G.729.1

G.729.1 is an 8- embedded speech and audio codec providing bitstream interoperability with G.729, G.729 Annex A and G.729 Annex B. Its official name is G.729-based embedded variable bit rate codec: An 8- scalable wideband coder bitstream interoperable with G.729. It was introduced in 2006.
This codec has been designed to provide better quality and more flexibility than the existing ITU-T G.729 speech coding standard.
G.729.1 is scalable in bit rate, acoustic bandwidth and complexity.
In addition it offers various encoder and decoder modes, including the support of both 8 and input/output sampling frequency, compatibility with G.729B, and reduced algorithmic delay.
The bitstream of G.729.1 is structured into 12 hierarchical layers.
The first layer at follows the G.729 format.
The second layer is a narrowband enhancement layer. The third layer is a bandwidth extension layer. Further layers are wideband enhancement layers.
The G.729.1 output bandwidth is 5- at 8 and, and 50– from 14 to. G.729.1 is also known as G.729 Annex J and G.729EV where EV stands for Embedded Variable.
The G.729.1 algorithm is based on a three-stage coding structure: embedded code-excited [linear prediction] coding of the lower band, parametric coding of the higher band by Time-Domain Bandwidth Extension, and enhancement of the full band by a predictive transform coding technique referred to as time-domain aliasing cancellation or modified discrete cosine transform coding.