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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@20901 a1c6a512-1295-4272-9138-f99709370657
243 lines
7.3 KiB
C
243 lines
7.3 KiB
C
/*
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* COOK compatible decoder, fixed point implementation.
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* Copyright (c) 2007 Ian Braithwaite
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*
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*/
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/**
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* @file cook_float.h
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*
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* Cook AKA RealAudio G2 fixed point functions.
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*
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* Fixed point values are represented as 32 bit signed integers,
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* which can be added and subtracted directly in C (without checks for
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* overflow/saturation.
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* Two multiplication routines are provided:
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* 1) Multiplication by powers of two (2^-31 .. 2^31), implemented
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* with C's bit shift operations.
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* 2) Multiplication by 16 bit fractions (0 <= x < 1), implemented
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* in C using two 32 bit integer multiplications.
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*/
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/**
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* Initialise fixed point implementation.
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* Nothing to do for fixed point.
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*
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* @param q pointer to the COOKContext
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*/
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static inline int init_cook_math(COOKContext *q)
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{
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return 0;
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}
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/**
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* Free resources used by floating point implementation.
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* Nothing to do for fixed point.
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*
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* @param q pointer to the COOKContext
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*/
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static inline void free_cook_math(COOKContext *q)
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{
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return;
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}
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/**
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* Fixed point multiply by power of two.
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*
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* @param x fix point value
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* @param i integer power-of-two, -31..+31
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*/
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static inline FIXP fixp_pow2(FIXP x, int i)
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{
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if (i < 0)
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return (x >> -i) + ((x >> (-i-1)) & 1);
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else
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return x << i; /* no check for overflow */
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}
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/**
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* Fixed point multiply by fraction.
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*
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* @param a fix point value
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* @param b fix point fraction, 0 <= b < 1
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*/
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static inline FIXP fixp_mult_su(FIXP a, FIXPU b)
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{
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int32_t hb = (a >> 16) * b;
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uint32_t lb = (a & 0xffff) * b;
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return hb + (lb >> 16) + ((lb & 0x8000) >> 15);
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}
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/**
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* The real requantization of the mltcoefs
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*
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* @param q pointer to the COOKContext
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* @param index index
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* @param quant_index quantisation index for this band
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* @param subband_coef_index array of indexes to quant_centroid_tab
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* @param subband_coef_sign use random noise instead of predetermined value
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* @param mlt_ptr pointer to the mlt coefficients
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*/
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static void scalar_dequant_math(COOKContext *q, int index,
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int quant_index, int* subband_coef_index,
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int* subband_coef_sign, REAL_T *mlt_p)
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{
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/* Num. half bits to right shift */
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const int s = 33 - quant_index + av_log2(q->samples_per_channel);
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const FIXP *table = quant_tables[s & 1][index];
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FIXP f;
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int i;
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for(i=0 ; i<SUBBAND_SIZE ; i++) {
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f = table[subband_coef_index[i]];
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/* noise coding if subband_coef_index[i] == 0 */
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if (((subband_coef_index[i] == 0) && av_lfg_get(&q->random_state) < 0x80000000) ||
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((subband_coef_index[i] != 0) && subband_coef_sign[i]))
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f = -f;
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mlt_p[i] = (s >= 64) ? 0 : fixp_pow2(f, -(s/2));
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}
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}
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/**
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* The modulated lapped transform, this takes transform coefficients
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* and transforms them into timedomain samples.
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* A window step is also included.
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*
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* @param q pointer to the COOKContext
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* @param inbuffer pointer to the mltcoefficients
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* @param outbuffer pointer to the timedomain buffer
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* @param mlt_tmp pointer to temporary storage space
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*/
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#include "cook_fixp_mdct.h"
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static inline void imlt_math(COOKContext *q, FIXP *in)
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{
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const int n = q->samples_per_channel;
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const int step = 4 << (10 - av_log2(n));
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int i = 0, j = step>>1;
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cook_mdct_backward(2 * n, in, q->mono_mdct_output);
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do {
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FIXP tmp = q->mono_mdct_output[i];
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q->mono_mdct_output[i] =
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fixp_mult_su(-q->mono_mdct_output[n + i], sincos_lookup[j]);
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q->mono_mdct_output[n + i] = fixp_mult_su(tmp, sincos_lookup[j+1]);
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j += step;
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} while (++i < n/2);
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do {
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FIXP tmp = q->mono_mdct_output[i];
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j -= step;
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q->mono_mdct_output[i] =
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fixp_mult_su(-q->mono_mdct_output[n + i], sincos_lookup[j+1]);
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q->mono_mdct_output[n + i] = fixp_mult_su(tmp, sincos_lookup[j]);
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} while (++i < n);
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}
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/**
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* Perform buffer overlapping.
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*
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* @param q pointer to the COOKContext
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* @param gain gain correction to apply first to output buffer
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* @param buffer data to overlap
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*/
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static inline void overlap_math(COOKContext *q, int gain, FIXP buffer[])
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{
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int i;
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for(i=0 ; i<q->samples_per_channel ; i++) {
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q->mono_mdct_output[i] =
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fixp_pow2(q->mono_mdct_output[i], gain) + buffer[i];
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}
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}
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/**
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* the actual requantization of the timedomain samples
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*
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* @param q pointer to the COOKContext
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* @param buffer pointer to the timedomain buffer
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* @param gain_index index for the block multiplier
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* @param gain_index_next index for the next block multiplier
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*/
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static inline void
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interpolate_math(COOKContext *q, FIXP* buffer,
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int gain_index, int gain_index_next)
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{
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int i;
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int gain_size_factor = q->samples_per_channel / 8;
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if(gain_index == gain_index_next){ //static gain
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for(i = 0; i < gain_size_factor; i++) {
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buffer[i] = fixp_pow2(buffer[i], gain_index);
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}
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} else { //smooth gain
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int step = (gain_index_next - gain_index)
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<< (7 - av_log2(gain_size_factor));
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int x = 0;
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for(i = 0; i < gain_size_factor; i++) {
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buffer[i] = fixp_mult_su(buffer[i], pow128_tab[x]);
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buffer[i] = fixp_pow2(buffer[i], gain_index+1);
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x += step;
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gain_index += (x + 128) / 128 - 1;
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x = (x + 128) % 128;
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}
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}
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}
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/**
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* Decoupling calculation for joint stereo coefficients.
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*
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* @param x mono coefficient
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* @param table number of decoupling table
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* @param i table index
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*/
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static inline FIXP cplscale_math(FIXP x, int table, int i)
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{
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return fixp_mult_su(x, cplscales[table-2][i]);
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}
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/**
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* Final converion from floating point values to
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* signed, 16 bit sound samples. Round and clip.
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*
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* @param q pointer to the COOKContext
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* @param out pointer to the output buffer
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* @param chan 0: left or single channel, 1: right channel
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*/
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static inline void output_math(COOKContext *q, int16_t *out, int chan)
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{
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int j;
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for (j = 0; j < q->samples_per_channel; j++) {
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out[chan + q->nb_channels * j] =
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av_clip(fixp_pow2(q->mono_mdct_output[j], -11), -32768, 32767);
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}
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}
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