The EVS coder (TS 26.441
) provides enhanced quality for speech and audio communications compared to AMR-WB and 3GPP has standardized both a fixed-point version (TS 26.442
) and a floating-point version (TS 26.443
). Currently in TS 26.444
(Codec for Enhanced Voice Services (EVS); Test sequences) the conformance of the EVS coder implementation is achieved by checking the bit-exactness of output test vectors with the reference test vectors for both encoder and decoder, for both the fixed-point and floating-point implementations.
However, the bit-exact criteria defined in TS 26.444
is of very limited use for the floating-point implementation in TS 26.443
, as the output values will change slightly without affecting the speech/audio quality - depending on the compiler, compile options, OS and platform - and therefore failing the bit-exactness test. This has the effect that the EVS floating-point code cannot generally be used for 3GPP voice services as the test vectors have been generated using Microsoft Visual Studio version 10 which is unlikely to match the target platform.
The product and application space using voice services is changing, resulting in different architectures using a variety of different types of core processing units. Being able to use either fixed-point or floating-point embedded implementation based on architectural capabilities would allow a wider and faster proliferation of EVS, thereby benefiting end user experience. In addition, it would provide more flexibility in architectural implementations regarding factors such as power and cost.
This report investigates possible tools and criteria to develop non bit-exact conformance for the floating-point code in TS 26.443
, ensuring that high quality floating-point implementations preserve the quality of EVS.