Asterisk Software Add-ons

Find popular add-ons and more to extend the power of any Asterisk open source configuration.

G.729 Codec

Cut bandwidth requirements without sacrificing call quality. Standard G.711 calls take 64kbit/s per call. The G.729 codec compresses the payload to 8kbit/s, giving you up to eight (8) times the capacity on the same connection. Ideal for use in limited bandwidth scenarios (ADSL connections, international VoIP service, satellite connections, etc.).

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Up To 140 Calls On A Single T1

A practical example is the number of calls that may be carried across a standard 1.5 megabit/s T1 link. When using uncompressed G.711 audio, one can expect 18 concurrent calls across a T1. When using G.729 compression and Digium's IAX2 Trunking, instead of SIP, signaling protocol, one can expect about 140 concurrent calls across the same link.

Digium's implementation of the G.729 codec allows Asterisk software to convert audio between G.729 and any other supported codec. Many IP telephones and VoIP gateways include support for G.729. With the Digium G.729 Codec for Asterisk, those devices can now exchange calls with Asterisk directly at a fraction of the bandwidth of standard G.711.

Without the capability to transcode G.729, Asterisk software can only pass-through G.729 data between endpoints. This means that basic station to station calling can be made to work, but the advanced PBX features of Asterisk such as Call Conferences, DTMF digit collection, Call Recording and more will not work without Digium's licensed G.729 Codec.

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Digium's software G.729 codec utilizes the power of the host system's CPU to perform media transformations. Therefore, the transcoding capacity, in terms of simultaneous channels/transcodes, is determined by the performance of the host server. Digium's internal testing indicates that 60 concurrent G.729 calls/transcodes require a system equivalent to a dual Intel Xeon at 1.8GHz. Further testing indicates that 80 concurrent G.729 calls/transcodes require something equivalent to a dual Intel Xeon at 2.8GHz.

Multiple versions of G.729 are defined according to industry standards. Asterisk and Digium's G.729 implementation support G.729 Annex A (a.k.a. G.729a).

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Digium's G.729 Codec for Asterisk is licensed on a per-channel basis. A channel is defined as a single connection from an endpoint to an Asterisk application, or a bi-directional call between two endpoints attached to Asterisk. Customers may use the licensed G.729 Codec in conjunction with Asterisk and any combination of Digium telephony interface boards.

Supported Configurations

The G.729 codec is supported by the Digium technical support organization for use on Linux x86 and x86_64 environments.

Hardware Alternatives

For high-density applications, users should consider Digium's TC400B. The TC400B is a PCI card that offloads the transcoding burden from the host CPU. As a hardware product with dedicated digital signal processors, the Digium TC400B can process up to 120 G.729a streams and also supports the G.723.1 codec. Unlike Digium's software G.729 Codec, the TC400B does not require any per-channel licensing fees.

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Digium Voice Compression Telephony Card

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