Performs the gain optimization and quantization.
Syntax
IppStatus ippsGainQuantTCX_AMRWBE_16s(const Ipp16s* pSrcSignal, Ipp16s srcScale, const Ipp16s* pSrcQuantSignal, int len, Ipp32s quantFlag, Ipp32s* pGain, Ipp16s* pQuantIdx);
Parameters
pSrcSignal |
Pointer to the original weighted signal. |
srcScale |
Format of input signal. |
pSrcQuantSignal |
Pointer to the quantized weighted signal. |
len |
Length of the source vector. |
quantFlag |
If equals to 0, then the function computes and returns the optimal gain only, else computes and returns the quantized gain and quantization index. |
pGain |
Pointer to the output quantized or optimal gain. |
pQuantIdx |
Pointer to the output index of quantization. |
Description
The function ippsGainQuantTCX_AMRWBE is declared in ippsc.h file. This function performs the gain optimization and quantization to maximize the correlation between the original weighted signal pSrcSignal(x) and the quantized weighted signal pSrcQuantSignal (x' ). The optimal gain g* between x and x' is computed in accordance with the following formula:
The gain g* is quantized on the logarithmic scale to a 7-bit index in the following way:
- compute the energy of the quantized
weighted signal
;
- compute the RMS value rms = 4(E/len)1/2;
- compute the index index = 28log(rms g*) + 0.5;
- if index < 0, then set index = 0; if index > 127, then set index = 127;
- and the quantized gain g'* = 10index/28rms
See also 3GPP TS 26.290: “Extended AMR Wideband Speech Codec; Transcoding functions", clause 5.3.5.10 [AMRWB+].
Return Values
ippStsNoErr |
Indicates no error. |
ippStsNullPtrErr |
Indicates an error when one of the specified pointer is NULL. |
ippStsSizeErr |
Indicates an error when len is less than or equal to zero. |