[Iaxclient-devel] New features in iaxclient library.

[Steve K. <st...@st...>]

I forget what I've announced to the list, and what I haven't.

The main new features added to the library recently are:

A bunch of signal processing stuff from speex:

1) A denoising filter:  This is a very effective filter which reduces 
background noise.
2) New AGC: This AGC implementation from speex seems to work much better 
than the compander implementation I've been using previously.
3) A new "automatic" silence detection based on speex' VAD.  If you set 
the silence threshold to a positive number, you now get speex' VAD, 
instead of my hacky noise-threshold code.
4) Bias removal:  Removes bias from input signals.  This makes other DSP 
functions work correctly, including the level metering, which was often 
incorrect when bias was present.


5) echo cancellation:  I modularized the echo cancellation a bit.  You 
can include one of speex' echo cancellation, MEC2/3, or Steve 
underwood's echo canceller via compile-time options.  Speex' echo 
canceller is included by default.

Echo cancellation via speex is still "experimental" in nature.  In 
particular, it is not very effective when you're also using AGC, because 
residual echo is boosted back up to full strength.  When you're not 
using AGC, it is somewhat effective in my limited testing.

Each of the denoiser, AGC, and echo cancellation can be enabled/disabled 
by calls to the library through this API:

#define IAXC_FILTER_DENOISE     (1<<0)
#define IAXC_FILTER_AGC         (1<<1)
#define IAXC_FILTER_ECHO        (1<<2)
int iaxc_get_filters(void);
void iaxc_set_filters(int filters);


Another thing that was added was automatic call disconnection when the 
remote endpoint is no longer reachable.  This happens if the remote 
endpoint crashes, for example.  Previously, there would be no indication 
of this to users.  Now, the call will be disconnected.

There have also been a bunch of bugfixes recently.  One important one 
was for the virtualMono implementation, where when there were no 
incoming frames (or you were just playing a sound), some garbage would 
be sent along to the sound card.  This made sound playback without an 
active call work improperly.

Also of note, I just found out that there's another libiaxclient library 
user out there:  DIAX is based on iaxclient.   I think that the author 
is presenly trying to migrate to a newer version of our library, with 
IAX2 support.

-SteveK