1/*
2 * Real Audio 1.0 (14.4K)
3 *
4 * Copyright (c) 2008 Vitor Sessak
5 * Copyright (c) 2003 Nick Kurshev
6 *     Based on public domain decoder at http://www.honeypot.net/audio
7 *
8 * This file is part of FFmpeg.
9 *
10 * FFmpeg is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU Lesser General Public
12 * License as published by the Free Software Foundation; either
13 * version 2.1 of the License, or (at your option) any later version.
14 *
15 * FFmpeg is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
18 * Lesser General Public License for more details.
19 *
20 * You should have received a copy of the GNU Lesser General Public
21 * License along with FFmpeg; if not, write to the Free Software
22 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23 */
24
25#include "libavutil/intmath.h"
26#include "avcodec.h"
27#include "get_bits.h"
28#include "ra144.h"
29#include "celp_filters.h"
30
31#define NBLOCKS         4       ///< number of subblocks within a block
32#define BLOCKSIZE       40      ///< subblock size in 16-bit words
33#define BUFFERSIZE      146     ///< the size of the adaptive codebook
34
35
36typedef struct {
37    AVCodecContext *avctx;
38
39    unsigned int     old_energy;        ///< previous frame energy
40
41    unsigned int     lpc_tables[2][10];
42
43    /** LPC coefficients: lpc_coef[0] is the coefficients of the current frame
44     *  and lpc_coef[1] of the previous one. */
45    unsigned int    *lpc_coef[2];
46
47    unsigned int     lpc_refl_rms[2];
48
49    /** The current subblock padded by the last 10 values of the previous one. */
50    int16_t curr_sblock[50];
51
52    /** Adaptive codebook, its size is two units bigger to avoid a
53     *  buffer overflow. */
54    uint16_t adapt_cb[146+2];
55} RA144Context;
56
57static av_cold int ra144_decode_init(AVCodecContext * avctx)
58{
59    RA144Context *ractx = avctx->priv_data;
60
61    ractx->avctx = avctx;
62
63    ractx->lpc_coef[0] = ractx->lpc_tables[0];
64    ractx->lpc_coef[1] = ractx->lpc_tables[1];
65
66    avctx->sample_fmt = SAMPLE_FMT_S16;
67    return 0;
68}
69
70/**
71 * Evaluate sqrt(x << 24). x must fit in 20 bits. This value is evaluated in an
72 * odd way to make the output identical to the binary decoder.
73 */
74static int t_sqrt(unsigned int x)
75{
76    int s = 2;
77    while (x > 0xfff) {
78        s++;
79        x >>= 2;
80    }
81
82    return ff_sqrt(x << 20) << s;
83}
84
85/**
86 * Evaluate the LPC filter coefficients from the reflection coefficients.
87 * Does the inverse of the eval_refl() function.
88 */
89static void eval_coefs(int *coefs, const int *refl)
90{
91    int buffer[10];
92    int *b1 = buffer;
93    int *b2 = coefs;
94    int i, j;
95
96    for (i=0; i < 10; i++) {
97        b1[i] = refl[i] << 4;
98
99        for (j=0; j < i; j++)
100            b1[j] = ((refl[i] * b2[i-j-1]) >> 12) + b2[j];
101
102        FFSWAP(int *, b1, b2);
103    }
104
105    for (i=0; i < 10; i++)
106        coefs[i] >>= 4;
107}
108
109/**
110 * Copy the last offset values of *source to *target. If those values are not
111 * enough to fill the target buffer, fill it with another copy of those values.
