FreeCalypso > hg > gsm-codec-lib
view libgsmefr/bfi_nodata.c @ 183:452c1d5a6268
libgsmefr BFI w/o data: emit zero output after decoder reset
In real-life usage, each EFR decoder session will most likely begin
with lots of BFI frames before the first real frame arrives. However,
because the spec-defined home state of the decoder is speech rather
than CN, our regular logic for BFI w/o data would have to feed
pseudorandom noise to the decoder (in the "fixed codebook excitation
pulses" part), which is silly to do at the beginning of the decoder
session right out of reset. Therefore, let's check reset_flag_old,
and if we are still in the reset state, simply emit zero output.
author | Mychaela Falconia <falcon@freecalypso.org> |
---|---|
date | Tue, 03 Jan 2023 00:12:18 +0000 |
parents | eefef9f6d533 |
children |
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/* * In the expected usage mode of our libgsmefr decoder as part of "soft TRAU" * uplink implementation, there will be times when the radio subsystem tells * us that a frame has been lost, but we don't have any errored bits to feed * to the decoder as ETSI canon calls for. Specifically, the canonical EFR * decoder will use the "fixed codebook excitation pulses" part of errored * frames when a BFI comes in after speech, although not when BFI comes in * after SID. Our solution in EFR_decode_bfi_nodata(): we look in the * decoder state to see if we are in speech mode, and if we are, we fill * the needed parameters with a PRNG. */ #include <string.h> #include "gsm_efr.h" #include "typedef.h" #include "namespace.h" #include "cnst.h" #include "dtx.h" #include "dec_state.h" static void random_1035(Word32 *lfsr, Word16 *param_1035) { Word16 *p = param_1035; Word16 i; /* 5 params of bit width 4 */ for (i = 0; i < 5; i++) *p++ = pseudonoise(lfsr, 4); /* another 5 params of bit width 3 */ for (i = 0; i < 5; i++) *p++ = pseudonoise(lfsr, 3); } static void random_bad_frame(struct EFR_decoder_state *st, Word16 *params) { Word32 *lfsr = &st->L_pn_seed_nodata; random_1035(lfsr, params + 7); random_1035(lfsr, params + 20); random_1035(lfsr, params + 33); random_1035(lfsr, params + 46); } void EFR_decode_bfi_nodata(struct EFR_decoder_state *st, int taf, int16_t *pcm_out) { int16_t params[EFR_NUM_PARAMS]; if (st->reset_flag_old) { memset(pcm_out, 0, sizeof(int16_t) * L_FRAME); return; } memset(params, 0, sizeof(int16_t) * EFR_NUM_PARAMS); if (st->rxdtx_ctrl & RX_SP_FLAG) random_bad_frame(st, params); EFR_decode_params(st, params, 1, 0, taf, pcm_out); }