1/* 2 * Copyright (c) 2011 Justin Ruggles 3 * 4 * This file is part of Libav. 5 * 6 * Libav 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 * Libav 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 Libav; 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/intreadwrite.h" 22#include "libavutil/mathematics.h" 23#include "adx.h" 24 25void ff_adx_calculate_coeffs(int cutoff, int sample_rate, int bits, int *coeff) 26{ 27 double a, b, c; 28 29 a = M_SQRT2 - cos(2.0 * M_PI * cutoff / sample_rate); 30 b = M_SQRT2 - 1.0; 31 c = (a - sqrt((a + b) * (a - b))) / b; 32 33 coeff[0] = lrintf(c * 2.0 * (1 << bits)); 34 coeff[1] = lrintf(-(c * c) * (1 << bits)); 35} 36 37int avpriv_adx_decode_header(AVCodecContext *avctx, const uint8_t *buf, 38 int bufsize, int *header_size, int *coeff) 39{ 40 int offset, cutoff; 41 42 if (bufsize < 24) 43 return AVERROR_INVALIDDATA; 44 45 if (AV_RB16(buf) != 0x8000) 46 return AVERROR_INVALIDDATA; 47 offset = AV_RB16(buf + 2) + 4; 48 49 /* if copyright string is within the provided data, validate it */ 50 if (bufsize >= offset && memcmp(buf + offset - 6, "(c)CRI", 6)) 51 return AVERROR_INVALIDDATA; 52 53 /* check for encoding=3 block_size=18, sample_size=4 */ 54 if (buf[4] != 3 || buf[5] != 18 || buf[6] != 4) { 55 av_log_ask_for_sample(avctx, "unsupported ADX format\n"); 56 return AVERROR_PATCHWELCOME; 57 } 58 59 /* channels */ 60 avctx->channels = buf[7]; 61 if (avctx->channels <= 0 || avctx->channels > 2) 62 return AVERROR_INVALIDDATA; 63 64 /* sample rate */ 65 avctx->sample_rate = AV_RB32(buf + 8); 66 if (avctx->sample_rate < 1 || 67 avctx->sample_rate > INT_MAX / (avctx->channels * BLOCK_SIZE * 8)) 68 return AVERROR_INVALIDDATA; 69 70 /* bit rate */ 71 avctx->bit_rate = avctx->sample_rate * avctx->channels * BLOCK_SIZE * 8 / BLOCK_SAMPLES; 72 73 /* LPC coefficients */ 74 if (coeff) { 75 cutoff = AV_RB16(buf + 16); 76 ff_adx_calculate_coeffs(cutoff, avctx->sample_rate, COEFF_BITS, coeff); 77 } 78 79 *header_size = offset; 80 return 0; 81} 82