FreeCalypso > hg > gsm-codec-lib
view libtwamr/pow2.c @ 477:4c9222d95647
libtwamr encoder: always emit frame->mode = mode;
In the original implementation of amr_encode_frame(), the 'mode' member
of the output struct was set to 0xFF if the output frame type is TX_NO_DATA.
This design was made to mimic the mode field (16-bit word) being set to
0xFFFF (or -1) in 3GPP test sequence format - but nothing actually depends
on this struct member being set in any way, and amr_frame_to_tseq()
generates the needed 0xFFFF on its own, based on frame->type being equal
to TX_NO_DATA.
It is simpler and more efficient to always set frame->mode to the actual
encoding mode in amr_encode_frame(), and this new behavior has already
been documented in doc/AMR-library-API description in anticipation of
the present change.
| author | Mychaela Falconia <falcon@freecalypso.org> |
|---|---|
| date | Sat, 18 May 2024 22:30:42 +0000 |
| parents | 190c4c9a3693 |
| children |
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/* ******************************************************************************** * * GSM AMR-NB speech codec R98 Version 7.6.0 December 12, 2001 * R99 Version 3.3.0 * REL-4 Version 4.1.0 * ******************************************************************************** * * File : pow2.c * Purpose : computes L_x = pow(2.0, exponent.fraction) * ******************************************************************************** */ /* ******************************************************************************** * MODULE INCLUDE FILE AND VERSION ID ******************************************************************************** */ #include "namespace.h" #include "pow2.h" /* ******************************************************************************** * INCLUDE FILES ******************************************************************************** */ #include "typedef.h" #include "basic_op.h" #include "no_count.h" /* ******************************************************************************** * LOCAL VARIABLES AND TABLES ******************************************************************************** */ #include "pow2.tab" /* Table for Pow2() */ /* ******************************************************************************** * PUBLIC PROGRAM CODE ******************************************************************************** */ /************************************************************************* * * FUNCTION: Pow2() * * PURPOSE: computes L_x = pow(2.0, exponent.fraction) * * DESCRIPTION: * The function Pow2(L_x) is approximated by a table and linear * interpolation. * 1- i = bit10-b15 of fraction, 0 <= i <= 31 * 2- a = bit0-b9 of fraction * 3- L_x = table[i]<<16 - (table[i] - table[i+1]) * a * 2 * 4- L_x = L_x >> (30-exponent) (with rounding) * *************************************************************************/ Word32 Pow2 ( /* (o) : result (range: 0<=val<=0x7fffffff) */ Word16 exponent, /* (i) : Integer part. (range: 0<=val<=30) */ Word16 fraction /* (i) : Fractional part. (range: 0.0<=val<1.0) */ ) { Word16 exp, i, a, tmp; Word32 L_x; L_x = L_mult (fraction, 32);/* L_x = fraction<<6 */ i = extract_h (L_x); /* Extract b10-b16 of fraction */ L_x = L_shr (L_x, 1); a = extract_l (L_x); /* Extract b0-b9 of fraction */ a = a & (Word16) 0x7fff; logic16 (); L_x = L_deposit_h (table[i]); /* table[i] << 16 */ tmp = sub (table[i], table[i + 1]); /* table[i] - table[i+1] */ L_x = L_msu (L_x, tmp, a); /* L_x -= tmp*a*2 */ exp = sub (30, exponent); L_x = L_shr_r (L_x, exp); return (L_x); }