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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=kkyzivat@tripleplayint.com
href="mailto:kkyzivat@tripleplayint.com">Keith Kyzivat</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=vincent.burel@vb-audio.com
href="mailto:vincent.burel@vb-audio.com">Vincent Burel</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Cc:</B> <A title=Alexander.Chemeris@sipez.com
href="mailto:Alexander.Chemeris@sipez.com">Alexander Chemeris</A> ; <A
title=speex-dev@xiph.org
href="mailto:speex-dev@xiph.org">speex-dev@xiph.org</A> ; <A
title=jean-marc.valin@usherbrooke.ca
href="mailto:jean-marc.valin@usherbrooke.ca">Jean-Marc Valin</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, November 14, 2008 3:34
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Speex-dev] SPEEX on iPhone
?</DIV>
<DIV><BR></DIV><BR><BR>
<DIV class=gmail_quote>On Fri, Nov 14, 2008 at 3:57 AM, Vincent Burel <SPAN
dir=ltr><<A
href="mailto:vincent.burel@vb-audio.com">vincent.burel@vb-audio.com</A>></SPAN>
wrote:<BR>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<DIV class=Ih2E3d>> Speech compression algorithms always are tunned to
particular freq,<BR></DIV>
<DIV class=Ih2E3d>> else they would take tons of time. That's because
they use knowledge<BR>> that speech pitch (and other params) lies in well
specified regions.<BR>> Thus if you feed algorithm with wrong freq,
you'll fool it and it might<BR>> even not detect speech at
all.<BR><BR></DIV>Do you mean that speex is working at 44.1 Khz like at
32Khz without<BR>samplerate conversion ?<BR><BR>It seems you suggest that
working with 44.1 Khz signal instead of 32Khz<BR>(wich is the native
samplingrate for the ultra -wide-band mode as far as i<BR>understand) ask
for more CPU load. Since YOU have already worked with SPEEX,<BR>do you know
how much CPU load it takes ? 10% more ? 50% more ?</BLOCKQUOTE>
<DIV><BR></DIV>
<DIV>Standard sample rate used with speex is 8kHz.</DIV>
<DIV>Speex wideband uses 16kHz</DIV>
<DIV>Speex ultra-wideband uses 32kHz</DIV>
<DIV><BR></DIV>
<DIV>Many speech applications use use just the standard 8kHz speex mode.</DIV>
<DIV><BR></DIV>
<DIV>What Alex is saying is, you'll (probably) want to record from sound card
at 44.1kHz or 48kHz (depending on native rate of sound card-- which isn't
always easy to find out), then use a software resampler like speexdsp provides
(but any implementation will do) to resample the data down to your target
sample rate for speex (8kHz for standard speex, 16kHz for wb, 32kHz for uwb).
Then push it through speex routines, send it where it needs to be,
decode with speex routines, then resample it back up to 44.1/48kHz, and play
it out at the destination end.</DIV>
<DIV><BR></DIV>
<DIV>This of course, presumes that your audio source and sink are provided by
the myriad of sound cards that have been designed for Windows, and are
supported by other OSes.</DIV>
<DIV>Basically, sound cards these days are designed to work with only one or
two sample rates, and their drivers do the resampling to get it to
target/destination sample rate. Quite a few years back (so some google
research suggests), Microsoft disseminated some faulty resampling reference
code that just got integrated with a lot of sound card drivers, and exists to
this day (so they say -- take this with a grain of salt though). One
thing I can be sure of (I have seen), is that if you resample the data to the
sound card's native sample rate (which, I think it can be safe that most all
sound cards use 48kHz or 44.1kHz), latency (definitely) and jitter(maybe?)
goes down pretty significantly.</DIV></DIV></BLOCKQUOTE>
<DIV><BR>
<DIV><FONT size=2>Well, thanks for your reply about sound card... but it was not
really the question. First, i remind that i already use SPEEX at 44.1
Khz without converting signal to native 32Khz, and it works very well. So now i
would like to get reply to my both original questions if possible :</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>1- Does SPEEX is doing the down/upsampling when working with
44.1Khz signal or does it process this signal as it was 32Khz ?</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>1- if i setup SPEEX in 32Khz and do the down/upsampling
myself, what does it bring ? better quality ? much CPU performance ? how much
?</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Thanks by advance.</FONT></DIV>
<DIV><FONT size=2>Regards </FONT></DIV>
<DIV><FONT size=2>Vincent Burel</FONT></DIV></DIV></BODY></HTML>