Hi Kevin, Luigi and others,<br>
Thanks for your discussion about this problem.<br>
<br>
Kevin/Luigi - Can you suggest me some open source implementation of "<span class="q">first order low-pass filter". <br>
I tried using </span><font size="2">libresample-0.1.3 and Secret Rabit
code. But they dont give me a clean API and are cryptic. Need to go
through all the code to understand their parameters they need and how
to set them. I am doing this at the moment, but if you have come across
some other library which can give me a cleaner interface, please
suggest.<br>
<br>
Thanks and Regards,<br>
Voipwala<br>
</font><br><div><span class="gmail_quote">On 11/17/05, <b class="gmail_sendername">Tony Mountifield</b> <<a href="mailto:tony@softins.clara.co.uk">tony@softins.clara.co.uk</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
In article <<a href="mailto:20051117024659.E88354@xorpc.icir.org">20051117024659.E88354@xorpc.icir.org</a>>,<br>Luigi Rizzo <<a href="mailto:rizzo@icir.org">rizzo@icir.org</a>> wrote:<br>> On Thu, Nov 17, 2005 at 10:28:47AM +0000, Tony Mountifield wrote:
<br>> ><br>> > The low-pass filter sounds complicated. How would that compare with, say,<br>> > taking the mean average of every six 48kHz samples to produce one 8kHz<br>> > sample?<br>><br>> it's just not the same thing and will give rise to all sort of
<br>> frequency aliasing effects - those that the lowpass filtering is supposed<br>> to remove.<br>> quick example: consider a 9khz signal - that is clearly not audible<br>> on a 4KHz channel (8000 hz sampling rate). Yet if you sample it at
<br>> 48khz and take the average of every 6 samples, these averages will not<br>> be constant (because the 9khz signal does not have a period of 6 samples)<br>> and so you'll get an output signal that will appear as 1KHz.
<br>> This is the aliasing effect.<br><br>That makes sense - thanks for the explanation!<br><br>Cheers<br>Tony<br>--<br>Tony Mountifield<br>Work: <a href="mailto:tony@softins.co.uk">tony@softins.co.uk</a> - <a href="http://www.softins.co.uk">
http://www.softins.co.uk</a><br>Play: <a href="mailto:tony@mountifield.org">tony@mountifield.org</a> - <a href="http://tony.mountifield.org">http://tony.mountifield.org</a><br>_______________________________________________
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