SPEEX ECHO FOR THE BLACKFIN PROCESSORS

                
                
This library is based on rev 1.1.10 of the Speex source code found at 
www.speex.org.  It contains a fixed-point version of the Speex port.



                            WHAT IS SPEEX? 
           (Refer to http: //www.speex.org for more details)

Speex is based on CELP  and is designed to compress voice at bitrates 
ranging from 2 to 44 kbps. Some of Speex’s features include:

 * Narrowband (8 kHz), wideband (16 kHz), and ultra-wideband (32 kHz) 
   compression in the same bitstream.
 * Intensity stereo encoding.
 * Packet loss concealment.
 * Variable bitrate operation (VBR).
 * Voice Activity Detection (VAD).
 * Discontinuous Transmission (DTX).
 * In-progress fixed-point port.
 

 
                            BUILDING SPEEX

This library was build using VisualDSP++4.5 and tested on the BF561 EZ-KIT 
Lite platform using examples provided with the Blackfin SDK.



Software Setup
--------------

All the software was tested using VisualDSP++ 4.5 (June update)

This package includes all necessary source code file needed to build the
code as a library which then may be used in applications to en/decode
speech stream.

The library project and source code files are placed in the BlackfinSDK 
distribution folder for algortihms:
 "Program Files\Analog Devices\BlackfinSDK\Algorithms\OggSpeex-TremorLowMem"

The project file "LibSpeex533_FixedLowMem.dpj" is found inside the folder 
"ADSP-BF533".  This will build the these libraries:
  libspeex533_fixed_lowmem.dlb  - Release version
  libspeex533_fixed_lowmemd.dlb - Debug version
  
A binary version of each is included in the folder "Program Files\
Analog Devices\BlackfinSDK\Lib".  Examples that are included with the SDK
use them, so it is important to note that if you choose to use your version
of these libraries then you must move them to the appropriate folder 
location or change the example project options to find them elswhere 
where they are built.

Read comments in encdec.c to gain insight into the demo.  It contains two 
important user-configurable macros:

  ACTIVATE_STEREO - Define used to allow Speex to encode frame in stereo.
  ALWAYS_PASS_THROUGH - Define used to override Speex and pass the audio 
                        signal through in the audio callback.


                        
                                 REFERENCES

To learn about the Vorbis standard and the API for the Tremor libary, refer 
to http://www.xiph.org/ogg/vorbis/docs.html