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U. Glaeser

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characteristics:<br />

• Fixed pictures versus moving pictures (example: digital camera versus digital camcorder)<br />

• Picture production (camera) versus picture consumption (digital frame)<br />

• Portable versus semi-fixed/fixed equipment (example: digital camcorder versus webcam)<br />

• Equipment versus module (example: digital camera versus add-on to a palm-type device)<br />

Digital Camera<br />

A digital camera is made of several functions: an image sensor, a processing part, and a storage element.<br />

The processing includes three main algorithms, front-end processing, image compression (DCT is mainly<br />

used here), and coding (Huffman coding).<br />

In theory, a digital camera requires 10 DSP MIPS. Nevertheless, higher resolution, advanced algorithms<br />

(pixel by pixel) and sophisticated features such as the paparazzi effect turned the digital camera into a<br />

big DSP MIPS consumer. The paparazzi effect is when a series of pictures are taken at high speed (for<br />

example, 10 pictures in 1 s). In effect, we are not far from the performance of a video camera.<br />

Digital Video Camera (Camcorder)<br />

Big brother to the still camera, the video camera follows the same principle. It approximates the behavior<br />

of a digital camera except it has a better resolution and a continuous automatic stream of pictures. Another<br />

key difference is that it is a slave to the television set. Hence, decompression of pictures is as important<br />

as compression.<br />

Web Camera<br />

Not all video cameras need the sophistication of a camcorder. Common examples are surveillance cameras<br />

(slow speed, black and white) and Web cameras. The Webcam’s block diagram is very similar to a digital<br />

(still) camera except the storage function has been replaced by a modem. Because the speed of the network<br />

is the bottleneck, there is no need to take more than one or two pictures every 5 s. Note also that a Web<br />

camera does not need any decompression algorithms.<br />

PC Camera<br />

The PC is a $10 digital video camera put on top of PC and used for video telephony or college room<br />

broadcasting. Its consists of a very low sensor quality and a sub-dollar micro-controller. The PC has taken<br />

the role of a DSP.<br />

Modules and Toy Cameras<br />

In the same spirit, any host can take the DSP role. For instance, there is the case of digital camera modules<br />

(host independent), add-on to a PDA (palm OS is the host), and toy cameras (PC is host).<br />

Digital Picture Frame<br />

Not the most fascinating killer application of all times (sending baby pictures to grandparents), the digital<br />

picture frame is exactly the opposite of the Web camera. The image first goes through a modem function,<br />

then through decompression, and ends up its life on a picture frame display; however; contrary to a Web<br />

camera there are large problems due to the human interface and the way we (the grandparents) interact<br />

with this kind of device.<br />

PDAs (Handheld Devices, Palmtops)<br />

PDA is not (yet) a big DSP platform. Still serious inroads are made. Two common ones are the use of a<br />

PDA as a common platform for digital camera and MP3 player. Also Web access (necessitating a modem)<br />

and wireless access (obviously necessitating a wireless link) are the two good classical DSP applications,<br />

which are being pushed into these devices.<br />

© 2002 by CRC Press LLC

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