blob: cd88b16660886f5dba66adcf5004653c8deb3470
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 | } |
83 |