Dear all, I have an Asterisk SIP server in a LAN environment and I want your opinion in order to decide the use of an audio codec: What audio codec is better, G.711a or G.711u ??? Which suites to my LAN voip calls ??? Thank you !!! Alejandro -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.digium.com/pipermail/asterisk-users/attachments/20100323/da2eea19/attachment.htm
On 24/03/10 8:41 AM, Alejandro Cabrera Obed wrote:> Dear all, I have an Asterisk SIP server in a LAN environment and I want > your opinion in order to decide the use of an audio codec: > > What audio codec is better, G.711a or G.711u ??? Which suites to my LAN > voip calls ???It basically comes down to where the system is being used and what codecs you're using upstream. G.711a is aLaw and G.711u is uLaw. uLaw is predominantly used in the USA. aLaw is used in most of the rest of the world (although I think Japan might use uLaw). If you're using an ISDN card then it will be talking aLaw or uLaw depending on where you are. The idea is to avoid transcoding - i.e. converting between one format and another. So, if you're using a VoIP provider instead of ISDN, it will depend on what they're using. If your VoIP provider is outside of the US and accepts aLaw, then that's likely what you want to use (bear in mind that they might still use an upstream provider who uses G.729 etc). Easiest option is to just choose aLaw or uLaw based on your country. -- Cheers, Matt Riddell Managing Director _______________________________________________ http://www.venturevoip.com/news.php (Daily Asterisk News) http://www.venturevoip.com/exchange.php (Full ITSP Solution) http://www.venturevoip.com/st.php (SmoothTorque Predictive Dialer)
Doesn't really matter unless you want to use zaptel lines on one end and VoIP lines on the other end, and want to avoid mismatch between your telco and your IP phones codecs. Transcoding between aLaw and uLaw in my experience can degrade voice quality. If you are using zaptel, and your telco supports aLaw, then use aLaw otherwise use uLaw. uLaw is North American standard and aLaw almost rest of the world. -- Zeeshan A Zakaria On 2010-03-23 3:48 PM, "Alejandro Cabrera Obed" <aco1967 at gmail.com> wrote: Dear all, I have an Asterisk SIP server in a LAN environment and I want your opinion in order to decide the use of an audio codec: What audio codec is better, G.711a or G.711u ??? Which suites to my LAN voip calls ??? Thank you !!! Alejandro -- _____________________________________________________________________ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- New to Asterisk? Join us for a live introductory webinar every Thurs: http://www.asterisk.org/hello asterisk-users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.digium.com/pipermail/asterisk-users/attachments/20100323/5c2703c1/attachment.htm
2010/3/23 Alejandro Cabrera Obed <aco1967 at gmail.com>:> Dear all, I have an Asterisk SIP server in a LAN environment and I want your > opinion in order to decide the use of an audio codec: > > What audio codec is better, G.711a or G.711u ??? Which suites to my LAN voip > calls ???That depends most on the codec used in your country IF you terminate calls to ISDN. In th USA (and some other countries) you would use G711u and in Europe etc. you would use G711a. Chris
fwiw, they both 'sound' the same, so if your question was specifically about not pest-terminated calls it still doesn't matter. :-) For that you could use something like g.722 provided your endpoints support it. In that case it really DOES make a big difference and the bandwidth is the same. -Karl ----- Original Message ----- From: "Alejandro Cabrera Obed" <aco1967 at gmail.com> To: "Asterisk Users Mailing List - Non-Commercial Discussion" <asterisk-users at lists.digium.com> Sent: Tuesday, March 23, 2010 2:41 PM Subject: [asterisk-users] G.711a or G.711u ???> Dear all, I have an Asterisk SIP server in a LAN environment and I want > your > opinion in order to decide the use of an audio codec: > > What audio codec is better, G.711a or G.711u ??? Which suites to my LAN > voip > calls ??? > > Thank you !!! > > Alejandro >--------------------------------------------------------------------------------> -- > _____________________________________________________________________ > -- Bandwidth and Colocation Provided by http://www.api-digital.com -- > New to Asterisk? Join us for a live introductory webinar every Thurs: > http://www.asterisk.org/hello > > asterisk-users mailing list > To UNSUBSCRIBE or update options visit: > http://lists.digium.com/mailman/listinfo/asterisk-users
On Tue, Mar 23, 2010 at 1:41 PM, Alejandro Cabrera Obed <aco1967 at gmail.com> wrote:> Dear all, I have an Asterisk SIP server in a LAN environment and I want your > opinion in order to decide the use of an audio codec: > > What audio codec is better, G.711a or G.711u ??? Which suites to my LAN voip > calls ???As others have stated, use whatever matches your country. In terms of the network, the traffic is exactly the same for both a-law and u-law. Both are 8khz sampled 8 bits per sample PCM (64kbps). The only difference between the two is the companding (http://en.wikipedia.org/wiki/Companding) algorithm that's used for the audio emphasis. To the network, the packets are 100% identical. Andrew> Thank you !!! > > Alejandro >