G.722.1 describes a digital wideband coder algorithm that provides an audio bandwidth of 50 Hz to 7 kHz, operating at a bit rate of 24 kbps or 32 kbps. G.722.1 is useful for hands-free operation in systems with low frame loss
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.
The digital input to the coder may be 14, 15 or 16 bit 2's complement format at a sample rate of 16 kHz. It is handled in the same way as outlined in ITU Recommendation G.722. The analogue and digital interface circuitry at the encoder input and decoder output conforms to the same specifications described as G.722.