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ffmpeg / libavcodec / ra144.c @ 11bb2eb0

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/*
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 * Real Audio 1.0 (14.4K)
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 * Copyright (c) 2003 the ffmpeg project
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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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#include "avcodec.h"
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#include "bitstream.h"
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#include "ra144.h"
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#define NBLOCKS         4       /* number of segments within a block */
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#define BLOCKSIZE       40      /* (quarter) block size in 16-bit words (80 bytes) */
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#define HALFBLOCK       20      /* BLOCKSIZE/2 */
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#define BUFFERSIZE      146     /* for do_output */
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/* internal globals */
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typedef struct {
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    unsigned int     old_energy;        ///< previous frame energy
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    /* the swapped buffers */
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    unsigned int     lpc_tables[4][10];
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    unsigned int    *lpc_refl;          ///< LPC reflection coefficients
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    unsigned int    *lpc_coef;          ///< LPC coefficients
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    unsigned int    *lpc_refl_old;      ///< previous frame LPC reflection coefs
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    unsigned int    *lpc_coef_old;      ///< previous frame LPC coefficients
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    unsigned int buffer[5];
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    uint16_t adapt_cb[148];             ///< adaptive codebook
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} RA144Context;
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static int ra144_decode_init(AVCodecContext * avctx)
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{
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    RA144Context *ractx = avctx->priv_data;
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    ractx->lpc_refl     = ractx->lpc_tables[0];
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    ractx->lpc_coef     = ractx->lpc_tables[1];
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    ractx->lpc_refl_old = ractx->lpc_tables[2];
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    ractx->lpc_coef_old = ractx->lpc_tables[3];
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    return 0;
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}
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/**
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 * Evaluate sqrt(x << 24). x must fit in 20 bits. This value is evaluated in an
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 * odd way to make the output identical to the binary decoder.
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 */
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static int t_sqrt(unsigned int x)
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{
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    int s = 0;
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    while (x > 0xfff) {
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        s++;
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        x = x >> 2;
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    }
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    return (ff_sqrt(x << 20) << s) << 2;
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}
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/**
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 * Evaluate the LPC filter coefficients from the reflection coefficients.
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 * Does the inverse of the eval_refl() function.
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 */
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static void eval_coefs(const int *refl, int *coefs)
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{
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    int buffer[10];
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    int *b1 = buffer;
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    int *b2 = coefs;
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    int x, y;
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    for (x=0; x < 10; x++) {
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        b1[x] = refl[x] << 4;
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        for (y=0; y < x; y++)
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            b1[y] = ((refl[x] * b2[x-y-1]) >> 12) + b2[y];
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        FFSWAP(int *, b1, b2);
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    }
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    for (x=0; x < 10; x++)
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        coefs[x] >>= 4;
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}
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/* rotate block */
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static void rotate_block(const int16_t *source, int16_t *target, int offset)
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{
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    int i=0, k=0;
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    source += BUFFERSIZE - offset;
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    while (i<BLOCKSIZE) {
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        target[i++] = source[k++];
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        if (k == offset)
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            k = 0;
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    }
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}
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/* inverse root mean square */
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static int irms(const int16_t *data, int factor)
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{
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    unsigned int i, sum = 0;
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    for (i=0; i < BLOCKSIZE; i++)
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        sum += data[i] * data[i];
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    if (sum == 0)
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        return 0; /* OOPS - division by zero */
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    return (0x20000000 / (t_sqrt(sum) >> 8)) * factor;
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}
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/* multiply/add wavetable */
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static void add_wav(int n, int skip_first, int *m, const int16_t *s1,
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                    const int8_t *s2, const int8_t *s3, int16_t *dest)
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{
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    int i;
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    int v[3];
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    v[0] = 0;
