DesignAEC

Version 13 (Adrian Georgescu, 08/27/2009 02:56 pm)

1 2 Adrian Georgescu
= Echo cancellation =
2 1 Adrian Georgescu
3 1 Adrian Georgescu
[[TOC(Design*, depth=1)]]
4 1 Adrian Georgescu
5 1 Adrian Georgescu
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).
6 1 Adrian Georgescu
7 1 Adrian Georgescu
For more information see http://sipsimpleclient.com
8 1 Adrian Georgescu
9 1 Adrian Georgescu
== Background ==
10 1 Adrian Georgescu
11 1 Adrian Georgescu
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.
12 1 Adrian Georgescu
13 1 Adrian Georgescu
[[Image(http://www.pjsip.org/images/media-flow.jpg)]]
14 1 Adrian Georgescu
15 1 Adrian Georgescu
16 1 Adrian Georgescu
== Project goal ==
17 1 Adrian Georgescu
18 13 Adrian Georgescu
Replace the existing AEC from Pjmedia library (what is displayed as echo.h in the above diagram) with a better solution to provide a high quality speakerphone user experience. The echo cancelation should perform comparable with any other proven VoIP commercial solution like Skype or iChat.
19 1 Adrian Georgescu
20 1 Adrian Georgescu
The developed software will be released under an open source licence and distributed with SIP SIMPLE client library.
21 1 Adrian Georgescu
22 11 Adrian Georgescu
The deliverable is C written program that can be applied to the pjsip  cvs trunk 1.0 with the '''patch''' command.
23 11 Adrian Georgescu
24 1 Adrian Georgescu
== Resources ==
25 1 Adrian Georgescu
26 7 Adrian Georgescu
General
27 1 Adrian Georgescu
28 7 Adrian Georgescu
 * Digital Signal Processing http://www.dsptutor.freeuk.com/
29 7 Adrian Georgescu
 * Graduation thesis about AEC  http://innovexpo.itee.uq.edu.au/2003/exhibits/s365914/
30 9 Adrian Georgescu
 * DSP concepts: http://www.bores.com/courses/intro/basics/index.htm
31 7 Adrian Georgescu
32 7 Adrian Georgescu
PJSIP media library
33 7 Adrian Georgescu
34 1 Adrian Georgescu
 * 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 
35 1 Adrian Georgescu
 * Media flow - http://trac.pjsip.org/repos/wiki/media-flow
36 12 Adrian Georgescu
 * PJSIP AEC API http://www.pjsip.org/pjmedia/docs/html/group__PJMEDIA__Echo__Cancel.htm
37 6 Adrian Georgescu
38 6 Adrian Georgescu
Speex AEC
39 6 Adrian Georgescu
40 1 Adrian Georgescu
 * 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
41 6 Adrian Georgescu
 * http://speex.org/docs/api/speex-api-reference/group__SpeexEchoState.html
42 1 Adrian Georgescu
43 1 Adrian Georgescu
Andree Adrian AEC
44 1 Adrian Georgescu
45 10 Adrian Georgescu
 * Draft AEC http://www.andreadrian.de/echo_cancel/draft-aec-03.txt
46 1 Adrian Georgescu
 * http://www.andreadrian.de/intercom/ implements AEC based on NLMS algorithm (not tested yet)
47 1 Adrian Georgescu
 * Kphone AEC implemented using above AEC http://www.andreadrian.de/echo_cancel/ (not tested)