FreeCalypso > hg > gsm-codec-lib
view libgsmefr/enc_lag6.c @ 216:9d59df9b0e4e
amrconv: new program amr-ietf2cod
author | Mychaela Falconia <falcon@freecalypso.org> |
---|---|
date | Fri, 21 Apr 2023 21:28:02 +0000 |
parents | f151d6c18b31 |
children |
line wrap: on
line source
/************************************************************************* * * FUNCTION: Enc_lag6 * * PURPOSE: Encoding of fractional pitch lag with 1/6 resolution. * * DESCRIPTION: * First and third subframes: * -------------------------- * The pitch range is divided as follows: * 17 3/6 to 94 3/6 resolution 1/6 * 95 to 143 resolution 1 * * The period is encoded with 9 bits. * For the range with fractions: * index = (T-17)*6 + frac - 3; * where T=[17..94] and frac=[-2,-1,0,1,2,3] * and for the integer only range * index = (T - 95) + 463; where T=[95..143] * * Second and fourth subframes: * ---------------------------- * For the 2nd and 4th subframes a resolution of 1/6 is always used, * and the search range is relative to the lag in previous subframe. * If t0 is the lag in the previous subframe then * t_min=t0-5 and t_max=t0+4 and the range is given by * (t_min-1) 3/6 to (t_max) 3/6 * * The period in the 2nd (and 4th) subframe is encoded with 6 bits: * index = (T-(t_min-1))*6 + frac - 3; * where T=[t_min-1..t_max] and frac=[-2,-1,0,1,2,3] * * Note that only 61 values are used. If the decoder receives 61, 62, * or 63 as the relative pitch index, it means that a transmission * error occurred and the pitch from previous subframe should be used. * *************************************************************************/ #include "gsm_efr.h" #include "typedef.h" #include "namespace.h" #include "basic_op.h" #include "no_count.h" #include "codec.h" Word16 Enc_lag6 ( /* output: Return index of encoding */ Word16 T0, /* input : Pitch delay */ Word16 *T0_frac, /* in/out: Fractional pitch delay */ Word16 *T0_min, /* in/out: Minimum search delay */ Word16 *T0_max, /* in/out: Maximum search delay */ Word16 pit_min, /* input : Minimum pitch delay */ Word16 pit_max, /* input : Maximum pitch delay */ Word16 pit_flag /* input : Flag for 1st or 3rd subframe */ ) { Word16 index, i; test (); if (pit_flag == 0) /* if 1st or 3rd subframe */ { /* encode pitch delay (with fraction) */ test (); if (T0 <= 94) { /* index = T0*6 - 105 + *T0_frac */ i = add (add (T0, T0), T0); index = add (sub (add (i, i), 105), *T0_frac); } else { /* set fraction to 0 for delays > 94 */ *T0_frac = 0; move16 (); index = add (T0, 368); } /* find T0_min and T0_max for second (or fourth) subframe */ *T0_min = sub (T0, 5); move16 (); test (); if (*T0_min < pit_min) { *T0_min = pit_min; move16 (); } *T0_max = add (*T0_min, 9); test (); if (*T0_max > pit_max) { *T0_max = pit_max; move16 (); *T0_min = sub (*T0_max, 9); move16 (); } } else /* if second or fourth subframe */ { /* index = 6*(T0-*T0_min) + 3 + *T0_frac */ i = sub (T0, *T0_min); i = add (add (i, i), i); index = add (add (add (i, i), 3), *T0_frac); } return index; }