From: Sebastian Kaliszewski <Sebastian.Kaliszewski@softax.com.pl>
To: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] PC speaker emulation (square wave)
Date: Thu, 26 Jan 2006 17:55:40 +0100 [thread overview]
Message-ID: <43D8FF0C.5020903@softax.com.pl> (raw)
In-Reply-To: <ED00D612-2AD2-4BE8-AC9A-585C70F4660D@gmx.de>
Joachim Henke wrote:
> Ok, I simplified my patch to generate just plain square waves. Indeed,
> its sound is much closer to a real PC speaker now.
>
> Does "cut off frequency" mean, that we have silence above that specific
> frequency?
No. Typical cutoff freq is where components of the signal are attenuated by
3dB (i.e. are half as loud). At 2 times taht frequency they'll be attenuated
by 3 + A dB, where A is filter's rate in dB/octave. Typical 1st order filter
is 6dB/octave, 2nd order is 12dB/octave, etc. Typical soundards used no more
than 2nd order filter.
But, if you want to have your path behave really nicely, you should simply
not generate at all waves at frequencies above half of current output
sampling rate -- those can't be reproducted -- instead significant
distortion will be generated (google for Nyquist frequency).
rgds
--
Sebastian Kaliszewski
next prev parent reply other threads:[~2006-01-26 16:43 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-01-09 19:01 [Qemu-devel] [patch] minimal PC speaker output Joachim Henke
2006-01-09 20:40 ` Fabrice Bellard
2006-01-10 9:11 ` he.jo
2006-01-18 23:05 ` [Qemu-devel] [PATCH] PC speaker emulation Joachim Henke
2006-01-18 23:32 ` [Qemu-devel] " Joachim Henke
2006-01-19 0:32 ` [Qemu-devel] " malc
2006-01-19 20:44 ` [Qemu-devel] [PATCH] PC speaker emulation (fixed) Joachim Henke
2006-01-19 23:29 ` malc
2006-01-20 9:42 ` Joachim Henke
2006-01-20 13:03 ` Johannes Schindelin
2006-01-20 12:03 ` Sebastian Kaliszewski
2006-01-23 21:10 ` [Qemu-devel] [PATCH] PC speaker emulation (fixed point) Joachim Henke
2006-01-24 12:35 ` Sebastian Kaliszewski
2006-01-24 15:50 ` Joachim Henke
2006-01-24 18:29 ` Sebastian Kaliszewski
2006-01-24 21:45 ` Fabrice Bellard
2006-01-25 0:38 ` Sebastian Kaliszewski
2006-01-25 21:54 ` [Qemu-devel] [PATCH] PC speaker emulation (square wave) Joachim Henke
2006-01-26 4:50 ` Jamie Lokier
2006-01-26 16:55 ` Sebastian Kaliszewski [this message]
2006-01-29 10:44 ` Joachim Henke
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