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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 7960744ba19c
children
line wrap: on
line source

/*
 * This code (lifted from OsmocomBB) facilitates the conversion of 33-byte
 * GSM 06.10 encoded speech frames between the bit order at the 06.10 interface
 * in the de facto standard libgsm implementation and the bit order at the
 * 05.03 channel encoder interface, as realized in TI's Calypso DSP.
 */

#include <sys/types.h>
#include <string.h>
#include <strings.h>

/* GSM FR - subjective importance bit ordering */
	/* This array encodes GSM 05.03 Table 2.
	 * It's also GSM 06.10 Table A.2.1a
	 *
	 * It converts between serial parameter output by the encoder and the
	 * order needed before channel encoding.
	 */
const u_short gsm0610_bitorder[260] = {
	0,	/* LARc0:5 */
	47,	/* Xmaxc0:5 */
	103,	/* Xmaxc1:5 */
	159,	/* Xmaxc2:5 */
	215,	/* Xmaxc3:5 */
	1,	/* LARc0:4 */
	6,	/* LARc1:5 */
	12,	/* LARc2:4 */
	2,	/* LARc0:3 */
	7,	/* LARc1:4 */
	13,	/* LARc2:3 */
	17,	/* LARc3:4 */
	36,	/* Nc0:6 */
	92,	/* Nc1:6 */
	148,	/* Nc2:6 */
	204,	/* Nc3:6 */
	48,	/* Xmaxc0:4 */
	104,	/* Xmaxc1:4 */
	160,	/* Xmaxc2:4 */
	216,	/* Xmaxc3:4 */
	8,	/* LARc1:3 */
	22,	/* LARc4:3 */
	26,	/* LARc5:3 */
	37,	/* Nc0:5 */
	93,	/* Nc1:5 */
	149,	/* Nc2:5 */
	205,	/* Nc3:5 */
	38,	/* Nc0:4 */
	94,	/* Nc1:4 */
	150,	/* Nc2:4 */
	206,	/* Nc3:4 */
	39,	/* Nc0:3 */
	95,	/* Nc1:3 */
	151,	/* Nc2:3 */
	207,	/* Nc3:3 */
	40,	/* Nc0:2 */
	96,	/* Nc1:2 */
	152,	/* Nc2:2 */
	208,	/* Nc3:2 */
	49,	/* Xmaxc0:3 */
	105,	/* Xmaxc1:3 */
	161,	/* Xmaxc2:3 */
	217,	/* Xmaxc3:3 */
	3,	/* LARc0:2 */
	18,	/* LARc3:3 */
	30,	/* LARc6:2 */
	41,	/* Nc0:1 */
	97,	/* Nc1:1 */
	153,	/* Nc2:1 */
	209,	/* Nc3:1 */
	23,	/* LARc4:2 */
	27,	/* LARc5:2 */
	43,	/* bc0:1 */
	99,	/* bc1:1 */
	155,	/* bc2:1 */
	211,	/* bc3:1 */
	42,	/* Nc0:0 */
	98,	/* Nc1:0 */
	154,	/* Nc2:0 */
	210,	/* Nc3:0 */
	45,	/* Mc0:1 */
	101,	/* Mc1:1 */
	157,	/* Mc2:1 */
	213,	/* Mc3:1 */
	4,	/* LARc0:1 */
	9,	/* LARc1:2 */
	14,	/* LARc2:2 */
	33,	/* LARc7:2 */
	19,	/* LARc3:2 */
	24,	/* LARc4:1 */
	31,	/* LARc6:1 */
	44,	/* bc0:0 */
	100,	/* bc1:0 */
	156,	/* bc2:0 */
	212,	/* bc3:0 */
	50,	/* Xmaxc0:2 */
	106,	/* Xmaxc1:2 */
	162,	/* Xmaxc2:2 */
	218,	/* Xmaxc3:2 */
	53,	/* xmc0_0:2 */
	56,	/* xmc0_1:2 */
	59,	/* xmc0_2:2 */
	62,	/* xmc0_3:2 */
	65,	/* xmc0_4:2 */
	68,	/* xmc0_5:2 */
	71,	/* xmc0_6:2 */
	74,	/* xmc0_7:2 */
	77,	/* xmc0_8:2 */
	80,	/* xmc0_9:2 */
	83,	/* xmc0_10:2 */
	86,	/* xmc0_11:2 */
	89,	/* xmc0_12:2 */
	109,	/* xmc1_0:2 */
	112,	/* xmc1_1:2 */
	115,	/* xmc1_2:2 */
	118,	/* xmc1_3:2 */
	121,	/* xmc1_4:2 */
	124,	/* xmc1_5:2 */
	127,	/* xmc1_6:2 */
	130,	/* xmc1_7:2 */
	133,	/* xmc1_8:2 */
	136,	/* xmc1_9:2 */
	139,	/* xmc1_10:2 */
	142,	/* xmc1_11:2 */
	145,	/* xmc1_12:2 */
	165,	/* xmc2_0:2 */
	168,	/* xmc2_1:2 */
	171,	/* xmc2_2:2 */
	174,	/* xmc2_3:2 */
	177,	/* xmc2_4:2 */
	180,	/* xmc2_5:2 */
	183,	/* xmc2_6:2 */
	186,	/* xmc2_7:2 */
	189,	/* xmc2_8:2 */
	192,	/* xmc2_9:2 */
