Subband- and Wavelet-Based Coding - Digital Signal Processing: Fundamentals and Applications - page 634

% Analysis
sb_low ¼ filter(h0,1,speech); sb_high ¼ filter(h1,1,speech);
% Downsampling
sb_low ¼ sb_low(1:M:length(sb_low)); sb_high ¼ sb_high(1:M:length(sb_high));
% Quantization
%sb_low ¼ round((sb_low/2^15)*2^9)*2^(15-9); %Quantization with 10 bits
%sb_high ¼ round((sb_high/2^15)*2^5)*2^(15-5); % Quantization with 6 bits
% Synthesis
low_sp

zeros(1,M*length(sb_low)); % Upsampling
low_sp(1:M:length(low_sp))

¼

¼ sb_low;

high_sp ¼ zeros(1,M*length(sb_high)); high_sp(1:M:length(high_sp)) ¼ sb_high;

low_sp ¼ filter(g0,1,low_sp); high_sp ¼ filter(g1,1,high_sp);

rec_sig high_sp);

% Signal alignment for SNR calculations
speech ¼ [zeros(1,N-1) speech]; % Align the signal

¼ 2*(low_sp þ

↓ ↑

H 2 2

G 0

LL

↓ ↑

H 2 2

G 0

H ↓ ↑

G

2 2

1

xn ()

xn ()

LH

↓ ↑

H 2 2

G 0

HL

↑

H ↓ 2

G 2 1

↑

H ↓ 2 2

G 1

HH

Analysis stage

Synthesis stage

(a)

LL LH HH HL

0 /4 /2 3/4

(b)

FIGURE 13.12
Four-band implementation based on a binary tree structure.