Saturday, 22 December 2012

HD Voice - G.722 vs. AMR-WB vs Skype (SILK)

As the major telecom players (including Portuguese PT and Vodafone) and other carriers start to push HD voice in the mobile and fixed world, advocates are lining up behind their favorite bits of codes for delivering higher quality sound.  There are three different battles shaping up among the codec-heads.

Battle #1 - G.722 vs. AMR-WB (G722.2) – Wireline vs. wireless
G.722 is the granddaddy of wideband HD voice codec, codified as a standard back in 198xx by the ITU.  Designed in the days the era of single core CPUs running at Mhz speeds, it doesn’t use a lot of cycles and requires 64 kbit/s for a call – a lot of bandwidth back in the day,  but practically noise on any sort of broadband pipe these days.
IP phone guys have lined up behind G.722 because it’s easy to implement and there’s no licensing fees since the patents have expired. It’s the de facto standard for businesses and is also found in a lot of consumer gear.  Aastra, Allworx, AudioCodes,  Avaya, Cisco, Panasonic, Polycom, ShoreTel, Thomson, Siemens, Snom and practically every no-name on the planet have put it in their phones.

Designed by the cellular crowd and build on the GSM AMR narrowband standard, AMR-WB uses more CPU – and hence more power -- to deliver a HD voice session in 24 kbit/s.  Cellular guys want to squeeze every last Hz of RF bandwidth they can get, but heavier compression means shorter battery life.

Getting AMR-WB into wide circulation has been an uphill battle because it is a complicated piece of work with several different profiles to implement and test.  Further, the underlying technology has a bunch of patents on top of it. Patent holders include France Telecom and Ericsson – no big surprise the two are among the biggest advocates of the technology.

France Telecom and other carriers would like to see the HD voice world move to end-to-end AMR-WB because they then wouldn't have to worry about transcoding between cellular and broadband worlds.  VoiceAge, holder of the AMR-WB patent pool, has tweaked its royalty schedule to encourage incorporation of the codec into core network boxes and desktop IP phones.

Creeping up behind AMR-WB is the threat of over-the-top (OTT) softphone clients running on 4G networks.  Global IP Solutions (GIPS) has provided its proprietary iSAC codec to a number of softclients and D2 Technologies has added G.722 support to Android, so there's a lot of room for both G.722 and AMR-WB to proliferate.

Sampling comparing:

Bloggers note: Future of HD Voice in fixed IP communications is soon to be a reality although there are some challenges regarding the full support of AMR-WB, like support for deployed IP Phone models and special licensing (eg: 

Battle #2 - Skype's SILK vs. world
Skype stirred up a lot of people around this time last year when it announced its SILK superwideband codec.  The tech-geeks love the fact that SILK is a "superwideband" codec, that it's an adaptive bit-rate codec, adjusting quality based upon available CPU and network resources, and that it's available on a royalty-free basis.

At least one vendor - AudioCodes - has hinted it will roll SILK into its IP desktop handsets. However, some developers speaking off-the-record  have been less than enthusiastic with the process of working with Skype; more than one person indicated it's not clear who is calling the shots between Estonia, the UK, and California with a "non-linear" business evaluation process when it comes time for decisions.

Battle #3 - Large number of HD voice codecs vs. limited enthusiasm for supporting all
Free is one of the biggest myths on the planet.  While a codec may be royalty-free, each codec put into a software program or phone requires  space in the code/firmware, programming and integration support into a product, and another check-box on the testing laundry list before a product is finalized. 

One you plunk through G.722, AMR-WB, and SILK, plus legacy codecs for narrowband, each additional codec starts adding expense to the end-product for implementation and testing. At some point, you have to stop and get the phone out the door.

If you really want to muck things up, start throwing around phrases like "software indemnification" and start mumbling things about patents.  You're safe with code like G.722, where all the patents have expired and AMR-WB, since you pay royalties to use it.

Finally, carriers want to avoid transcoding between formats - especially between HD voice formats. Having to support a large number of codecs is not something to make a service provider of any size happy. 

Edited by the blogger

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