	195,	/* xmc2_10:2 */
	198,	/* xmc2_11:2 */
	201,	/* xmc2_12:2 */
	221,	/* xmc3_0:2 */
	224,	/* xmc3_1:2 */
	227,	/* xmc3_2:2 */
	230,	/* xmc3_3:2 */
	233,	/* xmc3_4:2 */
	236,	/* xmc3_5:2 */
	239,	/* xmc3_6:2 */
	242,	/* xmc3_7:2 */
	245,	/* xmc3_8:2 */
	248,	/* xmc3_9:2 */
	251,	/* xmc3_10:2 */
	254,	/* xmc3_11:2 */
	257,	/* xmc3_12:2 */
	46,	/* Mc0:0 */
	102,	/* Mc1:0 */
	158,	/* Mc2:0 */
	214,	/* Mc3:0 */
	51,	/* Xmaxc0:1 */
	107,	/* Xmaxc1:1 */
	163,	/* Xmaxc2:1 */
	219,	/* Xmaxc3:1 */
	54,	/* xmc0_0:1 */
	57,	/* xmc0_1:1 */
	60,	/* xmc0_2:1 */
	63,	/* xmc0_3:1 */
	66,	/* xmc0_4:1 */
	69,	/* xmc0_5:1 */
	72,	/* xmc0_6:1 */
	75,	/* xmc0_7:1 */
	78,	/* xmc0_8:1 */
	81,	/* xmc0_9:1 */
	84,	/* xmc0_10:1 */
	87,	/* xmc0_11:1 */
	90,	/* xmc0_12:1 */
	110,	/* xmc1_0:1 */
	113,	/* xmc1_1:1 */
	116,	/* xmc1_2:1 */
	119,	/* xmc1_3:1 */
	122,	/* xmc1_4:1 */
	125,	/* xmc1_5:1 */
	128,	/* xmc1_6:1 */
	131,	/* xmc1_7:1 */
	134,	/* xmc1_8:1 */
	137,	/* xmc1_9:1 */
	140,	/* xmc1_10:1 */
	143,	/* xmc1_11:1 */
	146,	/* xmc1_12:1 */
	166,	/* xmc2_0:1 */
	169,	/* xmc2_1:1 */
	172,	/* xmc2_2:1 */
	175,	/* xmc2_3:1 */
	178,	/* xmc2_4:1 */
	181,	/* xmc2_5:1 */
	184,	/* xmc2_6:1 */
	187,	/* xmc2_7:1 */
	190,	/* xmc2_8:1 */
	193,	/* xmc2_9:1 */
	196,	/* xmc2_10:1 */
	199,	/* xmc2_11:1 */
	202,	/* xmc2_12:1 */
	222,	/* xmc3_0:1 */
	225,	/* xmc3_1:1 */
	228,	/* xmc3_2:1 */
	231,	/* xmc3_3:1 */
	234,	/* xmc3_4:1 */
	237,	/* xmc3_5:1 */
	240,	/* xmc3_6:1 */
	243,	/* xmc3_7:1 */
	246,	/* xmc3_8:1 */
	249,	/* xmc3_9:1 */
	252,	/* xmc3_10:1 */
	255,	/* xmc3_11:1 */
	258,	/* xmc3_12:1 */
	5,	/* LARc0:0 */
	10,	/* LARc1:1 */
	15,	/* LARc2:1 */
	28,	/* LARc5:1 */
	32,	/* LARc6:0 */
	34,	/* LARc7:1 */
	35,	/* LARc7:0 */
	16,	/* LARc2:0 */
	20,	/* LARc3:1 */
	21,	/* LARc3:0 */
	25,	/* LARc4:0 */
	52,	/* Xmaxc0:0 */
	108,	/* Xmaxc1:0 */
	164,	/* Xmaxc2:0 */
	220,	/* Xmaxc3:0 */
	55,	/* xmc0_0:0 */
	58,	/* xmc0_1:0 */
	61,	/* xmc0_2:0 */
	64,	/* xmc0_3:0 */
	67,	/* xmc0_4:0 */
	70,	/* xmc0_5:0 */
	73,	/* xmc0_6:0 */
	76,	/* xmc0_7:0 */
	79,	/* xmc0_8:0 */
	82,	/* xmc0_9:0 */
	85,	/* xmc0_10:0 */
	88,	/* xmc0_11:0 */
	91,	/* xmc0_12:0 */
	111,	/* xmc1_0:0 */
	114,	/* xmc1_1:0 */
	117,	/* xmc1_2:0 */
	120,	/* xmc1_3:0 */
	123,	/* xmc1_4:0 */
	126,	/* xmc1_5:0 */
	129,	/* xmc1_6:0 */
	132,	/* xmc1_7:0 */
	135,	/* xmc1_8:0 */
	138,	/* xmc1_9:0 */
	141,	/* xmc1_10:0 */
	144,	/* xmc1_11:0 */
	147,	/* xmc1_12:0 */
	167,	/* xmc2_0:0 */
	170,	/* xmc2_1:0 */
	173,	/* xmc2_2:0 */
	176,	/* xmc2_3:0 */
	179,	/* xmc2_4:0 */
	182,	/* xmc2_5:0 */
	185,	/* xmc2_6:0 */
	188,	/* xmc2_7:0 */
	191,	/* xmc2_8:0 */
	194,	/* xmc2_9:0 */
	197,	/* xmc2_10:0 */
	200,	/* xmc2_11:0 */
	203,	/* xmc2_12:0 */
	223,	/* xmc3_0:0 */
	226,	/* xmc3_1:0 */
	229,	/* xmc3_2:0 */
	232,	/* xmc3_3:0 */
	235,	/* xmc3_4:0 */
	238,	/* xmc3_5:0 */
	241,	/* xmc3_6:0 */
	244,	/* xmc3_7:0 */
	247,	/* xmc3_8:0 */
	250,	/* xmc3_9:0 */
	253,	/* xmc3_10:0 */
	256,	/* xmc3_11:0 */
	259,	/* xmc3_12:0 */
	11,	/* LARc1:0 */
	29,	/* LARc5:0 */
};

