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adx.c
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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 
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 }
int ff_adx_decode_header(AVCodecContext *avctx, const uint8_t *buf, int bufsize, int *header_size, int *coeff)
Decode ADX stream header.
Definition: adx.c:38
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:59
const char * b
Definition: vf_curves.c:109
#define BLOCK_SIZE
Definition: adx.h:53
uint64_t_TMPL AV_WL64 unsigned int_TMPL AV_WL32 unsigned int_TMPL AV_WL24 unsigned int_TMPL AV_WL16 uint64_t_TMPL AV_WB64 unsigned int_TMPL AV_WB32 unsigned int_TMPL AV_WB24 unsigned int_TMPL AV_RB16
Definition: bytestream.h:85
void ff_adx_calculate_coeffs(int cutoff, int sample_rate, int bits, int *coeff)
Calculate LPC coefficients based on cutoff frequency and sample rate.
Definition: adx.c:26
void void avpriv_request_sample(void *avc, const char *msg,...) av_printf_format(2
Log a generic warning message about a missing feature.
uint8_t bits
Definition: crc.c:295
uint8_t
uint64_t_TMPL AV_WL64 unsigned int_TMPL AV_WL32 unsigned int_TMPL AV_WL24 unsigned int_TMPL AV_WL16 uint64_t_TMPL AV_WB64 unsigned int_TMPL AV_RB32
Definition: bytestream.h:85
#define lrintf(x)
Definition: libm_mips.h:70
#define COEFF_BITS
Definition: adx.h:51
static const uint8_t offset[127][2]
Definition: vf_spp.c:92
int bit_rate
the average bitrate
Definition: avcodec.h:1316
#define AVERROR_PATCHWELCOME
Not yet implemented in FFmpeg, patches welcome.
Definition: error.h:62
#define BLOCK_SAMPLES
Definition: adx.h:54
sample_rate
int sample_rate
samples per second
Definition: avcodec.h:2012
main external API structure.
Definition: avcodec.h:1252
void * buf
Definition: avisynth_c.h:553
#define M_SQRT2
Definition: mathematics.h:55
common internal and external API header
static double c[64]
int channels
number of audio channels
Definition: avcodec.h:2013
static const double coeff[2][5]
Definition: vf_owdenoise.c:71
#define M_PI
Definition: mathematics.h:46
SEGA CRI adx codecs.