libavcodec/ra288.c

   1 /*
   2  * RealAudio 2.0 (28.8K)
   3  * Copyright (c) 2003 the ffmpeg project
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #include "avcodec.h"
  23 #define ALT_BITSTREAM_READER_LE
  24 #include "bitstream.h"
  25 #include "ra288.h"
  26 #include "lpc.h"
  27
  28 typedef struct {
  29     float sp_lpc[36];      ///< LPC coefficients for speech data (spec: A)
  30     float gain_lpc[10];    ///< LPC coefficients for gain        (spec: GB)
  31
  32     float sp_hist[111];    ///< speech data history              (spec: SB)
  33
  34     /// speech part of the gain autocorrelation                  (spec: REXP)
  35     float sp_rec[37];
  36
  37     float gain_hist[38];   ///< log-gain history                 (spec: SBLG)
  38
  39     /// recursive part of the gain autocorrelation               (spec: REXPLG)
  40     float gain_rec[11];
  41
  42     float sp_block[41];    ///< four blocks of speech data       (spec: STTMP)
  43     float gain_block[10];  ///< four blocks of gain data         (spec: GSTATE)
  44 } RA288Context;
  45
  46 static av_cold int ra288_decode_init(AVCodecContext *avctx)
  47 {
  48     avctx->sample_fmt = SAMPLE_FMT_S16;
  49     return 0;
  50 }
  51
  52 static inline float scalar_product_float(const float * v1, const float * v2,
  53                                          int size)
  54 {
  55     float res = 0.;
  56
  57     while (size--)
  58         res += *v1++ * *v2++;
  59
  60     return res;
  61 }
  62
  63 static void apply_window(float *tgt, const float *m1, const float *m2, int n)
  64 {
  65     while (n--)
  66         *tgt++ = *m1++ * *m2++;
  67 }
  68
  69 static void decode(RA288Context *ractx, float gain, int cb_coef)
  70 {
  71     int i, j;
  72     double sumsum;
  73     float sum, buffer[5];
  74     float *block = ractx->sp_block + 36; // current block
  75
  76     memmove(ractx->sp_block, ractx->sp_block + 5, 36*sizeof(*ractx->sp_block));
  77
  78     for (i=0; i < 5; i++) {
  79         block[i] = 0.;
  80         for (j=0; j < 36; j++)
  81             block[i] -= block[i-1-j]*ractx->sp_lpc[j];
  82     }
  83
  84     /* block 46 of G.728 spec */
  85     sum = 32.;
  86     for (i=0; i < 10; i++)
  87         sum -= ractx->gain_block[9-i] * ractx->gain_lpc[i];
  88
  89     /* block 47 of G.728 spec */
  90     sum = av_clipf(sum, 0, 60);
  91
  92     /* block 48 of G.728 spec */
  93     sumsum = exp(sum * 0.1151292546497) * gain; /* pow(10.0,sum/20)*gain */
  94
  95     for (i=0; i < 5; i++)
  96         buffer[i] = codetable[cb_coef][i] * sumsum * (1./2048.);
  97
  98     sum = scalar_product_float(buffer, buffer, 5) / 5;
  99
 100     sum = FFMAX(sum, 1);
 101
 102     /* shift and store */
 103     memmove(ractx->gain_block, ractx->gain_block + 1,
 104             9 * sizeof(*ractx->gain_block));
 105
 106     ractx->gain_block[9] = 10 * log10(sum) - 32;
 107
 108     for (i=1; i < 5; i++)
 109         for (j=i-1; j >= 0; j--)
 110             buffer[i] -= ractx->sp_lpc[i-j-1] * buffer[j];
 111
 112     /* output */
 113     for (i=0; i < 5; i++)
 114         block[i] = av_clipf(block[i] + buffer[i], -4095, 4095);
 115 }
 116
 117 static void convolve(float *tgt, const float *src, int len, int n)
 118 {
 119     for (; n >= 0; n--)
 120         tgt[n] = scalar_product_float(src, src - n, len);
 121
 122 }
 123
 124 /**
 125  * Hybrid window filtering, see blocks 36 and 49 of the G.728 specification.
