I am working on my VoIP project. I am having real difficulties on design my speech vocoders. It should fit into a low cost DSP from Analog Devices or TI that will receive data from a 16 bit A/D – D/A and store it in a flash using some sort of audio compression, (The audio is speech only) then each sample needs to be tagged for later retrieval, meaning it is not A FIFO, we should be able to retrieve any and all audio files stored in flash whenever and also be able to store a small amount of data.
I think a G722 vocoder is a good choice for your case. You can go to this Gao research company to get more infomation. the URL is http://www.gaoresearch.com/
In our project, we use their G729 Vocoder. It’s very good.