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 26void 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 38int ff_adx_decode_header(AVCodecContext *avctx, const uint8_t *buf, 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} 83 84#if LIBAVCODEC_VERSION_MAJOR < 56 85int avpriv_adx_decode_header(AVCodecContext *avctx, const uint8_t *buf, 86 int bufsize, int *header_size, int *coeff) 87{ 88 return ff_adx_decode_header(avctx, buf, bufsize, header_size, coeff); 89} 90#endif 91