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81 lines
2.5 KiB
81 lines
2.5 KiB
/* |
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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 avpriv_mpegaudio_decode_header(MPADecodeHeader *s, uint32_t header); |
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/* useful helper to get MPEG audio stream info. 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, |
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int *channels, int *frame_size, int *bitrate); |
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#if LIBAVCODEC_VERSION_MAJOR < 57 |
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int avpriv_mpa_decode_header(AVCodecContext *avctx, uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bitrate); |
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#endif |
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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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