view amrconv/if1_pack.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 4c4649a5fec3
children
line wrap: on
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/*
 * In this module we implement our function for packing AMR codec bits
 * from an array containing them in the codec's natural bit order
 * into the octet form of AMR IF1 and RFC 4867.
 */

#include <stdint.h>
#include "amr_defs.h"

extern const uint8_t amr_475_bit_order[95];
extern const uint8_t amr_515_bit_order[103];
extern const uint8_t amr_59_bit_order[118];
extern const uint8_t amr_67_bit_order[134];
extern const uint8_t amr_74_bit_order[148];
extern const uint8_t amr_795_bit_order[159];
extern const uint8_t amr_102_bit_order[204];
extern const uint8_t amr_122_bit_order[244];

static void
pack_bits(if1_bytes, codec_bits, nbits, table)
	uint8_t *if1_bytes, *codec_bits;
	unsigned nbits;
	const uint8_t *table;
{
	unsigned n, nb;

	for (n = 0; n < nbits; n++) {
		if (table)
			nb = table[n];
		else
			nb = n;
		msb_set_bit(if1_bytes, n, codec_bits[nb]);
	}
}

amr_if1_pack(if1_bytes, codec_bits, mode)
	uint8_t *if1_bytes, *codec_bits;
	unsigned mode;
{
	switch (mode) {
	case MR475:
		pack_bits(if1_bytes, codec_bits, AMR_NBITS_475,
				amr_475_bit_order);
		if1_bytes[11] &= 0xFE;
		return(0);
	case MR515:
		pack_bits(if1_bytes, codec_bits, AMR_NBITS_515,
				amr_515_bit_order);
		if1_bytes[12] &= 0xFE;
		return(0);
	case MR59:
		pack_bits(if1_bytes, codec_bits, AMR_NBITS_59,
				amr_59_bit_order);
		if1_bytes[14] &= 0xFC;
		return(0);
	case MR67:
		pack_bits(if1_bytes, codec_bits, AMR_NBITS_67,
				amr_67_bit_order);
		if1_bytes[16] &= 0xFC;
		return(0);
	case MR74:
		pack_bits(if1_bytes, codec_bits, AMR_NBITS_74,
				amr_74_bit_order);
		if1_bytes[18] &= 0xF0;
		return(0);
	case MR795:
		pack_bits(if1_bytes, codec_bits, AMR_NBITS_795,
				amr_795_bit_order);
		if1_bytes[19] &= 0xFE;
		return(0);
	case MR102:
		pack_bits(if1_bytes, codec_bits, AMR_NBITS_102,
				amr_102_bit_order);
		if1_bytes[25] &= 0xF0;
		return(0);
	case MR122:            
		pack_bits(if1_bytes, codec_bits, AMR_NBITS_122,
				amr_122_bit_order);
		if1_bytes[30] &= 0xF0;
		return(0);
	case MRDTX:
		pack_bits(if1_bytes, codec_bits, AMR_NBITS_SID,
				(const uint8_t *) 0);
		if1_bytes[4] &= 0xE0;
		return(0);
	default:
		return(-1);
	}
}