| 0,0 → 1,87 |
|---|
| /* |
| * 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 avpriv_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 (offset < 6) { |
| av_log(avctx, AV_LOG_ERROR, "offset is prior data\n"); |
| return AVERROR_INVALIDDATA; |
| } |
| |
| /* if copyright string is within the provided data, validate it */ |
| if (bufsize >= offset && 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; |
| } |