Chapter 1, INTRODUCTION Video Solutions, Audio Signal Processing and Coding

Problem 1

The objective of these introductory problems are to introduce the novice to simple relations between the sampling rate and the bit rate in PCM coded sequences.
Consider an audio signal, $s(n)$, sampled at $44.1 \mathrm{kHz}$ and digitized using a) 8-bit, b) 24-bit, and c) 32-bit resolution. Compute the data rates for the cases (a)-(c). Give the number of samples within a 16-ms frame and compute the number of bits per frame.

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Problem 2

The objective of these introductory problems are to introduce the novice to simple relations between the sampling rate and the bit rate in PCM coded sequences.
List some of the typical data rates (in $\mathrm{kb} / \mathrm{s}$ ) and sampling rates (in $\mathrm{kHz}$ ) employed in applications such as a) video streaming, b) audio streaming, c) digital audio broadcasting, d) digital compact cassette, e) MiniDisc, f) DVD, g) DVD-audio, h) SACD, i) MP3, j) MP4, k) video conferencing, and 1) cellular telephony.

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Problem 3

The objective of this exercise is to familiarize the reader with the handling of sound files using MATLAB and to expose the novice to perceptual attributes of sampling rate and bit resolution.
For this computer exercise, use MATLAB workspace ch1pb1.mat from the website.
Load the workspace ch1pb1.mat using,
> load('ch1pb1.mat');
Use whos command to view the variables in the workspace. The data-vector 'audio_in' contains 44,100 samples of audio data. Perform the following in MATLAB:
>> wavwrite(audio_in,44100,16, 'pb1_aud44_16.wav') ;
>> wavwrite (audio_in,10000,16, 'pb1_aud10_16.wav');
>> wavwrite(audio_in,44100,8, 'pb1_aud44_08.wav');
Listen to the wave files $p b 1_{-} a u d 44 \_16 . w a v, p b 1 \_a u d 10 \_16 . w a v$, and pb1_aud44_08.wav using a media player. Comment on the perceptual quality of the three wave files.

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Problem 4

The objective of this exercise is to familiarize the reader with the handling of sound files using MATLAB and to expose the novice to perceptual attributes of sampling rate and bit resolution.
Down-sample the data-vector 'audio_in' in problem 1.3 using
>> aud_down_4 = downsample(audio_in, 4);
Use the following commands to listen to audio_in and aud_down_4. Comment on the perceptual quality of the data vectors in each of the cases

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