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    for (i=!skip_first; i<3; i++)
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        v[i] = (wavtable1[n][i] * m[i]) >> (wavtable2[n][i] + 1);
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    for (i=0; i < BLOCKSIZE; i++)
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        dest[i] = ((*(s1++))*v[0] + (*(s2++))*v[1] + (*(s3++))*v[2]) >> 12;
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}
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static void final(const int16_t *i1, const int16_t *i2,
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                  void *out, int *statbuf, int len)
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{
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    int x, i;
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    uint16_t work[50];
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    int16_t *ptr = work;
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    memcpy(work, statbuf,20);
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    memcpy(work + 10, i2, len * 2);
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    for (i=0; i<len; i++) {
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        int sum = 0;
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        int new_val;
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        for(x=0; x<10; x++)
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            sum += i1[9-x] * ptr[x];
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        sum >>= 12;
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        new_val = ptr[10] - sum;
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        if (new_val < -32768 || new_val > 32767) {
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            memset(out, 0, len * 2);
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            memset(statbuf, 0, 20);
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            return;
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        }
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        ptr[10] = new_val;
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        ptr++;
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    }
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    memcpy(out, work+10, len * 2);
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    memcpy(statbuf, work + 40, 20);
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}
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static unsigned int rescale_rms(int rms, int energy)
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{
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    return (rms * energy) >> 10;
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}
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static unsigned int rms(const int *data)
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{
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    int x;
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    unsigned int res = 0x10000;
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    int b = 0;
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    for (x=0; x<10; x++) {
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        res = (((0x1000000 - (*data) * (*data)) >> 12) * res) >> 12;
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        if (res == 0)
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            return 0;
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        while (res <= 0x3fff) {
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            b++;
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            res <<= 2;
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        }
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        data++;
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    }
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    if (res > 0)
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        res = t_sqrt(res);
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    res >>= (b + 10);
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    return res;
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}
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/* do quarter-block output */
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static void do_output_subblock(RA144Context *ractx,
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                               const uint16_t  *lpc_coefs, unsigned int gval,
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                               int16_t *output_buffer, GetBitContext *gb)
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{
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    uint16_t buffer_a[40];
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    uint16_t *block;
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    int cba_idx = get_bits(gb, 7); // index of the adaptive CB, 0 if none
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    int gain    = get_bits(gb, 8);
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    int cb1_idx = get_bits(gb, 7);
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    int cb2_idx = get_bits(gb, 7);
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    int m[3];
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    if (cba_idx) {
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        cba_idx += HALFBLOCK - 1;
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        rotate_block(ractx->adapt_cb, buffer_a, cba_idx);
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        m[0] = irms(buffer_a, gval) >> 12;
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    } else {
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        m[0] = 0;
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    }
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    m[1] = ((ftable1[cb1_idx] >> 4) * gval) >> 8;
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    m[2] = ((ftable2[cb2_idx] >> 4) * gval) >> 8;
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    memmove(ractx->adapt_cb, ractx->adapt_cb + BLOCKSIZE,
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            (BUFFERSIZE - BLOCKSIZE) * 2);
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    block = ractx->adapt_cb + BUFFERSIZE - BLOCKSIZE;
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    add_wav(gain, cba_idx, m, buffer_a, etable1[cb1_idx], etable2[cb2_idx],
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            block);
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    final(lpc_coefs, block, output_buffer, ractx->buffer, BLOCKSIZE);
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}
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static void int_to_int16(int16_t *decsp, const int *inp)
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{
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    int i;
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    for (i=0; i<30; i++)
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        *(decsp++) = *(inp++);
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}
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/**
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 * Evaluate the reflection coefficients from the filter coefficients.
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 * Does the inverse of the eval_coefs() function.
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 *
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 * @return 1 if one of the reflection coefficients is of magnitude greater than
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 *         4095, 0 if not.
