Re: low-pass filter question
Re: low-pass filter question
- Subject: Re: low-pass filter question
- From: Antoine Missout <email@hidden>
- Date: Wed, 11 Jan 2006 11:11:31 -0500
You probably want to take a look at this.
http://www.audioease.com/Pages/BarbaBatch4/Barba4SRCTest.html
Antoine
On 11-Jan-06, at 2:30 AM, Rustam Muginov wrote:
Bill, does it use the same AULowPass? Or other filter?
What are the parameters for the filter? What are the characteristics?
I had also found what resampler build-in into OS X does not have
acceptable for our tasks characteristics.
Thank you.
--
Sincerely,
Rustam Muginov
On Jan 11, 2006, at 4:41 AM, William Stewart wrote:
The resampler does all of this filtering for you before it
resamples. You don't need to do anything else
Bill
On 10/01/2006, at 10:43 AM, Dan Morgan wrote:
I am working on an application where audio data is being sampled
at 48kHz. Because I am only interested in frequencies below
around 6-8kHz (and am interested in data reduction), I apply the
Apple low-pass filter audio unit with cutoff frequency 7kHz (to
prevent aliasing of frequencies above 8kHz) and then downsample
to 16kHz using a format converter. This should work fine if the
low-pass filter response is sharp.
The problem is that the Apple low-pass filter has a response that
is anything but sharp. I set up a little test program that
injected sine waves of different frequencies and found that
frequencies of half the cutoff were being significantly
attenuated and frequencies of double the cutoff had a significant
fraction passed. This is not acceptable behavior for the
intended application.
A couple questions: (1) Does the Apple format conversion have any
internal anti-aliasing low-pass filtering that it does when it
downsamples (hence making other low-pass filtering unnecessary)?
(2) If not, do you have any suggestions for how to proceed, e.g.
any other low-pass filters to consider?
Thanks.
_________________________________________________________________
Express yourself instantly with MSN Messenger! Download today -
it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/
direct/01/
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
40apple.com
This email sent to email@hidden
-- mailto:email@hidden
tel: +1 408 974 4056
_____________________________________________________________________
_____
"Much human ingenuity has gone into finding the ultimate Before.
The current state of knowledge can be summarized thus:
In the beginning, there was nothing, which exploded" - Terry
Pratchett
_____________________________________________________________________
_____
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
40spiritdsp.com
This email sent to email@hidden
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
@sonicbirth.com
This email sent to email@hidden
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden