This Recommendation describes a digital wideband coder algorithm that provides an audio bandwidth of 50 Hz to 7 kHz, operating at a bit rate of 24 kbit/s or 32 kbit/s. The digital input to the coder may be 14-, 15- or 16-bit 2’s complement format at a sample rate of 16 kHz (handled in the same way as in ITU-T Rec. G.722). The analogue and digital interface circuitry at the encoder input and decoder output should conform to the same specifications described in ITU-T Rec. G.722.
The algorithm is based on transform technology, using a Modulated Lapped Transform (MLT). It operates on 20-ms frames (320 samples) of audio. Because the transform window (basis function length) is 640 samples and a 50 per cent (320 samples) overlap is used between frames, the effective look-ahead buffer size is 20 ms. Hence the total algorithmic delay of 40 ms is the sum of the frame size plus look-ahead. All other delays are due to computational and network transmission delays.