The present document specifies the AMR-WB backward compatible functions of the EVS codec.
The present document is a high level overview of the functionality with reference to the Codec Detailed Algorithmic
Description where the functionality is specified in detail.
The EVS coder provides enhanced AMR-WB backward compatible operation over all nine source bit rates from 6.6 kbit/s to 23,85 kbit/s, including AMR-WB backward compatible DTX operation. This backward compatible operation is referred to AMR-WB interoperable (AMR-WB IO).
Frames generated by an EVS AMR-WB IO encoder can be decoded by an AMR-WB decoder, without the need for transcoding. Correspondingly, frames generated by an AMR-WB encoder can be decoded by an EVS AMR-WB IO decoder, without the need for transcoding.
In addition to encoder and decoder enhancements, the AMR-WB backward compatible functions in the EVS coder provide the following extra functionalities compared to the AMR-WB coder specified in  to  and :
Support of input and output sampling frequencies other than 16 kHz (i.e. 8, 32, 48 kHz)
Inclusion of jitter buffer management for AMR-WB backward compatible functions
Switching between AMR-WB IO bit rates and primary EVS bit rates at any 20 ms speech frame boundary
The present document is mandatory for implementation in all network entities and UEs supporting the EVS codec.
In the case of discrepancy between the EVS codec backward compatible functions described in the present document and its ANSI-C code specification contained in  the procedure defined by  prevails. In the case of discrepancy between the procedure described in the present document and its ANSI-C code specification contained in  the procedure defined by  prevails. In the case of discrepancy between the procedure described in the present document and its ANSI-C code specification contained in  the procedure defined by  prevails.
full Table of Contents for TS 26.446 Word version: 16.0.0