| 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 | |
| 26 | void 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 | |
| 38 | int 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 | } |