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