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 */
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static int eval_refl(const int16_t *coefs, int *refl, RA144Context *ractx)
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{
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    int retval = 0;
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    int b, c, i;
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    unsigned int u;
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    int buffer1[10];
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    int buffer2[10];
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    int *bp1 = buffer1;
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    int *bp2 = buffer2;
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    for (i=0; i < 10; i++)
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        buffer2[i] = coefs[i];
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    u = refl[9] = bp2[9];
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    if (u + 0x1000 > 0x1fff) {
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        av_log(ractx, AV_LOG_ERROR, "Overflow. Broken sample?\n");
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        return 0;
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    }
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    for (c=8; c >= 0; c--) {
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        if (u == 0x1000)
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            u++;
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        if (u == 0xfffff000)
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            u--;
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        b = 0x1000-((u * u) >> 12);
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        if (b == 0)
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            b++;
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        for (u=0; u<=c; u++)
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            bp1[u] = ((bp2[u] - ((refl[c+1] * bp2[c-u]) >> 12)) * (0x1000000 / b)) >> 12;
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        refl[c] = u = bp1[c];
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        if ((u + 0x1000) > 0x1fff)
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            retval = 1;
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        FFSWAP(int *, bp1, bp2);
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    }
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    return retval;
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}
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static int interp(RA144Context *ractx, int16_t *decsp, int block_num,
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                  int copynew, int energy)
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{
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    int work[10];
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    int a = block_num + 1;
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    int b = NBLOCKS - a;
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    int x;
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    // Interpolate block coefficients from the this frame forth block and
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    // last frame forth block
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    for (x=0; x<30; x++)
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        decsp[x] = (a * ractx->lpc_coef[x] + b * ractx->lpc_coef_old[x])>> 2;
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    if (eval_refl(decsp, work, ractx)) {
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        // The interpolated coefficients are unstable, copy either new or old
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        // coefficients
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        if (copynew) {
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            int_to_int16(decsp, ractx->lpc_coef);
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            return rescale_rms(rms(ractx->lpc_refl), energy);
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        } else {
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            int_to_int16(decsp, ractx->lpc_coef_old);
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            return rescale_rms(rms(ractx->lpc_refl_old), energy);
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        }
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    } else {
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        return rescale_rms(rms(work), energy);
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    }
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}
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/* Uncompress one block (20 bytes -> 160*2 bytes) */
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static int ra144_decode_frame(AVCodecContext * avctx,
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                              void *vdata, int *data_size,
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                              const uint8_t * buf, int buf_size)
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{
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    static const uint8_t sizes[10] = {6, 5, 5, 4, 4, 3, 3, 3, 3, 2};
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    unsigned int refl_rms[4];  // RMS of the reflection coefficients
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    uint16_t block_coefs[4][30]; // LPC coefficients of each sub-block
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    int i, c;
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    int16_t *data = vdata;
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    unsigned int energy;
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    RA144Context *ractx = avctx->priv_data;
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    GetBitContext gb;
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    if(buf_size < 20) {
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        av_log(avctx, AV_LOG_ERROR,
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               "Frame too small (%d bytes). Truncated file?\n", buf_size);
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        return buf_size;
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    }
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    init_get_bits(&gb, buf, 20 * 8);
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    for (i=0; i<10; i++)
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        // "<< 1"? Doesn't this make one value out of two of the table useless?
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        ractx->lpc_refl[i] = decodetable[i][get_bits(&gb, sizes[i]) << 1];
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    eval_coefs(ractx->lpc_refl, ractx->lpc_coef);
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    energy = decodeval[get_bits(&gb, 5) << 1]; // Useless table entries?
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    refl_rms[0] = interp(ractx, block_coefs[0], 0, 0, ractx->old_energy);
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    refl_rms[1] = interp(ractx, block_coefs[1], 1, energy > ractx->old_energy,
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                    t_sqrt(energy*ractx->old_energy) >> 12);
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    refl_rms[2] = interp(ractx, block_coefs[2], 2, 1, energy);
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    refl_rms[3] = rescale_rms(rms(ractx->lpc_refl), energy);
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    int_to_int16(block_coefs[3], ractx->lpc_coef);
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    /* do output */
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    for (c=0; c<4; c++) {
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        do_output_subblock(ractx, block_coefs[c], refl_rms[c], data, &gb);
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        for (i=0; i<BLOCKSIZE; i++) {
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            *data = av_clip_int16(*data << 2);
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            data++;
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        }
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    }
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    ractx->old_energy = energy;
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    FFSWAP(unsigned int *, ractx->lpc_refl_old, ractx->lpc_refl);
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    FFSWAP(unsigned int *, ractx->lpc_coef_old, ractx->lpc_coef);
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    *data_size = 2*160;
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    return 20;
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}
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AVCodec ra_144_decoder =
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{
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    "real_144",
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    CODEC_TYPE_AUDIO,
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    CODEC_ID_RA_144,
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    sizeof(RA144Context),
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    ra144_decode_init,
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    NULL,
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    NULL,
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    ra144_decode_frame,
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    .long_name = "RealAudio 1.0 (14.4K)",
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};