AMR Wideband Plus Functions

The Intel IPP functions described in this section if properly combined can be used to construct the Extended Adaptive Multi-Rate Wideband (AMR WB+) Speech Codec compliant to 3rd Generation Partnership Project (3GPP) specification TS 26.273: “ANSI-C code for fixed-point Extended AMR Wideband (AMRWB+) Speech Codec". The description of AMRWB+ codec may be found in 3GPP Technical Specification 26.290: “Extended AMR Wideband Speech Codec; Transcoding functions" [AMRWB+].

The primitives are primarily designed to implement the well-defined, computationally expensive core operations that comprise the codec portion of the AMRWB+ system. The AMRWB+ codec comprises an extended adaptive multi-rate algorithm, intended for encoding 16-bit uniform PCM at the sampling rate of 16, 24, 32 and 48 KHz. The AMRWB+ codec supports AMRWB compatible modes: 6.60, 8.85, 12.65, 14.25, 15.85, 18.25, 19.85, 23.05 or 23.85 kbps for 16 KHz PCM, four special extension stereo modes: 13.6, 18.0, 24.0 kbps and 24.0 kbps for fixed internal sampling frequency only (25600 Hz) and input PCM 16 or 24 kHz with 20ms frame length. Besides, for thirteen internal sampling frequencies: 12800, 14400, 16000, 17067, 19200, 21333, 24000, 25600, 28800, 32000, 34133, 36000, 38400 and 16, 24, 32 and 48 KHz PCM audio AMRWB+ supports 24 extended bitrates, resulted for fixed internal frequency 25600 Hz in eight mono: 10.4, 12.0, 13.6, 15.2, 16.8, 19.2, 20.8 and 24 kbps, and sixteen stereo bitrates: from 2.0 to 8.0 kbps with step of 0.4 kbps. For each internal sampling frequency ISF supported by AMRWB+ codec the correspondent 24 bitrates can be calculated by multiplication to ISF/25600, that is 1/2, 9/16, 5/8, 2/3, 3/4, 5/6, 15/16, 1, 9/8, 5/4, 4/3, 45/32 and 3/2 respectively. For example, for ISF=12800 with multiplier=1/2, the following bitrates are supported: eight mono 5.2, 6.0, 6.8, 7.6, 9.6, 10.4 and 12 kbps, and sixteen stereo bitrates: from 1.0 to 4.0 with step 0.2 kbps.

The following table lists the Intel IPP AMR WB Plus functions .

Intel IPP AMR WB Plus Functions
Function Base Name	Operation
SNR_AMRWBE	Computes the signal-to-noise ratio
OpenLoopPitchSearch_AMRWBE	Extracts an OLP lag estimate from the weighted input speech
LPCToISP_AMRWBE	Performs LP to ISP coefficients conversion
SynthesisFilter_AMRWBE	Reconstructs the speech signal from LP coefficients and residuals
Deemphasize_AMRWBE	Performs de-emphasis filtering
FIRGenMidBand_AMRWBE	Computes a shape-constrained FIR filter using the covariance method
PostFilterLowBand_AMRWBE	Post-processes the low-band decoded signal
FFTFwd_RToPerm_AMRWBE	Computes the forward fast Fourier transform (FFT) of a real signal
FFTInv_PermToR_AMRWBE	Computes the inverse fast Fourier transform (FFT) of a real signal
AdaptiveCodebookSearch_AMRWBE	Performs the adaptive codebook search
AdaptiveCodebookDecode_AMRWBE	Decodes the adaptive codebook vector
Downsample_AMRWBE	Performs signal downsampling
Upsample_AMRWBE	Performs signal upsampling
BandSplit_AMRWBE	Gets the vector of energy levels form VAD memory
BandJoin_AMRWBE	Joins the low and high frequency signals
BandSplitDownsample_AMRWBE	Decimates input signal and splits it into high and low frequency components
BandJoinUpsample_AMRWBE	Joins high and low frequency signals and upsamples the result
ResamplePolyphase_AMRWBE	Oversamples or downsamples the input signal to or from the upper frequency (44.1/48 khz)
ISFQuantDecode_AMRWBE	Decodes quantized ISF of HF-band signal.
ISFQuantDecodeHighBand_AMRWBE	Performs ISF quantization of HF-band encoded signal
ISFQuantHighBand_AMRWBE	Performs ISF quantization of HF-band encoded signal
GainQuant_AMRWBE	Quantizes the adaptive codebook gains
QuantTCX_AMRWBE	Quantizes the pre-shaped spectrum in TCX mode
GainQuantTCX_AMRWBE	Performs the gain optimization and quantization
GainDecodeTCX_AMRWBE	Decodes the global TCX gain
EncodeMux_AMRWBE	Encodes and multiplexes subvectors into several packets
DecodeDemux_AMRWBE	Demultiplexes and decodes subvectors from several packets