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New Wideband Codecs In Freeswitch

Over the past couple of days the Freeswitch developers have announced support for several newer wideband capable codecs. Thier first announcement was support for the Polycom Siren(tm) 7 and Siren(tm) 14, aka G.722.1 and G.722.1 Annex C. These provide sample rates of 16khz and 32 khz respectively. They also provide for modest bitrates, allowing wideband calling over bandwidth constrained connections.

One of their earlier uses was in the Soundstation VTX 1000 product. This was described by David Frankel of ZipDX on Novembers VUC call on wideband telephony. It actually establishes a point to point connection between two VTX1000 systems using analog v.90 modems. The VoIP call is then passed over the 56kbps modem connection. It’s a little byzantine to be sure, but it does provide point-to-point wideband calling over the PSTN.

They go on to add support for a new open source codec called “CELT” that they claim provides 48 khz sampling and requires just 48 kbps of bandwidth. CELT is part of the project and claims very low latency, which is great for voice.

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