Warning: Rank deficient, rank = 0... means what?

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Rick
Rick 2012-9-25
评论： Brandon Sackett 2020-11-18
Hi,
I am using the original signal FS and nbits. When i played the sound, it does have the speech, but its very noisy. I am currently doing this:
wavwrite(sig, Fs, nbits, 'Scrambled.wav');
i = 1;
k = 1;
siz = wavread('Scrambled.wav', 'size');
tot_samples = siz(1);
while(i<=tot_samples-15)
y = wavread('Scrambled.wav',[i i+15]);
ori_sig(:,k) = y\H;
if i == 1;
disp('Descrambling Speech in Progress...');
end
i = i+16;
k = k+1;
end
recon_sig = reshape(ori_sig,size(ori_sig,1)*size(ori_sig,2),1);
sound(recon_sig);
I have this warning: "Warning: Rank deficient, rank = 0, tol = 0.000000e+00."
What does it mean?
  2 个评论
Rick
Rick 2012-9-25
编辑：Rick 2012-9-25
These warnings were also shown when i tried to wavwrite:
Warning: Data clipped during write to file:Scrambled.wav
> In wavwrite>PCM_Quantize at 279
In wavwrite>write_wavedat at 301
In wavwrite at 138
In Speech_Scrambler at 29
What does it mean?
Rick
Rick 2012-9-26
编辑：Rick 2012-9-26
I used:
x(:,frame) = pinv(y\H, 0);
to solve my problem.
By doing this, I am keeping the same values for those values which are less than 0. But I am not sure whether is it the correct way. Any suggestion would be appreciated.

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采纳的回答

Wayne King
Wayne King 2012-9-25
编辑：Wayne King 2012-9-25
The inverse of a NxN matrix only exists only if the matrix has rank N. In other words, the linear operator that the matrix represents is surjective.
Computing the inverse in a computer has numerical subtleties. That warning is telling you that the matrix is rank deficient.
The wavwrite warning indicates that your signal values exceed +/- 1 and are being clipped when the .wav file is written. I don't think you want that clipping, that distorts the signal. You can scale the vector in MATLAB to make sure that the values do not exceed +/- 1 for writing.
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显示 4更早的评论
Rick
Rick 2012-9-25
编辑：Rick 2012-9-25
i see, than what does rank deficient matrix affects?
Brandon Sackett
Brandon Sackett 2020-11-18
Isn't a surjective solution valid though? I guess bijections are the "best" but is there a reason a surjective solution gets that warning? Any relation to group theory would help my brain understand the problem.

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更多回答（1 个）

Walter Roberson
Walter Roberson 2012-9-25
I can't tell what your "H" is there, but your "y" is all zero (or close to it) for 16 consecutive samples at some point.
The "clipped" indicates that you are attempting to write samples outside the range -1 to +1.
  1 个评论
Rick
Rick 2012-9-25
编辑：Rick 2012-9-25
H is a hadamard matrix of order 16.
Because i scrambled the signal using frame of 16 samples using:
y(:,k) = H*x;
k = k + 1;
I am now trying to descrambled it using 16 samples too by doing:
ori_sig(:,k) = y\H;
k = k + 1;
I know that clipping introduces distortion. Is there anyway where i can change the range of "y" to –1.0 <= y < +1.0, because I'm using 8 bits.

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