To get an idea of the number of bits generated and processed by a digital system consider the following applications:

(a) A compact disk (CD) is capable of storing 75 min of “CD quality” stereo (left and right channels are recorded) music. Calculate the number of bits that are stored in the CD as raw data. (b) Find out what the vocoder in your cell phone is used for. To attain “telephone quality” voice you use a sampling rate of 10,000 samples/sec,and that each sample is represented by 8 bits. Calculate the number of bits that your cell-phone has to process every second that you talk. Why would you then need a vocoder?

(c) Find out whether text messaging is cheaper or more expensive than voice. Explain how the text messaging works.

(d) Find out how an audio CD and an audio DVD compare. Find out why it is said that a vinyl long-play record reproduces sounds much better. Are we going backwards with digital technology in music recording? Explain.

(e) To understand why video streaming in the internet is many times of low quality, consider the amount of data that needs to be processed by a video compressor every second. Assume the size of a video frame, in pixels, is 352 × 240, and that an acceptable quality for the image is obtained by allocating 8 bits/pixel and to avoid jerking effects we use 60 frames/second.

• How many pixels need to be processed every second?

• How many bits would be available for transmission every second?

• The above is raw data, compression changes the whole picture (literally), find out what some of the compression methods are.