26.1923GPPAdaptive Multi-Rate - Wideband (AMR-WB) speech codecComfort noise aspectsRelease 17Speech codec speech processing functionsTS
For the purpose of this document, the following definitions apply.
Frame: Time interval of 20 ms corresponding to the time segmentation of the adaptive multi-rate wideband speech transcoder, also used as a short term for traffic frame.
SID frames: Special Comfort Noise frames. It may convey information on the acoustic background noise or inform the decoder that it should start generating background noise.
Speech frame: Traffic frame that cannot be classified as a SID frame.
VAD flag: Voice Activity Detection flag.
TX_TYPE: Classification of the transmitted traffic frame (defined in ).
RX_TYPE: Classification of the received traffic frame (defined in ).
Other definitions of terms used in this document can be found in  and . The overall operation of SCR is described in .
For the purpose of this document, the following symbols apply. Boldface symbols are used for vector variables.
Unquantized ISF vector
Quantized ISF vector
Unquantized ISF vector of frame m
Quantized ISF vector of frame m
Averaged ISF parameter vector
Logarithmic frame energy
Averaged logarithmic frame energy
ISF parameter prediction residual
Quantized ISF parameter prediction residual
For the purpose of this document , the following abbreviations apply.
AMR Adaptive Multi-Rate
AMR-WB Adaptive Multi-Rate Wideband
CN Comfort Noise
SCR Source Controlled Rate operation ( aka source discontinuous transmission )
UE User Equipment
SID SIlence Descriptor
LP Linear Prediction
ISP Immittance Spectral Pair
ISF Immittance Spectral Frequency
RSS Radio Subsystem
VAD Voice Activity Detector