DSP Final Project

Digital audio signal compression based on ADPCM and Huffman encoding

Adviser: 陳祝嵩 教授Speaker: 劉宛靈學號 :R95942118

Motivation

People nowadays attach importance to compression technique. To reduce files’ size so that one channel could

transmit more files. Your USB flash drive can save more songs.

Introduction

I use ADPCM to do the first compression and then do the second compression with Huffman encoding.

Observe the compression ratio of the compressed data and audio’s performance.

ADPCM (Adaptive Differential Pulse Code Modulation )

ADPCM is a variant of DPCM that varies the size of the quantization step, to allow further reduction of the required bandwidth for a given SNR.

4-bit ADPCM

Huffman encoding (1/2)

entropy encoding algorithm lossless data compression the file is searched for the most frequently ap

pearing symbols and then a tree is build that replaces the symbols by shorter bit sequences.

Huffman encoding (2/2)

a(4500),b(1300),c(1200),

d(1600),e(900),f(500)Then the final Huffman tree would be: ( right side figure)

The final codes would be:

A:0B:101C:100D:111E:1101F:1100

Achievement

Using C++ programming language to realize this method of audio compression.

Observe compressed audio quality if the compression causes serious loss.

Reference

“A high-efficiency speech coding algorithm based on ADPCM with multi-quantizer ”by Taniguchi, T.; Iseda, K.; Unagami, S.; Tominaga, S.;Acoustics, Speech, and Signal Processing, IEEE International Conference on ICASSP '86.Volume 11,  Apr 1986

“Sampled-data audio signal compression with Huffman coding” by Ashida, S.; Kakemizu, H.; Nagahara, M.; Yamamoto, Y.;SICE 2004 Annual Conference Volume 2,  4-6 Aug. 2004