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Bug 387364 - Standard OSC transpose intruduces aliasing
Standard OSC transpose intruduces aliasing
Status: RESOLVED FIXED
Product: beast
Classification: Other
Component: bse
SVN trunk
Other Linux
: Normal normal
: ---
Assigned To: Beast Maintainers
Beast Maintainers
Depends on:
Blocks:
 
 
Reported: 2006-12-19 01:08 UTC by Stefan Westerfeld
Modified: 2006-12-19 14:53 UTC
See Also:
GNOME target: ---
GNOME version: ---

Attachments
Example where aliasing can be heard (1.04 KB, text/plain)
2006-12-19 01:10 UTC, Stefan Westerfeld 		  Details
Patch which fixes the problem (1.26 KB, patch)
2006-12-19 13:48 UTC, Stefan Westerfeld 		none Details | Review

Description Stefan Westerfeld 2006-12-19 01:08:32 UTC 
The standard oscillator module of SVN r4184 prevents aliasing, if the frequency is set using the frequency property. However, if you set the frequency to something fixed (440), and then use the transpose property (set it to +40 or so), audible aliasing occurs.
Comment 1 Stefan Westerfeld 2006-12-19 01:10:17 UTC 
Created attachment 78607 [details]
Example where aliasing can be heard
Comment 2 Tim Janik 2006-12-19 01:14:31 UTC 
do you have a concrete suggestion to alter the current behavior?
Comment 3 Stefan Westerfeld 2006-12-19 13:48:38 UTC 
Created attachment 78622 [details] [review]
Patch which fixes the problem

This patch fixes the lookup for constant frequencies. I saw that the code already does the right thing when the oscillator frequency is an input signal, which is the more common usecase.
Comment 4 Tim Janik 2006-12-19 13:54:19 UTC 
great looks good. please apply. preferrably with a test case that catches/checks this change.
Comment 5 Stefan Westerfeld 2006-12-19 14:53:25 UTC 
(In reply to comment #4)
> great looks good. please apply.

Tue Dec 19 14:18:53 2006  Stefan Westerfeld  <stefan@space.twc.de>

        * gsloscillator.c: Take transpose factor into account for table
        lookups when the oscillator frequency is constant. Fixes #387364.

> preferrably with a test case that catches/checks this change.

Tue Dec 19 15:12:18 2006  Stefan Westerfeld  <stefan@space.twc.de>

        * tests/audio/Makefile.am:
        * tests/audio/osctranspose1.ref:
        * tests/audio/osctranspose1.bse:
        * tests/audio/osctranspose2.ref:
        * tests/audio/osctranspose2.bse: Added tests for the transpose
        property of BseStandardOsc. Should catch problems like #387364.