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
ff_adx_calculate_coeffs(int cutoff,int sample_rate,int bits,int * coeff)26 void 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
ff_adx_decode_header(AVCodecContext * avctx,const uint8_t * buf,int bufsize,int * header_size,int * coeff)38 int 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