 126  *
 127  * @param order   filter order
 128  * @param n       input length
 129  * @param non_rec number of non-recursive samples
 130  * @param out     filter output
 131  * @param in      pointer to the input of the filter
 132  * @param hist    Pointer to the input history of the filter, it is updated by
 133  *                this function.
 134  * @param out     pointer to the non-recursive part of the output
 135  * @param out2    pointer to the recursive part of the output
 136  * @param window  pointer to the windowing function table
 137  */
 138 static void do_hybrid_window(int order, int n, int non_rec, const float *in,
 139                              float *out, float *hist, float *out2,
 140                              const float *window)
 141 {
 142     int i;
 143     float buffer1[order + 1];
 144     float buffer2[order + 1];
 145     float work[order + n + non_rec];
 146
 147     /* update history */
 148     memmove(hist                  , hist + n, (order + non_rec)*sizeof(*hist));
 149     memcpy (hist + order + non_rec, in      , n                *sizeof(*hist));
 150
 151     apply_window(work, window, hist, order + n + non_rec);
 152
 153     convolve(buffer1, work + order    , n      , order);
 154     convolve(buffer2, work + order + n, non_rec, order);
 155
 156     for (i=0; i <= order; i++) {
 157         out2[i] = out2[i] * 0.5625 + buffer1[i];
 158         out [i] = out2[i]          + buffer2[i];
 159     }
 160
 161     /* Multiply by the white noise correcting factor (WNCF). */
 162     *out *= 257./256.;
 163 }
 164
 165 /**
 166  * Backward synthesis filter, find the LPC coefficients from past speech data.
 167  */
 168 static void backward_filter(RA288Context *ractx)
 169 {
 170     float temp1[37]; // RTMP in the spec
 171     float temp2[11]; // GPTPMP in the spec
 172
 173     do_hybrid_window(36, 40, 35, ractx->sp_block+1, temp1, ractx->sp_hist,
 174                      ractx->sp_rec, syn_window);
 175
 176     if (!compute_lpc_coefs(temp1, 36, ractx->sp_lpc, 0, 1, 1))
 177         apply_window(ractx->sp_lpc, ractx->sp_lpc, syn_bw_tab, 36);
 178
 179     do_hybrid_window(10, 8, 20, ractx->gain_block+2, temp2, ractx->gain_hist,
 180                      ractx->gain_rec, gain_window);
 181
 182     if (!compute_lpc_coefs(temp2, 10, ractx->gain_lpc, 0, 1, 1))
 183         apply_window(ractx->gain_lpc, ractx->gain_lpc, gain_bw_tab, 10);
 184 }
 185
 186 static int ra288_decode_frame(AVCodecContext * avctx, void *data,
 187                               int *data_size, const uint8_t * buf,
 188                               int buf_size)
 189 {
 190     int16_t *out = data;
 191     int i, j;
 192     RA288Context *ractx = avctx->priv_data;
 193     GetBitContext gb;
 194
 195     if (buf_size < avctx->block_align) {
 196         av_log(avctx, AV_LOG_ERROR,
 197                "Error! Input buffer is too small [%d<%d]\n",
 198                buf_size, avctx->block_align);
 199         return 0;
 200     }
 201
 202     if (*data_size < 32*5*2)
 203         return -1;
 204
 205     init_get_bits(&gb, buf, avctx->block_align * 8);
 206
 207     for (i=0; i < 32; i++) {
 208         float gain = amptable[get_bits(&gb, 3)];
 209         int cb_coef = get_bits(&gb, 6 + (i&1));
 210
 211         decode(ractx, gain, cb_coef);
 212
 213         for (j=0; j < 5; j++)
 214             *(out++) = 8 * ractx->sp_block[36 + j];
 215
 216         if ((i & 7) == 3)
 217             backward_filter(ractx);
 218     }
 219
 220     *data_size = (char *)out - (char *)data;
 221     return avctx->block_align;
 222 }
 223
 224 AVCodec ra_288_decoder =
 225 {
 226     "real_288",
 227     CODEC_TYPE_AUDIO,
 228     CODEC_ID_RA_288,
 229     sizeof(RA288Context),
 230     ra288_decode_init,
 231     NULL,
 232     NULL,
 233     ra288_decode_frame,
 234     .long_name = NULL_IF_CONFIG_SMALL("RealAudio 2.0 (28.8K)"),
 235 };