Ongoing research projects

Choice of the support

The computational complexity of the Celp coders asks powerful workstations or specialised board for run in real time. We envisage two ways:
  • For the complex coders, we make the porting on a DSP board. (Digital Signal Processor: TMS320C30, AD2100, ...).
  • For the others coders, we use PC or Sun station after simplifications of few coder's block if necessary. This is the example for the Low Delay Celp at 16 kbit/s (ITU G.728) which runs in real time on a Pentium 90MHz.
For the DSP Board, we have chosen the new TMS320C32 Digital Signal Processor from Texas Intruments. If you want more information about this floating-point processor, you may consult :

TMS320C3x Floating-point DSPs


All the coders that we develop are based on a Coding ToolKit (CTK).
This tool-kit includes the next functions:

  • Speech processing functions.
  • Filters functions.
  • Statistic functions.
  • Specialized functions as codebook search for the CELP, pitch determination, ...
  • Special training functions of the codebooks (Stochastic codebooks, overlapped codebooks, ...)
  • ...

This toolkit is written in C++ and follows the structure presented in

"Anals of telecommunications: The OOBP programming paradigm: a VHDL-like object oriented approach toward developing efficient DSP software libraries" (Thierry Dutoit, Vincent Fontaine).

Coders adapted to the Coding ToolKit

  • The LD_CELP at 16 kbit/s.
  • The LD_CELP at 8 kbit/s.

  • The CELP at 8 kbit/s.
  • The CELP at 4.3 kbit/s.

  • See Available products

New coders

The next coders that will be developed is:
  • The VSELP at 8 kb/s.

Last updated December 17, 1999, send comments to