Super-frame based source controlled variable rate coding using approximated trellis diagram

This paper proposes a variable rate control method for speech/audio coding; the assumption is that all super-frames passed during the connection have a constant bit rate. The method optimizes the bit rate allocated to each frame in a super-frame by using an approximated trellis diagram that represents a transition of an averaged bit rate. The approximation is to ignore the difference of memories in the encoder among the different modes. Simulations that implemented the method on AMR Wideband (AMR-WB) show that, allowing for a 100 ms additional algorithmic delay, the method achieves a maximum of about 4.3 dB improvement in the perceptual weighted Signal-to-Noise ratio, compared to constant rate coding.