2 * Copyright (c) 2011 Justin Ruggles
4 * This file is part of FFmpeg.
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.
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.
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
21 #include "libavutil/common.h"
22 #include "libavutil/intreadwrite.h"
23 #include "libavutil/mathematics.h"
26 void ff_adx_calculate_coeffs(int cutoff
, int sample_rate
, int bits
, int *coeff
)
30 a
= M_SQRT2
- cos(2.0 * M_PI
* cutoff
/ sample_rate
);
32 c
= (a
- sqrt((a
+ b
) * (a
- b
))) / b
;
34 coeff
[0] = lrintf(c
* 2.0 * (1 << bits
));
35 coeff
[1] = lrintf(-(c
* c
) * (1 << bits
));
38 int ff_adx_decode_header(AVCodecContext
*avctx
, const uint8_t *buf
,
39 int bufsize
, int *header_size
, int *coeff
)
44 return AVERROR_INVALIDDATA
;
46 if (AV_RB16(buf
) != 0x8000)
47 return AVERROR_INVALIDDATA
;
48 offset
= AV_RB16(buf
+ 2) + 4;
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
;
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
;
61 avctx
->channels
= buf
[7];
62 if (avctx
->channels
<= 0 || avctx
->channels
> 2)
63 return AVERROR_INVALIDDATA
;
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
;
72 avctx
->bit_rate
= avctx
->sample_rate
* avctx
->channels
* BLOCK_SIZE
* 8 / BLOCK_SAMPLES
;
74 /* LPC coefficients */
76 cutoff
= AV_RB16(buf
+ 16);
77 ff_adx_calculate_coeffs(cutoff
, avctx
->sample_rate
, COEFF_BITS
, coeff
);
80 *header_size
= offset
;