Open Video Capture and VirtualDub to determine if frame capture transfer rates could be improved. In particular, my notebook and external USB 2.0 hard drives could capture uncompressed AVI files at the maximum Fusion resolution of 1280X960 pixels at a frame rate of nearly 5.0 fps as discussed above. But the Fusion has the capability of a higher frame rate, 7.5 fps at the 1280X960 resolution and at that setting I would experience many dropped frames, bogging down the system and resulting in a frame rate less than 5.0 fps.

Lossless compression is used when it is important that the original and the decompressed data be identical "bit-for-bit", for the highest quality image. I tested the following free lossless compression codecs:





For my notebook and external hard drives, I obtained the fasted frame capture rates with the Huffyuv video codec. It is a very fast, lossless Win32 video codec written by Ben Rudiak-Gould. Using Huffyuv, I was able to capture at the maximum Fusion frame rate of 7.5 fps at the highest Fusion resolution of 1280X960. Problem solved!

With the Fusion frame capture rate set at 7.5 frames per second uncompressed and 1280X960 resolution, the data rate required for no dropped frames is (7.5 frames per second) X (28,800,000 bits per frame) = 216,000,000 bits per second or 216,000 kbps or 216 mbps. When the Huffyuv compression is used at this setting, there are no dropped frames and the resulting file is only 548,000 KB in size for a data transfer rate to the hard drive of 75,000 kbps or 75 mbps, a big reduction from 216 mbps. That is a sustained write speed my hard drives can easily handle.

A possible problem with using the Huffy video codec is that some video programs may not support it. I tested Huffy compressed AVI files with Open Video Capture, VirtualDub, Registax 3, K3CCDTools and IrfanView all worked well. I did have a problem opening Huffy compressed AVI files in Images Plus (vrs 1.72). To get around any compatibility problems, VirtualDub can be used to create a standard AVI file or to export frames as BMP files.

Using Open Video Capture with the Fusion for capturing AVI's, the following compression selection window appears (the Huffyuv compressor selection is shown):

Open Video Capture has a "Settings" button (in above image) for configuring settings of the video codec, but this "Settings" button does not work in Open Video Capture for the Huffyuv codec. Not to worry, there is another way to configure the Huffyuv settings. In Windows XP it takes a few steps as follows:

Select CONTROL PANEL, select SOUNDS AND AUDIO DEVICES, HARDWARE tab, select VIDEO CODECS, PROPERTIES button, PROPERTIES tab, selext HUFFYUV LOSSLESS CODEC [HFYU], PROPERTIES button and then the SETTINGS button. Whew!....this gets you to this window:

For my system, I found the above settings to give the fastest capture speed, so just set it.....and forget it:)

Based on the indoor testing I have done to date, the Huffyuv lossless compression codec works very well when the image has a lot of black (solid) color. When I increase the brightness of the image and use a very detailed object for the image, the Huffy compressor needs to work harder and the level of size compression is reduced. When imaging a planet, there is a lot of black color in the (outer) space around the planet so I expect the Huffyuv compression will work well. I expect that lunar imaging will put the Huffyuv compression to the test.

Check back for astro pics using the Huffyuv compressor.

Links to some of my previous pages on the Fusion:

For Part 1 of Fusion and Toucam comparison CLICK HERE.

For test image results using IC Capture Software that provides higher resolution video imaging CLICK HERE.

For Solar H-Alpha and Lunar test image results using IC Capture Software CLICK HERE.

Part 2 - Fusion and Toucam Compared - Saturn, Mars and Moon test images CLICK HERE.

Conversion instructions for Fusion Webcam CLICK HERE.

Animation & Images of Sun in H-Alpha CLICK HERE.

Jupiter & Saturn with Fusion settings and processing notes CLICK HERE.

3 hour Jupiter animation and images with Fusion settings and processing notes CLICK HERE.