112 */
113static void copy_and_dup(int16_t *target, const int16_t *source, int offset)
114{
115    source += BUFFERSIZE - offset;
116
117    memcpy(target, source, FFMIN(BLOCKSIZE, offset)*sizeof(*target));
118    if (offset < BLOCKSIZE)
119        memcpy(target + offset, source, (BLOCKSIZE - offset)*sizeof(*target));
120}
121
122/** inverse root mean square */
123static int irms(const int16_t *data)
124{
125    unsigned int i, sum = 0;
126
127    for (i=0; i < BLOCKSIZE; i++)
128        sum += data[i] * data[i];
129
130    if (sum == 0)
131        return 0; /* OOPS - division by zero */
132
133    return 0x20000000 / (t_sqrt(sum) >> 8);
134}
135
136static void add_wav(int16_t *dest, int n, int skip_first, int *m,
137                    const int16_t *s1, const int8_t *s2, const int8_t *s3)
138{
139    int i;
140    int v[3];
141
142    v[0] = 0;
143    for (i=!skip_first; i<3; i++)
144        v[i] = (gain_val_tab[n][i] * m[i]) >> gain_exp_tab[n];
145
146    if (v[0]) {
147        for (i=0; i < BLOCKSIZE; i++)
148            dest[i] = (s1[i]*v[0] + s2[i]*v[1] + s3[i]*v[2]) >> 12;
149    } else {
150        for (i=0; i < BLOCKSIZE; i++)
151            dest[i] = (             s2[i]*v[1] + s3[i]*v[2]) >> 12;
152    }
153}
154
155static unsigned int rescale_rms(unsigned int rms, unsigned int energy)
156{
157    return (rms * energy) >> 10;
158}
159
160static unsigned int rms(const int *data)
161{
162    int i;
163    unsigned int res = 0x10000;
164    int b = 10;
165
166    for (i=0; i < 10; i++) {
167        res = (((0x1000000 - data[i]*data[i]) >> 12) * res) >> 12;
168
169        if (res == 0)
170            return 0;
171
172        while (res <= 0x3fff) {
173            b++;
174            res <<= 2;
175        }
176    }
177
178    return t_sqrt(res) >> b;
179}
180
181static void do_output_subblock(RA144Context *ractx, const uint16_t  *lpc_coefs,
182                               int gval, GetBitContext *gb)
183{
184    uint16_t buffer_a[40];
185    uint16_t *block;
186    int cba_idx = get_bits(gb, 7); // index of the adaptive CB, 0 if none
187    int gain    = get_bits(gb, 8);
188    int cb1_idx = get_bits(gb, 7);
189    int cb2_idx = get_bits(gb, 7);
190    int m[3];
191
192    if (cba_idx) {
193        cba_idx += BLOCKSIZE/2 - 1;
194        copy_and_dup(buffer_a, ractx->adapt_cb, cba_idx);
195        m[0] = (irms(buffer_a) * gval) >> 12;
196    } else {
197        m[0] = 0;
198    }
199
200    m[1] = (cb1_base[cb1_idx] * gval) >> 8;
201    m[2] = (cb2_base[cb2_idx] * gval) >> 8;
202
203    memmove(ractx->adapt_cb, ractx->adapt_cb + BLOCKSIZE,
204            (BUFFERSIZE - BLOCKSIZE) * sizeof(*ractx->adapt_cb));
205
206    block = ractx->adapt_cb + BUFFERSIZE - BLOCKSIZE;
207
208    add_wav(block, gain, cba_idx, m, cba_idx? buffer_a: NULL,
209            cb1_vects[cb1_idx], cb2_vects[cb2_idx]);
210
211    memcpy(ractx->curr_sblock, ractx->curr_sblock + 40,
212           10*sizeof(*ractx->curr_sblock));
213
214    if (ff_celp_lp_synthesis_filter(ractx->curr_sblock + 10, lpc_coefs,
215                                    block, BLOCKSIZE, 10, 1, 0xfff))
216        memset(ractx->curr_sblock, 0, 50*sizeof(*ractx->curr_sblock));
217}
218
219static void int_to_int16(int16_t *out, const int *inp)
220{
221    int i;
222
223    for (i=0; i < 10; i++)
224        *out++ = *inp++;
225}
226
227/**
228 * Evaluate the reflection coefficients from the filter coefficients.
229 * Does the inverse of the eval_coefs() function.
230 *
231 * @return 1 if one of the reflection coefficients is greater than
232 *         4095, 0 if not.
233 */
234static int eval_refl(int *refl, const int16_t *coefs, AVCodecContext *avctx)
235{
236    int b, i, j;
237    int buffer1[10];
238    int buffer2[10];
239    int *bp1 = buffer1;
240    int *bp2 = buffer2;
241
242    for (i=0; i < 10; i++)
243        buffer2[i] = coefs[i];
244
245    refl[9] = bp2[9];
246
247    if ((unsigned) bp2[9] + 0x1000 > 0x1fff) {
248        av_log(avctx, AV_LOG_ERROR, "Overflow. Broken sample?\n");
249        return 1;
250    }
251
252    for (i=8; i >= 0; i--) {
253        b = 0x1000-((bp2[i+1] * bp2[i+1]) >> 12);
254
255        if (!b)
256            b = -2;
257
258        for (j=0; j <= i; j++)
259            bp1[j] = ((bp2[j] - ((refl[i+1] * bp2[i-j]) >> 12)) * (0x1000000 / b)) >> 12;
260
261        if ((unsigned) bp1[i] + 0x1000 > 0x1fff)
262            return 1;
263
264        refl[i] = bp1[i];
265
266        FFSWAP(int *, bp1, bp2);
267    }
268    return 0;
269}
270
271static int interp(RA144Context *ractx, int16_t *out, int a,
272                  int copyold, int energy)
273{
274    int work[10];
275    int b = NBLOCKS - a;
276    int i;
277
278    // Interpolate block coefficients from the this frame's forth block and
279    // last frame's forth block.
