>>>>> "Greg" == Greg Herlein <gherlein@herlein.com> writes:Greg> I'm curious why not just sample at a lower rate [than 44kHz] Greg> if it's just VoIP anyway? There are audio cards and chipsets out there that only support 44k1. I'm sure that is the motivation. -JimC --- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'speex-dev-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.
> The cost of down-sampling, if done efficiently, is probably less then > the cost difference between 32 kHz and 44.1 kHz so it's probably worth > it. If you don't care about standard sampling rate, you could even to a > 2/3 conversion which would get you 29.4 kHz...I'm curious why not just sample at a lower rate if it's just VoIP anyway? My opinion is that 44kHz sampling for voice is excessive... unless you really do want to do CD quality. Greg --- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'speex-dev-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.
> I'm curious why not just sample at a lower rate if it's just VoIP > anyway? My opinion is that 44kHz sampling for voice is > excessive... unless you really do want to do CD quality.True, I think the best sampling rate for VoIP is probably 16 kHz. Jean-Marc -- Jean-Marc Valin, M.Sc.A. LABORIUS (http://www.gel.usherb.ca/laborius) Université de Sherbrooke, Québec, Canada <p> -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 242 bytes Desc: signature.asc Url : http://lists.xiph.org/pipermail/speex-dev/attachments/20030110/bd44754f/signature-0001.pgp
> > excessive... unless you really do want to do CD quality. > > True, I think the best sampling rate for VoIP is probably 16 kHz.Actually, if you are going to interface to the PSTN it's silly to sample at faster than 8kHz since that is what you will be limited to due to the legacy PSTN. Personally, I think you should evaluate the additional sound quality of sampling at 16kHz verses 8kHz against the fact that you are doubling your needed bandwidth when you do it. Two mode 3 compression streams sampled at 8kHz will use 8kbps each... add about 15% for packet overhead and you use about 35kbps for a two way conversation. You can easily fit that across a 64k link... doublign your sample rate to 16kHz would no longer let that same conversation fit across that link. It's a tradeoff. Greg <p>--- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'speex-dev-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.
Also some cards out there can only do full duplex if the sample rates are the same for playback and recording. -- Daniel, Epic Games Inc.> -----Original Message----- > From: owner-speex-dev@xiph.org [mailto:owner-speex-dev@xiph.org]On > Behalf Of James H. Cloos Jr. > Sent: Friday, January 10, 2003 7:42 PM > To: speex-dev@xiph.org > Subject: Re: [speex-dev] Optimizing speex for 44.1kHz > > > >>>>> "Greg" == Greg Herlein <gherlein@herlein.com> writes: > > Greg> I'm curious why not just sample at a lower rate [than 44kHz] > Greg> if it's just VoIP anyway? > > There are audio cards and chipsets out there that only support 44k1. > I'm sure that is the motivation. > > -JimC > > --- >8 ---- > List archives: http://www.xiph.org/archives/ > Ogg project homepage: http://www.xiph.org/ogg/ > To unsubscribe from this list, send a message to > 'speex-dev-request@xiph.org' > containing only the word 'unsubscribe' in the body. No subject is needed. > Unsubscribe messages sent to the list will be ignored/filtered. >--- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'speex-dev-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.