bugGNU Octave - Bugs: bug #45807, problem with specgram function

 
 

bug #45807: problem with specgram function

Submitter:  Ernotte Pierre <ernottep>
Submitted:  Fri 21 Aug 2015 01:59:35 PM UTC
   
 
Category:  Octave Function Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Incorrect Result
Status:  Duplicate Assigned to:  None
Originator Name:  ernottep Open/Closed:  * Closed
Release:  * 3.8.1 Operating System:  * GNU/Linux
Fixed Release:  None Planned Release:  None
* Mandatory Fields

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Fri 21 Aug 2015 02:15:46 PM UTC, comment #1: 

Thanks for the detailed report. This is actually a bug in Octave version 3.8.1 and was fixed in the 3.8.2 update and later. Please update your version of Octave if possible to take advantage of this fix (bug #42043).

Mike Miller <mtmiller>
Group Member
Fri 21 Aug 2015 01:59:35 PM UTC, original submission:  

The following code give a bad result found as attached field:

x = chirp([0:0.001:2],0,2,500);#freq. sweep from 0-500 over 2 sec.
Fs=1000;            # sampled every 0.001 sec so rate is 1 kHz
step=ceil(20*Fs/1000);    # one spectral slice every 20 ms
window=ceil(100*Fs/1000); # 100 ms data window
specgram(x, 2^nextpow2(window), Fs, window, window-step);

**********************************************************
I obtain the same result with the following code:

[S,f,t]=specgram(x, 2^nextpow2(window), Fs, window, window-step);
S=abs(S);
figure;imagesc(t,f,S)

***********************************************************
I obtain the good result with the code

figure;imagesc(S)

***********************************************************
I use signal-1.3.2

Ernotte Pierre <ernottep>

 

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Attached Files
file #34688:  specgram_bug.pdf added by ernottep (5KiB - application/force-download)
file #34687:  specgram_bug.pdf added by ernottep (5KiB - application/force-download)

 

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    Follow 6 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2015-08-21 mtmiller StatusNone Duplicate
        Open/ClosedOpen Closed
        Dependencies- Depends on bugs #42043
    2015-08-21 ernottep Attached File- Added specgram_bug.pdf, #34688
    2015-08-21 ernottep Attached File- Added specgram_bug.pdf, #34687
        Carbon-Copy- Added ernottep

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