[asterisk-bugs] [Asterisk 0011796]: [patch] refactoring of fax tone detection in DSP

[noreply at bugs.digium.com]

A NOTE has been added to this issue. 
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http://bugs.digium.com/view.php?id=11796 
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Reported By:                dimas
Assigned To:                
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Project:                    Asterisk
Issue ID:                   11796
Category:                   PBX/General
Reproducibility:            always
Severity:                   feature
Priority:                   normal
Status:                     new
Asterisk Version:           SVN 
SVN Branch (only for SVN checkouts, not tarball releases):  trunk 
SVN Revision (number only!): 99085 
Disclaimer on File?:        N/A 
Request Review:              
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Date Submitted:             01-18-2008 20:36 CST
Last Modified:              01-31-2008 17:58 CST
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Summary:                    [patch] refactoring of fax tone detection in DSP
Description: 
Refactored DTMF digit detection, fax tone detection & added CED fax tone
detection. See Additional Infrmation for details.
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 dimas - 01-31-08 17:58  
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Ok, I think it is the last update.

Changed selection if Goertzel block size to prefer smaller blocks. There
are two reasons:
1. only if we have small enough block it is possible to squelch detected
tone from the voice data if we want later. (With large block it is not
possible because at the moment tone is detected, it is too late and lots of
frames with tone were already passed)
2. More importantly: it makes detection more reliable. This is because:
*) Larger block size allows less deviation of frequency
*) Testing with one of my fax machines i found it regularly produces some
clicking sounds which repeated multiple times within the large block makes
Goertzel energy for target frequency very low. With small block, that
"click" also makes code think there is no tone, but de-bouncing allows
these drop-outs in the middle of tone to be handled ok. 

Issue History 
Date Modified   Username       Field                    Change               
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01-31-08 17:58  dimas          Note Added: 0081551                          
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