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