SIP SIMPLE Client SDK

= Echo cancellation =

<abbr title="Design*, depth=1">TOC</abbr>

SIP SIMPLE client is a Python software library that allows for easy development of Internet communications end-points based on SIP and related protocols for voice, rich presence, session based instant messaging (IM), file transfers and desktop sharing. Other media types can be easily added by using an extensible high-level API. SIP SIMPLE client uses [http://www.pjsip.org/pjmedia/docs/html/index.htm PJSIP media library] for audio processing (sound card abstraction, audio codec and acoustic echo cancellation).

For more information see http://sipsimpleclient.com

Background

The present implementation of the echo canceller from PJSIP media library is not performing to the desired level of quality. Practically, the speaker phone function of SIP SIMPLE client is not reliable and not performing satisfactory unless a headset is used.

[[Image(http://www.pjsip.org/images/media-flow.jpg)]]

Project goal

Develop or replace the existing AEC from Pjmedia library to provide the best user hand-free experience when using the software phone, that is the usage of the speakerphone function in small to medium rooms should not be audibly affected by the acoustic echo reflected by the walls.

The developed software will be released under an open source licence and distributed with SIP SIMPLE client library.

Resources

The following resources relates to open source AEC implementations:

• PJSIP media library http://pjsip.org, used by this project, AEC is implemented based on the Speex library, the code in pjsip/pjmedia/src/pjmedia/echo_speex.c
• Media flow - http://trac.pjsip.org/repos/wiki/media-flow
• Speex project http://speex.org, the echo canceller implements AEC based on the MDF algorithm, see speex/libspeex/mdf.c. A test client is available in speex/speexclient, this has been used for developing pjmedia equivalent
• http://www.andreadrian.de/intercom/ implements AEC based on NLMS algorithm (not tested yet)
• Kphone AEC implemented using above AEC http://www.andreadrian.de/echo_cancel/ (not tested)
• Graduation thesis about AEC http://innovexpo.itee.uq.edu.au/2003/exhibits/s365914/

Job description

Project based, result oriented, works must be performed from remote.