Invalid Audio File, too many samples

Hi all,

I have tried to implement the following codes:

     H = ones(16, 1);
     siz = wavread('hello.wav', 'size');
     tot_samples = siz(1);  %/ 74539 samples
     a=1;
     while(a<tot_samples)
        x = wavread('hello.wav', [a a+15]);  %/ read 16 samples each time
        y=H*x;                               %/ multiply together
        a = a + 16;
     end

     sound(y);                               %/ plays all the y

I keep getting "Invalid Wave File. Reason: Sample limits out of range." How can i get solve this error?

Also, after multiplying, how can i add up all the "y" and play it as a single audio file?

Answer 1

[Wayne King]

I'm not sure why you want to multiply by H here since it is just a vector or ones, but ok. I have a file called test.wav that has 20,000 samples and this works for me. I read 10 samples at time because 10 divides 20,000.

 H = ones(10,1);
 k = 1;
 a=1;
     while(a<=(tot_samples-9))
        x = wavread('test.wav', [a a+9]); 
        y(:,k) = H.*x;
        a = a+10;
        k = k+1;
     end

At the end of the loop I have a matrix, y, which is 10x2000. Note that 10*2000 is the length of the original signal. You can create the signal with:

sig = reshape(y,size(y,1)*size(y,2),1);

now sig and the original signal from the .wav are the same length and in this case, identical.

If course, you can preallocate y because you know going in what size the matrix will be.

[Rick]

I see, what if I now use:

H = hadamard(16);

I have to change the size of matrix "x" to 16 by 16?

or H to 16 by 1?

[Wayne King]

That very much depends on what you are trying to do with the Hadamard matrix, if you just want the matrix-vector product of each sequence with the matrix use.

y(:,k) = H*x;

[Rick]

I see, I am trying to achieve a speech scrambler with just

y =H*x;

where y is the output corresponding to the input, and x is the input in 16x1 speech vector.

EDIT:

i have put the output into a:

y(:,1) = H*x; %/ 1-channel

After the while loop:

i tried to listen to the output, all i have got is just a "tsk" sound. I believe that i am still listening to the last 15 samples of the output.

Is there anyway, where i can listen to the whole output instead of the last 15 samples?

[Wayne King]

Why are you doing it like this:

y(:,1) = H*x;

of course you are just getting the last samples, you simply keep replacing the first column of y with the latest H*x, that is why I did

 k = 1; % outside loop

and then

 y(:,k) = H*x; 
 k = k+1;
inside the loop.

then after the loop finished

 sig = reshape(y,size(y,1)*size(y,2),1);

[Rick]

I see, thanks for the enlightenment. :)

Answer 2

[Wayne King]

You cannot have the first sample being 0, MATLAB indexes from 1.

[Rick]

I see, I have changed it to start from 1. But i still getting the error:

"Error using wavread (line 164) Invalid Wave File. Reason: Sample limits out of range."

Is it because I have 74539 samples and I'm adding in frames of 16? so for the last frame, there is not enough samples in the wav file?

How can i solve this?

[Thomas]

look at the edits to my answer you have a couple of issues that are causing the problem..

[Wayne King]

It also stands to reason that you cannot have your a variable, a, get closer to the end of the file than 15 samples, so your terminating condition should be

 tot_samples-15

not while(a<tot_samples). And why did you pick a length that is not a divisor of the total file length?

[Rick]

I see.

Because I was given a project to use the given frame of 16 samples/frame.

Answer 3

[Thomas]

From, a cursory glance: you have initialized

i=0 There is no index of 0 in matlab and so it cannot play (0-15) range Also your way of calling ones is incorrect

try H=ones(16,1)

Try not to use 'i' as variable since it is in Matlab (complex function). In matlab the way to put comments is use '%' and not '*/'

EDIT

Also you are sampling upto tot_Sample when you have to until (tot-samples -15) otherwise you will run out of bounds again on the top end

[Rick]

I have changed to this:

   while(i<tot_samples-15)

but won't this code skip the last 15 samples of the file? I think I should put the code as follows:

while(i<=tot_samples-15)

so that i do not miss the last 15 samples.

Lastly, when i use:

sound(y);

i hear nothing. I assumed that it was because the y that i used was the last 15 samples of the audio file. How do i make it such that after every multiplication, the out is added to the previous output?

[Thomas]

your last iteration will go from

 i=tot_samples-15

to

 i+15

which is

 tot_samples-15 +15

(i.e. the end)

You donot hear anything because 15 samples is too small to hear

try

siz=wavread('hello.wav','size'); 
tot_samples = siz(1);  % 74539 samples
     i=1;
     for i=1:1000:tot_samples-1000
         i
        x = wavread('hello.wav', [i i+1000]);  % read 1000 samples 

             sound(x); 
       end

[Rick]

while(i<tot_samples-15) & while(i<=tot_samples-15) will not have a difference do they? Because, i increment in steps of 16.