280    for (i=0; i<10; i++)
281        out[i] = (a * ractx->lpc_coef[0][i] + b * ractx->lpc_coef[1][i])>> 2;
282
283    if (eval_refl(work, out, ractx->avctx)) {
284        // The interpolated coefficients are unstable, copy either new or old
285        // coefficients.
286        int_to_int16(out, ractx->lpc_coef[copyold]);
287        return rescale_rms(ractx->lpc_refl_rms[copyold], energy);
288    } else {
289        return rescale_rms(rms(work), energy);
290    }
291}
292
293/** Uncompress one block (20 bytes -> 160*2 bytes). */
294static int ra144_decode_frame(AVCodecContext * avctx, void *vdata,
295                              int *data_size, AVPacket *avpkt)
296{
297    const uint8_t *buf = avpkt->data;
298    int buf_size = avpkt->size;
299    static const uint8_t sizes[10] = {6, 5, 5, 4, 4, 3, 3, 3, 3, 2};
300    unsigned int refl_rms[4];    // RMS of the reflection coefficients
301    uint16_t block_coefs[4][10]; // LPC coefficients of each sub-block
302    unsigned int lpc_refl[10];   // LPC reflection coefficients of the frame
303    int i, j;
304    int16_t *data = vdata;
305    unsigned int energy;
306
307    RA144Context *ractx = avctx->priv_data;
308    GetBitContext gb;
309
310    if (*data_size < 2*160)
311        return -1;
312
313    if(buf_size < 20) {
314        av_log(avctx, AV_LOG_ERROR,
315               "Frame too small (%d bytes). Truncated file?\n", buf_size);
316        *data_size = 0;
317        return buf_size;
318    }
319    init_get_bits(&gb, buf, 20 * 8);
320
321    for (i=0; i<10; i++)
322        lpc_refl[i] = lpc_refl_cb[i][get_bits(&gb, sizes[i])];
323
324    eval_coefs(ractx->lpc_coef[0], lpc_refl);
325    ractx->lpc_refl_rms[0] = rms(lpc_refl);
326
327    energy = energy_tab[get_bits(&gb, 5)];
328
329    refl_rms[0] = interp(ractx, block_coefs[0], 1, 1, ractx->old_energy);
330    refl_rms[1] = interp(ractx, block_coefs[1], 2, energy <= ractx->old_energy,
331                    t_sqrt(energy*ractx->old_energy) >> 12);
332    refl_rms[2] = interp(ractx, block_coefs[2], 3, 0, energy);
333    refl_rms[3] = rescale_rms(ractx->lpc_refl_rms[0], energy);
334
335    int_to_int16(block_coefs[3], ractx->lpc_coef[0]);
336
337    for (i=0; i < 4; i++) {
338        do_output_subblock(ractx, block_coefs[i], refl_rms[i], &gb);
339
340        for (j=0; j < BLOCKSIZE; j++)
341            *data++ = av_clip_int16(ractx->curr_sblock[j + 10] << 2);
342    }
343
344    ractx->old_energy = energy;
345    ractx->lpc_refl_rms[1] = ractx->lpc_refl_rms[0];
346
347    FFSWAP(unsigned int *, ractx->lpc_coef[0], ractx->lpc_coef[1]);
348
349    *data_size = 2*160;
350    return 20;
351}
352
353AVCodec ra_144_decoder =
354{
355    "real_144",
356    AVMEDIA_TYPE_AUDIO,
357    CODEC_ID_RA_144,
358    sizeof(RA144Context),
359    ra144_decode_init,
360    NULL,
361    NULL,
362    ra144_decode_frame,
363    .long_name = NULL_IF_CONFIG_SMALL("RealAudio 1.0 (14.4K)"),
364};
365