FreeCalypso > hg > gsm-codec-lib
view libgsmefr/enc_main.c @ 242:f081a6850fb5
libgsmfrp: new refined implementation
The previous implementation exhibited the following defects,
which are now fixed:
1) The last received valid SID was cached forever for the purpose of
handling future invalid SIDs - we could have received some valid
SID ages ago, then lots of speech or NO_DATA, and if we then get
an invalid SID, we would resurrect the last valid SID from ancient
history - a bad design. In our new design, we handle invalid SID
based on the current state, much like BFI.
2) GSM 06.11 spec says clearly that after the second lost SID
(received BFI=1 && TAF=1 in CN state) we need to gradually decrease
the output level, rather than jump directly to emitting silence
frames - we previously failed to implement such logic.
3) Per GSM 06.12 section 5.2, Xmaxc should be the same in all 4 subframes
in a SID frame. What should we do if we receive an otherwise valid
SID frame with different Xmaxc? Our previous approach would
replicate this Xmaxc oddity in every subsequent generated CN frame,
which is rather bad. In our new design, the very first CN frame
(which can be seen as a transformation of the SID frame itself)
retains the original 4 distinct Xmaxc, but all subsequent CN frames
are based on the Xmaxc from the last subframe of the most recent SID.
author | Mychaela Falconia <falcon@freecalypso.org> |
---|---|
date | Tue, 09 May 2023 05:16:31 +0000 |
parents | 035424a6ca83 |
children |
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/* * This module contains our GSM EFR encoder main function, EFR_encode_params(), * that stands at the boundary between our public interface and the guts of * ETSI-based codec. */ #include "gsm_efr.h" #include "typedef.h" #include "namespace.h" #include "basic_op.h" #include "cnst.h" #include "codec.h" #include "sig_proc.h" #include "memops.h" #include "enc_state.h" #include "e_homing.h" #include "dtx.h" void EFR_encode_params(struct EFR_encoder_state *st, const int16_t *pcm_in, int16_t *params, int *sp_out, int *vad_out) { Word16 *new_speech = st->old_speech + L_TOTAL - L_FRAME; Word16 syn[L_FRAME]; Word16 reset_flag; Word16 i; /* Check whether this frame is an encoder homing frame */ reset_flag = encoder_homing_frame_test (pcm_in); for (i = 0; i < L_FRAME; i++) /* Delete the 3 LSBs (13-bit input) */ { new_speech[i] = pcm_in[i] & 0xfff8; } Pre_Process (st, new_speech, L_FRAME); /* filter + downscaling */ Coder_12k2 (st, params, syn); /* Find speech parameters */ if ((st->txdtx_ctrl & TX_SP_FLAG) == 0) { /* Write comfort noise parameters into the parameter frame. Use old parameters in case SID frame is not to be updated */ CN_encoding (st, params, st->txdtx_ctrl); } /* VAD and SP flag outputs */ if (vad_out) *vad_out = ((st->txdtx_ctrl & TX_VAD_FLAG) != 0); if (sp_out) *sp_out = ((st->txdtx_ctrl & TX_SP_FLAG) != 0); if (reset_flag != 0) { /* Bring the encoder, VAD and DTX to the home state */ EFR_encoder_reset(st, st->dtx_mode); } }