static int
msb_get_bit(buf, bn)
	u_char *buf;
{
	int pos_byte = bn >> 3;
	int pos_bit  = 7 - (bn & 7);

	return (buf[pos_byte] >> pos_bit) & 1;
}

static void
msb_set_bit(buf, bn, bit)
	u_char *buf;
{
	int pos_byte = bn >> 3;
	int pos_bit  = 7 - (bn & 7);

	buf[pos_byte] |= (bit << pos_bit);
}

void
gsm0610_tidsp_to_libgsm(inbytes, outbytes)
	u_char *inbytes, *outbytes;
{
	int i, di, si;

	bzero(outbytes, 33);
	outbytes[0] = 0xD0;
	for (i = 0; i < 260; i++) {
		di = gsm0610_bitorder[i];
		si = (i > 181) ? i + 4 : i;
		msb_set_bit(outbytes, 4 + di, msb_get_bit(inbytes, si));
        }
}

void
gsm0610_libgsm_to_tidsp(inbytes, outbytes)
	u_char *inbytes, *outbytes;
{
	int i, di, si;

	bzero(outbytes, 33);
	for (i = 0; i < 260; i++) {
		si = gsm0610_bitorder[i];
		di = (i > 181) ? i + 4 : i;
		msb_set_bit(outbytes, di, msb_get_bit(inbytes, 4 + si));
        }
}