User`s guide

Speech Record and Playback Demo

2.2.2 G.711 Speech Encoder and Decoder

The G.711 Encoder and Decoder implement the ITU-T G.711 Speech Compression

algorithm. This algorithm is an example of a waveform coder and provides a compres-

sion ratio of 2:1. The algorithm is implemented in G711.s and its interface is defined

by G711.h

2.2.3 Serial Flash Memory Driver

The Serial Flash Memory driver uses the SPI peripheral on the dsPIC33F device to

interface with the external serial Flash memory device. The driver requires a buffer for

its operation and this buffer must be allocated by the application. The driver allows the

application to perform operations such as read, chip erase, sector erase and status

check.

2.3 EXAMINING DEMO SOFTWARE FLOW

The Speech Record and Playback Demonstration application uses the WM8510

codec, G.711 speech encoding and decoding libraries, and the serial Flash memory

drivers to read, output and store speech signals with the starter kit. The application will

encode a microphone signal, store the encoded samples in serial flash memory and

play back the decoded samples to a headphone output. The G.711 μ-law algorithm is

used for encoding and decoding speech samples. Figure 2-2 and Figure 2-3 are flow

charts of the demo application.