1/*
2 * Copyright (c) 2011  Justin Ruggles
3 *
4 * This file is part of FFmpeg.
5 *
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * FFmpeg is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
21#include "libavutil/common.h"
22#include "libavutil/intreadwrite.h"
23#include "libavutil/mathematics.h"
24#include "adx.h"
25
26void ff_adx_calculate_coeffs(int cutoff, int sample_rate, int bits, int *coeff)
27{
28    double a, b, c;
29
30    a = M_SQRT2 - cos(2.0 * M_PI * cutoff / sample_rate);
31    b = M_SQRT2 - 1.0;
32    c = (a - sqrt((a + b) * (a - b))) / b;
33
34    coeff[0] = lrintf(c * 2.0  * (1 << bits));
35    coeff[1] = lrintf(-(c * c) * (1 << bits));
36}
37
38int ff_adx_decode_header(AVCodecContext *avctx, const uint8_t *buf,
39                         int bufsize, int *header_size, int *coeff)
40{
41    int offset, cutoff;
42
43    if (bufsize < 24)
44        return AVERROR_INVALIDDATA;
45
46    if (AV_RB16(buf) != 0x8000)
47        return AVERROR_INVALIDDATA;
48    offset = AV_RB16(buf + 2) + 4;
49
50    /* if copyright string is within the provided data, validate it */
51    if (bufsize >= offset && offset >= 6 && memcmp(buf + offset - 6, "(c)CRI", 6))
52        return AVERROR_INVALIDDATA;
53
54    /* check for encoding=3 block_size=18, sample_size=4 */
55    if (buf[4] != 3 || buf[5] != 18 || buf[6] != 4) {
56        avpriv_request_sample(avctx, "Support for this ADX format");
57        return AVERROR_PATCHWELCOME;
58    }
59
60    /* channels */
61    avctx->channels = buf[7];
62    if (avctx->channels <= 0 || avctx->channels > 2)
63        return AVERROR_INVALIDDATA;
64
65    /* sample rate */
66    avctx->sample_rate = AV_RB32(buf + 8);
67    if (avctx->sample_rate < 1 ||
68        avctx->sample_rate > INT_MAX / (avctx->channels * BLOCK_SIZE * 8))
69        return AVERROR_INVALIDDATA;
70
71    /* bit rate */
72    avctx->bit_rate = avctx->sample_rate * avctx->channels * BLOCK_SIZE * 8 / BLOCK_SAMPLES;
73
74    /* LPC coefficients */
75    if (coeff) {
76        cutoff = AV_RB16(buf + 16);
77        ff_adx_calculate_coeffs(cutoff, avctx->sample_rate, COEFF_BITS, coeff);
78    }
79
80    *header_size = offset;
81    return 0;
82}
83
84#if LIBAVCODEC_VERSION_MAJOR < 56
85int avpriv_adx_decode_header(AVCodecContext *avctx, const uint8_t *buf,
86                             int bufsize, int *header_size, int *coeff)
87{
88    return ff_adx_decode_header(avctx, buf, bufsize, header_size, coeff);
89}
90#endif
91