GSM-AMR Functions

This part of the chapter describes the Intel IPP functions that can be combined to construct a bit-exact implementation of the European Telecommunications Standards Institute (ETSI) Global System for Mobile Communications (GSM) Adaptive Multi-Rate (AMR) ETSI EN 301 704 GSM 06.90 version 7.5.0 Release 2001 speech codec, more commonly known as the GSM-AMR 06.90 codec. The primitives are primarily concerned with the well-defined, computationally expensive core operations that comprise the codec portion of the GSM-AMR system.

The GSM 06.90 AMR speech codec comprises an adaptive multi-rate algorithm that represents efficiently telephone-bandwidth digital speech using compressed data rates of 4.75, 5.15, 5.90, 6.70, 7.40, 7.95, 10.2, and 12.2 kilobits per second (kbps). The GSM-AMR system adaptively controls speech codec bit rates such that output quality is maximized for a given set of channel conditions.

These functions are used in the Intel IPP GSM/AMR Speech Encoder-Decoder sample downloadable from

The following table provides a list of these functions.

Intel IPP GSM-AMR Functions 
Function Base Name Operation
Basic Functions
Interpolate_GSMAMR Computes the weighted sum of two vectors.
FFTFwd_RToPerm_GSMAMR Computes the forward fast Fourier transform (FFT) of a real signal.
Linear Prediction Analysis Functions
AutoCorr_GSMAMR Estimates the autocorrelation sequence for a block of samples.
LevinsonDurbin_GSMAMR Calculates the LP coefficients using the Levinson-Durbin algorithm.
LPCToLSP_GSMAMR Converts LP coefficients to line spectrum pairs.
LSFToLSP_GSMAMR Converts Line Spectral Frequencies to LSP coefficients.
LSPToLPC_GSMAMR Converts LSPs to LP coefficients.
QuantLSPDEcode_GSMAMR Quantizes the LSP coefficient vector.
Adaptive Codebook Search Functions
OpenLoopPitchSearchNonDTX_GSMAMR Computes the OLP lag.
OpenLoopPitchSearchDTXVAD1_GSMAMR Extracts an OLP lag estimate (VAD 1 scheme is enabled).
OpenLoopPitchSearchDTXVAD2_GSMAMR Extracts an OLP lag estimate (VAD 2 scheme is enabled).
AdaptiveCodebookSearch_GSMAMR Performs the adaptive codebook search.
AdaptiveCodebookDecode_GSMAMR Decodes the adaptive codebook parameters.
ImpulseResponseTarget_GSMAMR Computes the impulse response and target signal required for the adaptive codebook search.
AdaptiveCodebookGain_GSMAMR Calculates the gain of the adaptive-codebook vector and the filtered codebook vector.
Fixed Codebook Search Functions
AlgebraicCodebookSearch_GSMAMR Searches the algebraic codebook.
FixedCodebookDecode_GSMAMR Decodes the fixed codebook vector.
Discontinuous Transmission functions
Preemphasize_GSMAMR Computes pre-emphasis of an input signal in VAD option 2.
VAD1_GSMAMR Implements the VAD functionality corresponding to VAD option 1.
VAD2_GSMAMR Implements the VAD functionality corresponding to VAD option 2.
EncDTXSID_GSMAMR Extracts parameters for the SID frame.
EncDTXHandler_GSMAMR Determines the SID flag of current frame.
EncDTXBuffer_GSMAMR, DecDTXBuffer_GSMAMR Buffer the LSP (or LSF) coefficients and previous log energy coefficients.
Post Processing Functions
PostFilter_GSMAMR Filters the synthesized speech.

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