• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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