I have a watermarked signal WATERMARKED SIGNAL
And the actual watermark WATERMARK
In Matlab, I need to find out the delay parameters $d_i$ which can be considered as the embedded information.such that $0\leq d_i \leq 100$. There are 5 of them. I am afraid I don't understand the task, and my professor is on leave and will not be back before the task deadline. Would anyone be kind enough to at least tell me something about it? Show me a piece of code or a source? I can't seem to find any information about the code online.
EDIT: Thank you Mathew for the answer. Now I believe I know what to do mathematically but still can't achieve the answer I am required (This must come from the fact I am an amateur with Matlab). I tried to play with your code but I have no idea what I need to change in order for it to work. So I will show you the code I created and if you are still interested in helping me, could you tell me what else needs to be changed?
clear %Step 1. Upload sound files [x,fs] = audioread('sample4_va18535.wav'); [m,fs] = audioread('assignment4_embedded_signal.wav'); %Step 2. Determine number of samples and create the window N = 132300; w = blackman(N); %Step 3. Multiply both signals with the window to get x_w[n] and m_w[n] xw = x .* w; mw = m .* w; %Step 4. Apply FFT to get X_w(k) and M_w(k) XW = fft(xw); MW = fft(mw); %Step 5. Conjugate M_w(k) to get M_w*(k) MWconj = conj(MW); %Step 6. Normalize XW * M_w* Norm = abs(XW .* MWconj); %Step 7. Take IFFT xwmw = ifft((XW .* MWconj) ./ (Norm)); %Step 8. Plot everything (Using your method) lags = linspace(-N/2, N/2, N); figure(1); hold off; plot(lags,fftshift(abs(xwmw))) % find the 5 peaks, then plot them [pks,locs] = findpeaks(fftshift(abs(xwmw)),'NPeaks',5,'MinPeakHeight',0.0075); hold on; plot(lags(locs),pks,'rx'); xlabel('Correlation Lags'); ylabel('Scaled Correlation Magnitude (dB)') grid on; title('Watermark Cross-Correlation');
Thank you for being patient with me. And I will understand if you can't find time to help me more.