How can I convert GSM sound files to G.729 format? I've used Sox in the past for transcoding sound files, but have not been able to find a way to transcode to G.729. Using Sox, I have found a way to convert GSM to WAV.
A free and easy way to convert proper sound files to G.729 is adding appropriate free G.729 codec binary to Asterisk and use 'convert' module.
You can follow these steps: