FreeCalypso > hg > gsm-codec-lib
view libgsmfr2/table.c @ 581:e2d5cad04cbf
libgsmhr1 RxFE: store CN R0+LPC separately from speech
In the original GSM 06.06 code the ECU for speech mode is entirely
separate from the CN generator, maintaining separate state. (The
main intertie between them is the speech vs CN state variable,
distinguishing between speech and CN BFIs, in addition to the
CN-specific function of distinguishing between initial and update
SIDs.)
In the present RxFE implementation I initially thought that we could
use the same saved_frame buffer for both ECU and CN, overwriting
just the first 4 params (R0 and LPC) when a valid SID comes in.
However, I now realize it was a bad idea: the original code has a
corner case (long sequence of speech-mode BFIs to put the ECU in
state 6, then SID and CN-mode BFIs, then a good speech frame) that
would be broken by that buffer reuse approach. We could eliminate
this corner case by resetting the ECU state when passing through
a CN insertion period, but doing so would needlessly increase
the behavioral diffs between GSM 06.06 and our version.
Solution: use a separate CN-specific buffer for CN R0+LPC parameters,
and match the behavior of GSM 06.06 code in this regard.
| author | Mychaela Falconia <falcon@freecalypso.org> |
|---|---|
| date | Thu, 13 Feb 2025 10:02:45 +0000 |
| parents | 19db59c9dc07 |
| children |
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/* * This C source file has been adapted from TU-Berlin libgsm source, * original notice follows: * * Copyright 1992 by Jutta Degener and Carsten Bormann, Technische * Universitaet Berlin. See the accompanying file "COPYRIGHT" for * details. THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE. */ #include <stdint.h> #include "tw_gsmfr.h" #include "typedef.h" #include "ed_state.h" #include "ed_internal.h" /* 4.4 TABLES USED IN THE FIXED POINT IMPLEMENTATION OF THE RPE-LTP * CODER AND DECODER * * (Most of them inlined, so watch out.) */ /* Table 4.1 Quantization of the Log.-Area Ratios */ /* i 1 2 3 4 5 6 7 8 */ word gsm_A[8] = {20480, 20480, 20480, 20480, 13964, 15360, 8534, 9036}; word gsm_B[8] = { 0, 0, 2048, -2560, 94, -1792, -341, -1144}; word gsm_MIC[8] = { -32, -32, -16, -16, -8, -8, -4, -4 }; word gsm_MAC[8] = { 31, 31, 15, 15, 7, 7, 3, 3 }; /* Table 4.2 Tabulation of 1/A[1..8] */ word gsm_INVA[8]={ 13107, 13107, 13107, 13107, 19223, 17476, 31454, 29708 }; /* Table 4.3a Decision level of the LTP gain quantizer */ /* bc 0 1 2 3 */ word gsm_DLB[4] = { 6554, 16384, 26214, 32767 }; /* Table 4.3b Quantization levels of the LTP gain quantizer */ /* bc 0 1 2 3 */ word gsm_QLB[4] = { 3277, 11469, 21299, 32767 }; /* Table 4.4 Coefficients of the weighting filter */ /* i 0 1 2 3 4 5 6 7 8 9 10 */ word gsm_H[11] = {-134, -374, 0, 2054, 5741, 8192, 5741, 2054, 0, -374, -134 }; /* Table 4.5 Normalized inverse mantissa used to compute xM/xmax */ /* i 0 1 2 3 4 5 6 7 */ word gsm_NRFAC[8] = { 29128, 26215, 23832, 21846, 20165, 18725, 17476, 16384 }; /* Table 4.6 Normalized direct mantissa used to compute xM/xmax */ /* i 0 1 2 3 4 5 6 7 */ word gsm_FAC[8] = { 18431, 20479, 22527, 24575, 26623, 28671, 30719, 32767 };