Waveform Quantization and Compression - Digital Signal Processing: Fundamentals and Applications - page 497

CHAPTER

11

Waveform Quantization and
Compression

CHAPTER OUTLINE

11.1 Linear Midtread Quantization ...................................................................................................... 497
11.2 m -law Companding ..................................................................................................................... 501
11.2.1 Analog m-Law Companding .....................................................................................501
11.2.2 Digital m-Law Companding......................................................................................504
11.3 Examples of Differential Pulse Code Modulation (DPCM), Delta Modulation,
and Adaptive DPCM G.721 .......................................................................................................... 509
11.3.1 Examples of Differential Pulse Code Modulation and Delta Modulation.......................509
11.3.2 Adaptive Differential Pulse Code Modulation G.721 .................................................512
Simulation Example..................................................................................................... 517
11.4 Discrete Cosine Transform, Modified Discrete Cosine Transform,
and Transform Coding in MPEG Audio .......................................................................................... 519
11.4.1 Discrete Cosine Transform......................................................................................519
11.4.2 Modified Discrete Cosine Transform ........................................................................522
11.4.3 Transform Coding in MPEG Audio ...........................................................................525
11.5 Laboratory Examples of Signal Quantization Using the TMS320C6713 DSK.................................... 528
11.6 Summary ................................................................................................................................... 533
11.7 MATLAB Programs ...................................................................................................................... 533

OBJECTIVES:
This chapter studies speech quantization and compression techniques such as signal companding,
differential pulse code modulation, and adaptive differential pulse code modulation. The chapter
continues to explore the discrete-cosine transform (DCT) and the modified DCT and shows how to apply the
developed concepts to understand the MP3 audio format. The chapter also introduces industry standards
that are widely used in the digital signal processing field.

11.1 LINEAR MIDTREAD QUANTIZATION
As we discussed in Chapter 2, in the digital signal processing (DSP) system, the first step is to sample and
quantize the continuous signal. Quantization is the process of rounding off the sampled signal voltage to
the predetermined levels that will be encoded by analog-to-digital conversion (ADC). We described the
quantization process in Chapter 2, in which we studied unipolar and bipolar linear quantizers in detail. In