This project consist of audio compression technology using matlab in which we use haar wavelets algorithm.
This code performs wavelet compression over a .wav file.The scheme is a simplified version of the one described on the paper "low bit rate" transparent audio compression using adapted wavelets.
NOTE: The file must be in the same folder where this file is located.If you want to try this scheme with other audio file, please change the name of the cariable "file".avoid using long audio files or long silences at the beginning of the file for computational constraints.
clear;clc; file='Coltrane.wav'; wavelet='dB10'; level=5; frame_size=2048; psychoacoustic='on '; %if it is off it uses 8 bits/frame as default wavelet_compression = 'on '; heavy_compression='off'; compander='on '; quantization ='on '; %%%%%%%%%%%%%%%%%%%%%%%%% % ENCODER % %%%%%%%%%%%%%%%%%%%%%%%%% [x,Fs,bits] = wavread(file); xlen=length(x); t=0:1/Fs:(length(x)-1)/Fs; %decomposition using N equal frames step=frame_size; N=ceil(xlen/step); %computational variables Cchunks=0; Lchunks=0; Csize=0; PERF0mean=0; PERFL2mean=0; n_avg=0; n_max=0; n_0=0; n_vector=[]; for i=1:1:N if (i==N) frame=x([(step*(i-1)+1):length(x)]); else frame=x([(step*(i-1)+1):stepi]); end %wavelet decomposition of the frame [C,L] = wavedec(frame,level,wavelet); %wavelet compression scheme if wavelet_compression=='on ' [thr,sorh,keepapp] = ddencmp('cmp','wv',frame); if heavy_compression == 'on ' thr=thr10^6; end [XC,CXC,LXC,PERF0,PERFL2] = wdencmp('gbl',C, L, wavelet, level,thr,sorh,keepapp); C=CXC; L=LXC; PERF0mean=PERF0mean + PERF0; PERFL2mean=PERFL2mean+PERFL2; end %Psychoacoustic model if psychoacoustic=='on ' P=10.log10((abs(fft(frame,length(frame)))).^2); Ptm=zeros(1,length(P)); %Inspect spectrum and find tones maskers for k=1:1:length(P) if ((k<=1) | (k>=250)) bool = 0; elseif ((P(k)<P(k-1)) | (P(k)<P(k+1))), bool = 0; elseif ((k>2) & (k<63)), bool = ((P(k)>(P(k-2)+7)) & (P(k)>(P(k+2)+7))); elseif ((k>=63) & (k<127)), bool = ((P(k)>(P(k-2)+7)) & (P(k)>(P(k+2)+7)) & (P(k)>(P(k- 3)+7)) & (P(k)>(P(k+3)+7))); elseif ((k>=127) & (k<=256)), bool = ((P(k)>(P(k-2)+7)) & (P(k)>(P(k+2)+7)) & (P(k)>(P(k- 3)+7)) & (P(k)>(P(k+3)+7)) & (P(k)>(P(k-4)+7)) & (P(k)>(P(k+4)+7)) & (P(k)>(P(k-5)+7)) & (P(k)>(P(k+5)+7)) & (P(k)>(P(k-6)+7)) & (P(k)>(P(k+6)+7))); else bool = 0; end if bool==1 Ptm(k)=10log10(10.^(0.1.(P(k1)))+10.^(0.1.(P(k)))+10.^(0.1.P(k+1))); end end sum_energy=0;%sum energy of the tone maskers for k=1:1:length(Ptm) sum_energy=10.^(0.1.(Ptm(k)))+sum_energy; end E=10log10(sum_energy/(length(Ptm))); SNR=max(P)-E; n=ceil(SNR/6.02);%number of bits required for quantization if n<=3%to avoid distortion by error of my psychoacoustic model. n=4; n_0=n_0+1; end if n>n_max n_max=n; end n_avg=n+n_avg; n_vector=[n_vector n]; end %Compander(compressor) if compander=='on ' Mu=255; C = compand(C,Mu,max(C),'mu/compressor'); end %Quantization if quantization=='on ' if psychoacoustic=='off' n=8;%default number of bits for each frame - sounds better but uses more bits end partition = [min(C):((max(C)-min(C))/2^n):max(C)]; codebook = [min(C):((max(C)-min(C))/2^n):max(C)]; [index,quant,distor] = quantiz(C,partition,codebook); %find and correct offset offset=0; for j=1:1:N if C(j)==0 offset=-quant(j); break; end end quant=quant+offset; C=quant; end %Put together all the chunks Cchunks=[Cchunks C]; %NOTE: if an error appears in this line just modify the transpose of C Lchunks=[Lchunks L']; Csize=[Csize length(C)]; Encoder = round((i/N)100) %indicator of progess end Cchunks=Cchunks(2:length(Cchunks)); Csize=[Csize(2) Csize(N+1)]; Lsize=length(L); Lchunks=[Lchunks(2:Lsize+1) Lchunks((N-1)Lsize+1:length(Lchunks))]; PERF0mean=PERF0mean/N %indicator PERFL2mean=PERFL2mean/N %indicator n_avg=n_avg/N%indicator n_max%indicator end_of_encoder='done'%indicator of progess %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% In this part the signal is stored with the new format or transmitted by frames This new format uses this parameters: header: N, Lsize, Csize. body: Lchunks (small), Cchunks(smaller signal because now it is quantized with less bit and coded) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%% % DECODER % %%%%%%%%%%%%%%%%%%%%%%%%% %reconstruction using N equal frames of length step (except the last one) xdchunks=0; for i=1:1:N if i==N Cframe=Cchunks([((Csize(1)(i-1))+1):Csize(2)+(Csize(1)(i- 1))]); %Compander (expander) if compander=='on ' if max(Cframe)==0 else Cframe = compand(Cframe,Mu,max(Cframe),'mu/expander'); end end xd = waverec(Cframe,Lchunks(Lsize+2:length(Lchunks)),wavelet); else Cframe=Cchunks([((Csize(1)(i-1))+1):Csize(1)*i]); %Compander (expander) if compander=='on ' if max(Cframe)==0 else Cframe = compand(Cframe,Mu,max(Cframe),'mu/expander'); end end xd = waverec(Cframe,Lchunks(1:Lsize),wavelet); end xdchunks=[xdchunks xd]; Decoder = round((i/N)*100) %indicator of progess end xdchunks=xdchunks(2:length(xdchunks)); distorsion = sum((xdchunks-x').^2)/length(x) end_of_decoder='done' %creating audio files with compressed schemes wavwrite(xdchunks,Fs,bits,'output.wav') %this does not represnet the real compression achieved. It is only to hear the results end_of_writing_file='done'%indicator of progess