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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 | ||
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 | ||
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 | } |