can anyone explain quantization index modulation code

i am trying to put watermark in an audio file...and i want to use quantization index modulation . iam trying to learn it through internet but i couldnt find any resources,,can anybody help me

Answer 1

[Hari]

Hi Vinay,

I understand that you are looking to embed a watermark in an audio file using Quantization Index Modulation (QIM).

In order to embed a watermark using QIM, you can follow the steps below:

Read the Audio File: Use the "audioread" function to load the audio file into MATLAB. This will give you the audio signal and its sampling frequency.

[audioData, fs] = audioread('your_audio_file.wav');

Prepare the Watermark:Create a binary watermark signal. Ensure that the watermark length is suitable for embedding into the audio signal.

watermark = randi([0, 1], 1, length(audioData)/100); % Example binary watermark

Quantization Index Modulation (QIM): Embed the watermark using QIM. You can quantize the audio samples and modulate them according to the watermark bits.

codedelta = 0.1; % Quantization step size
for i = 1:length(watermark)
    index = i * 100; % Example: Embed every 100 samples
    if watermark(i) == 0
        audioData(index) = delta * round(audioData(index) / delta);
    else
        audioData(index) = delta * (round(audioData(index) / delta) + 0.5);
    end
end

Save the Watermarked Audio:Use the "audiowrite" function to save the modified audio signal with the embedded watermark.

audiowrite('watermarked_audio.wav', audioData, fs);

Extract the Watermark (Optional):To verify the watermark, you can extract it by reversing the QIM process. Compare the quantized values to retrieve the watermark bits.

Refer to the documentation of "audioread" and "audiowrite" functions to know more about their properties:

• https://www.mathworks.com/help/matlab/ref/audioread.html
• https://www.mathworks.com/help/matlab/ref/audiowrite.html

Hope this helps!