As a part of the Media Overhaul project for Asterisk 1.10, changes have been made to Asterisk to increase the number of codecs it's capable of supporting, to handle codecs with custom formats, and to support audio sampling rates greater than 16kHz. This has resulted in several practical changes to Asterisk that will benefit its users.
Expanded Signed Linear Support
Versions of Asterisk prior to 1.10 supported 16-bit Signed Linear sampled at 8kHz and at 16kHz (versions 1.6.0-1.8). New to Asterisk 1.10 is support for a much wider range of sampling rates. Asterisk can resample between any of these sampling rates and can read/write raw 16-bit signed linear audio files from/to disk. The complete list of supported sampling rates and file format extensions is:
In this example, an input WAV file has been converted to RAW Signed Linear at a depth of 16-bits and at a rate of 32kHz. The resulting output.sln file is then renamed output.sln32 so that it can be processed correctly by Asterisk.
32kHz Speex Support
Asterisk versions prior to 1.8 supported 8kHz Speex. Asterisk 1.8 supports 8 and 16kHz Speex. Asterisk 1.10 now supports 8, 16, and 32kHz Speex. Use of the 32kHz Speex mode is, like the other modes, controlled in the respective channel driver's configuration file, e.g. chan_sip's sip.conf.