1. Downloading sources

You need ITU's sources for G.729 Annex A codec.

Grab it from ITU's site (search for "Zip (PDF)" link):
http://www.itu.int/rec/T-REC-G.729-199611-S!AnnA/en

You need g729anxaE folder which resides in:
T-REC-G.729-199611-S!AnnA!ZPF-E.zip.zip/software.zip/g729anxaE

2. Extracting sources.

Extract these directory into currect folder.

You should see:

<this dir>\
    g729anxaE\
        ACELP_CA.C
	BASIC_OP.C
	...
    Makefile
    README
    g729a.c
    g729a.h

3a. Builing library from ITU's sources

Now "make" will build libg729a.a for you

3b. Building natvie G.729 decoder (encoding is not supported)

"make native" will build lig729a.a from g729a_native.c
(out implementation of G.729 decoder).

4. Execute "make ffmpeg-cfg" followed by "make ffmpeg"

Above command will build ffmpeg with enabled ACT muxer/demuxer

6. Testing

Put any ACT file in this directory and rename it into "test.act"
Execute "make test" and you'll see decded test.wav file.

