As Next Generation Networks (NGN) transition to fully IP-based architectures, the need for audio transcoding has sky-rocketed. The number of audio codecs continues to increase, and with the increasing adoption of wideband audio, the need for high-capacity audio transcoding is becoming critical.
Various network elements require audio transcoding. In an IMS architecture, the Media Resource Function Processor (MRFP) is responsible for all media-related functions, including transcoding to maintain inter-operability. In other network settings, the IMS-MGW may perform IP audio transcoding as well as convert between the PSTN and NGN.
Wide Range of Codecs
Octasic solutions provide a complete out-of-the-box software package that delivers a complete audio transcoding solution. Octasic actively participates in standards bodies for codec definition, and therefore is on the forefront, delivering the latest Internet and Wireless codecs.
These codecs include:
|Wireline||G.711, G.711.1, G.723.1, G.729AB, G.729.1, G.726|
|Wireless||AMR, AMR-WB (G.722.2), Enhanced full rate (GSM-EFR), Full Rate (GSM-FR), Half Rate (GSM-HR)
EVRC*, EVRC-B*, EVRC-C*
|Internet||iLBC, Speex, T.38 fax relay|
|Enterprise||G.722, G.722.1, RT-Audio*|
* Roadmap items, contact Octasic for release date.
Wideband audio is becoming the new norm. Codecs such as Wideband AMR (G.722.2) are already being deployed by certain mobile operators. G.722 and G.722.1 have become commonplace in many enterprise settings, since these networks were often closed allowing for interoperability between compatible devices.
Converting between wideband codecs requires a large amount of processing power, as well as maintaining the full audio spectrum in order to maintain fidelity.
Octasic delivers the highest capacity solutions for audio transcoding in the IP domain. Octasic’s Vocallo MGW product can transcode over 400 channels from G.711 to G.729AB on a single DSP, while consuming less that 2 watts of power!
One of the most important elements of voice quality in audio transcoding is the latency incurred. Octasic uses a sophisticated scheduling algorithm that dispatches packet transcode tasks across multi-core hardware. This reduces processing latency to sub-5 milliseconds when the system is operating at maximum capacity.
Packet Size Conversion
In addition to converting between various codec formats, it is often necessary to convert between packet sizes. This can be for a same codec, or between two codecs. Converting between G.711 (10 ms) and G.711 (20 ms) is a common occurrence. This also applies to different packet sizes, such as G.723 (30 ms) and G.711 (20 ms).
The solution must be able to accommodate any packet size supported for each codec. Some codecs require packet sizes in excess of 50 – 60 ms for long latency links like satellite.
Finally, audio transcoding requires the transcoding or mediation between more than just voice payload formats. The same gateway must also convert the following things: RTCP reports, RFC2833/4733 DTMF/Tone relay packets, T.38 fax, modem connections, and IPv4 & IPv6 headers.