As such, the amount of data to be transfered can easily saturate USB 2.0 bus!įor example lets take a look at the 640x480 24bit RGB image captured at 30fps: The camera provides the highest quality image sensor data (uncompressed raw data). The PS3Eye is strictly a high-speed USB 2.0 device, meaning that if you have USB 1.0 port on your computer, the camera simply won't be able to transfer images to your machine. Lets take a look at some simple data transfer numbers. On the other hand, if you want to use this camera on your PC, you may possibly encounter some problems especially if the camera is shared with some other devices that reside on the same USB bus. This is all fine if you run the camera on your PS3 console. The camera data stream requires high transfer bandwidth that is more suitable for bulk transfers (uses all available USB bandwidth). The camera is designed to run on PS3 console for which Sony has a full control of both hardware and software. On the other hand, their decision is understandable because of the following: This is unfortunate, since as you saw these kinds of transfers do not provide any guaranteed latency or speed. The PS3Eye uses bulk transfers to send its image data to the USB host. Now, lets take a look at some of the design decisions Sony has made with their PS3Eye device. Control transfers - very short data transfers (often a few bytes) with guaranteed delivery, mainly used to send device control packets and receive the device status informationįrom the above information, you can see that the most suitable USB data transfer type for the camera type device is isochronous transfers. Bulk transfers - guarantees data delivery by using all available data bandwidth and large data transfers, but does not guarantee latency or transfer speed, mainly used by data storage devices Interrupt transfers - guarantees delivery latency time, but provides small data packet sizes, mainly used by keyboards, pointing devices and game controllers Isochronous transfers - guaranteed transfer speed (high priority), but not reliable delivery, mainly used by audio and video streaming devices. The USB 2.0 provides four data transfer types: In practice this number is lower due to some inherent USB communication overheads and it is more like two thirds of that number, so somewhere around 40MB/s. This new protocol was now able to transfer data at theoretical maximum of 60MB/s. The USB 2.0 was released in April 2000 and was standardized by the USB-IF at the end of 2001. While USB 1.0 was introduced in the early 1996 and it was able to transfer around 1.5MB/s, manufacturers soon realized that due to higher bandwidth requirements, the industry needed something better. Therefore, I wouldn't call it your typical a webcam. This device is made to be used in various real-time image processing and object tracking applications. Besides high resolution and image quality, this camera features unusually high frame capture rate for the device of this kind. This device is made to be used in various real-time image processing and tracking.
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