G.726 @ 32 kbps should be a lossless ADPCM transcoding of normal PCM G.711. I have listened to many codec and vocoder tests over the years and I could never hear the difference between PCM and ADPCM. I think that the 32k variant conveys all of the same data as uncompressed PCM. Nice thing is it runs at half the speed.
PCM (for those who don't know) samples the voice 8000 times a second and sends an 8 bit representation of the analog level of the audio at the time of the sample. That is how you get 64 kbps. (robbed bit signaling takes 1 bit out of every frame for signaling so many times we used to actually get 56kbps) The analog level codes are not linear, they are skewed to give more resolution at the lower audio levels in a process called companding. Companding significantly improves the signal to noise ratio. That is what they are referring to when they talk about mu law or A law PCM (or G.711). You have to have the right companding code selected or it will sound like UFOs have landed and are taking over. I have never been able to hear the difference between mu and A law companding either. A law was an international standard, mu law is used for US and Japan. ADPCM takes the same data of PCM and then transmits only the difference between samples, not the samples themselves. So, all the data is recovered but it requires a lower rate of transmission. There are variants of ADPCM that came along later to give even lower data rates. If you use G.726 make sure to select the 32 kbps if you are interested in keeping the voice quality up there. There is a 40 kbps option for G.726. I don't have a clue as to what it is about. ----- Original Message ----- From: "Mike Hammett" <[EMAIL PROTECTED]> To: "WISPA General List" <wireless@wispa.org> Sent: Monday, April 07, 2008 5:52 AM Subject: Re: [WISPA] Femtocells >I dunno if I'd use anything less than G.711. > > > ---------- > Mike Hammett > Intelligent Computing Solutions > http://www.ics-il.com > > > ----- Original Message ----- > From: "Chuck McCown - 2" <[EMAIL PROTECTED]> > To: "WISPA General List" <wireless@wispa.org> > Sent: Sunday, April 06, 2008 11:08 PM > Subject: Re: [WISPA] Femtocells > > >> G.711 require 64kbps plus overhead. Normally about 90 kbps. But there >> are >> lossless compression methods that can cut this in about half. >> ----- Original Message ----- >> From: "Marty Dougherty" <[EMAIL PROTECTED]> >> To: "'WISPA General List'" <wireless@wispa.org> >> Sent: Sunday, April 06, 2008 8:24 PM >> Subject: Re: [WISPA] Femtocells >> >> >>> Does anyone know how much BW a call will require? >>> >>> Marty >>> >>> -----Original Message----- >>> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On >>> Behalf Of Gino Villarini >>> Sent: Friday, April 04, 2008 5:57 AM >>> To: WISPA General List >>> Subject: Re: [WISPA] Femtocells >>> >>> Hmm I see better opportunity going to the Cellco directly and offer them >>> the >>> service, so that they do a bundle to the end user... Internet - >>> Femtocell >>> >>> And you make and arrangement with the cellco to deliver the traffic >>> directly >>> to them instead of going to the internet...Saving them some $$ On >>> Internet >>> Bandwidth and also providing a lower latency link to them!!! >>> >>> >>> ... maybe this is the next step beyond voip... >>> >>> Gino A. Villarini >>> [EMAIL PROTECTED] >>> Aeronet Wireless Broadband Corp. >>> tel 787.273.4143 fax 787.273.4145 >>> >>> -----Original Message----- >>> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On >>> Behalf Of George Rogato >>> Sent: Friday, April 04, 2008 6:30 AM >>> To: WISPA General List >>> Subject: [WISPA] Femtocells >>> >>> femtocells >>> >>> This is a great innovation that can help wisps gain market share. >>> >>> With these femtocells, the cell phone works in the house so the consumer >>> >>> doesn't need to have an extra land line. >>> The customer is probably paying 80.00 or so for their dsl - telephone >>> line. >>> No land line needed for us wisps, the customer's 80.00 telco package is >>> now >>> in "play". Maybe they want to trade it in for a faster and probably >>> lesser >>> expensive internet connection. >>> >>> It's a good opportunity for us, or the cable company. >>> >>> http://news.yahoo.com/s/ap/wireless_show_femtocells;_ylt=ArOpXSwLh8fh4Jp >>> nL.VHQpsjtBAF >>> >>> Verizon Wireless is joining Sprint Nextel Corp. in jumping on the latest >>> >>> craze in the wireless world: little boxes called femtocells that boost >>> cell-phone coverage in subscribers' homes. >>> >>> >>> >>> ------------------------------------------------------------------------ >>> -------- >>> WISPA Wants You! Join today! >>> http://signup.wispa.org/ >>> ------------------------------------------------------------------------ >>> -------- >>> >>> WISPA Wireless List: wireless@wispa.org >>> >>> Subscribe/Unsubscribe: >>> http://lists.wispa.org/mailman/listinfo/wireless >>> >>> Archives: http://lists.wispa.org/pipermail/wireless/ >>> >>> >>> ---------------------------------------------------------------------------- >>> ---- >>> WISPA Wants You! Join today! >>> http://signup.wispa.org/ >>> ---------------------------------------------------------------------------- >>> ---- >>> >>> WISPA Wireless List: wireless@wispa.org >>> >>> Subscribe/Unsubscribe: >>> http://lists.wispa.org/mailman/listinfo/wireless >>> >>> Archives: http://lists.wispa.org/pipermail/wireless/ >>> >>> >>> >>> -------------------------------------------------------------------------------- >>> WISPA Wants You! Join today! >>> http://signup.wispa.org/ >>> -------------------------------------------------------------------------------- >>> >>> WISPA Wireless List: wireless@wispa.org >>> >>> Subscribe/Unsubscribe: >>> http://lists.wispa.org/mailman/listinfo/wireless >>> >>> Archives: http://lists.wispa.org/pipermail/wireless/ >>> >> >> >> >> -------------------------------------------------------------------------------- >> WISPA Wants You! Join today! >> http://signup.wispa.org/ >> -------------------------------------------------------------------------------- >> >> WISPA Wireless List: wireless@wispa.org >> >> Subscribe/Unsubscribe: >> http://lists.wispa.org/mailman/listinfo/wireless >> >> Archives: http://lists.wispa.org/pipermail/wireless/ >> > > > > -------------------------------------------------------------------------------- > WISPA Wants You! 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