Add BDsound IMproved Audio Device (bdIMAD) integration

[riza]

BDSound IMproved Audio Device (bdIMAD) is a multiplatform audio interface
created to integrate in PJSIP library with no effort.

Features

• Echo cancellation (Full Duplex)
• Noise reduction
• Automatic Gain Control
• Audio Enhancement

Supported operating systems

• Windows
• Android
• MacOS X
• iOS
• Linux / Alsa

Supported platforms

• x86
• x64
• ARM Cortex-A8/A9/A15 with NEON

Using Pjsip with bdIMAD

• Request bdIMAD library from ​bdsound
• Enable bdIMAD by defining this on config_site.h

  #define PJMEDIA_AUDIO_DEV_HAS_BDIMAD	1
  

• Make sure you disable other sound device backends, by defining these on config_site.h

  #define PJMEDIA_AUDIO_DEV_HAS_PORTAUDIO 0
  #define PJMEDIA_AUDIO_DEV_HAS_WMME 0
  #define PJMEDIA_AUDIO_DEV_HAS_COREAUDIO 0 
  

• Since the bdIMAD library provide itself the echo cancellation and the latency management, is necessary to disable these features in the PJSIP librariy applications. For example in PJSUA sample application there is the need to provide the following commands:

  --ec-tail=0
  --no-vad
  --capture-lat=0
  --playback-lat=0
  

[riza]

In 4432:

Re #1636: add initial support for bdIMAD

[riza]

In 4501:

Re #1636: change include directive to relative path to simplify build config