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77 lines
2.3 KiB
C
77 lines
2.3 KiB
C
/*
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* MPEG Audio header decoder
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* Copyright (c) 2001, 2002 Fabrice Bellard
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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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/**
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* @file
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* MPEG Audio header decoder.
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*/
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#ifndef AVCODEC_MPEGAUDIODECHEADER_H
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#define AVCODEC_MPEGAUDIODECHEADER_H
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#include "avcodec.h"
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#define MP3_MASK 0xFFFE0CCF
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#define MPA_DECODE_HEADER \
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int frame_size; \
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int error_protection; \
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int layer; \
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int sample_rate; \
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int sample_rate_index; /* between 0 and 8 */ \
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int bit_rate; \
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int nb_channels; \
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int mode; \
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int mode_ext; \
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int lsf;
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typedef struct MPADecodeHeader {
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MPA_DECODE_HEADER
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} MPADecodeHeader;
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/* header decoding. MUST check the header before because no
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consistency check is done there. Return 1 if free format found and
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that the frame size must be computed externally */
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int ff_mpegaudio_decode_header(MPADecodeHeader *s, uint32_t header);
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/* useful helper to get mpeg audio stream infos. Return -1 if error in
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header, otherwise the coded frame size in bytes */
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int ff_mpa_decode_header(AVCodecContext *avctx, uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bitrate);
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/* fast header check for resync */
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static inline int ff_mpa_check_header(uint32_t header){
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/* header */
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if ((header & 0xffe00000) != 0xffe00000)
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return -1;
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/* layer check */
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if ((header & (3<<17)) == 0)
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return -1;
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/* bit rate */
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if ((header & (0xf<<12)) == 0xf<<12)
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return -1;
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/* frequency */
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if ((header & (3<<10)) == 3<<10)
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return -1;
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return 0;
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}
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#endif /* AVCODEC_MPEGAUDIODECHEADER_H */
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