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libavcodec
adx.c
Go to the documentation of this file.
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/*
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* Copyright (c) 2011 Justin Ruggles
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*
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* This file is part of Libav.
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*
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* Libav is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* Libav is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with Libav; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "
libavutil/intreadwrite.h
"
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#include "
libavutil/mathematics.h
"
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#include "
adx.h
"
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void
ff_adx_calculate_coeffs
(
int
cutoff,
int
sample_rate,
int
bits
,
int
*coeff)
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{
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double
a,
b
, c;
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a =
M_SQRT2
- cos(2.0 *
M_PI
* cutoff / sample_rate);
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b =
M_SQRT2
- 1.0;
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c = (a - sqrt((a + b) * (a - b))) / b;
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coeff[0] =
lrintf
(c * 2.0 * (1 << bits));
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coeff[1] =
lrintf
(-(c * c) * (1 << bits));
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}
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int
avpriv_adx_decode_header
(
AVCodecContext
*avctx,
const
uint8_t *buf,
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int
bufsize,
int
*header_size,
int
*coeff)
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{
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int
offset, cutoff;
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if
(bufsize < 24)
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return
AVERROR_INVALIDDATA
;
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if
(
AV_RB16
(buf) != 0x8000)
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return
AVERROR_INVALIDDATA
;
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offset =
AV_RB16
(buf + 2) + 4;
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/* if copyright string is within the provided data, validate it */
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if
(bufsize >= offset && offset >= 6 && memcmp(buf + offset - 6,
"(c)CRI"
, 6))
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return
AVERROR_INVALIDDATA
;
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/* check for encoding=3 block_size=18, sample_size=4 */
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if
(buf[4] != 3 || buf[5] != 18 || buf[6] != 4) {
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av_log_ask_for_sample
(avctx,
"unsupported ADX format\n"
);
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return
AVERROR_PATCHWELCOME
;
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}
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/* channels */
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avctx->
channels
= buf[7];
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if
(avctx->
channels
<= 0 || avctx->
channels
> 2)
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return
AVERROR_INVALIDDATA
;
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/* sample rate */
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avctx->
sample_rate
=
AV_RB32
(buf + 8);
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if
(avctx->
sample_rate
< 1 ||
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avctx->
sample_rate
> INT_MAX / (avctx->
channels
*
BLOCK_SIZE
* 8))
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return
AVERROR_INVALIDDATA
;
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/* bit rate */
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avctx->
bit_rate
= avctx->
sample_rate
* avctx->
channels
*
BLOCK_SIZE
* 8 /
BLOCK_SAMPLES
;
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/* LPC coefficients */
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if
(coeff) {
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cutoff =
AV_RB16
(buf + 16);
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ff_adx_calculate_coeffs
(cutoff, avctx->
sample_rate
,
COEFF_BITS
, coeff);
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}
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*header_size = offset;
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return
0;
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}