110 lines
2.8 KiB
C
110 lines
2.8 KiB
C
#ifndef _mp3_header_h_
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#define _mp3_header_h_
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// https://en.wikipedia.org/wiki/MP3
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#if defined(__cplusplus)
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extern "C" {
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#endif
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/*
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ISO/IEC 11172-3
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2.4.1.3 Header
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unsigned int sync: 12
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unsigned int version: 1
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unsigned int layer: 2
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unsigned int error protection: 1
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unsigned int bitrate_index: 4
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unsigned int sampling_frequency: 2
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unsigned int padding: 1
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unsigned int private: 1
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unsigned int mode: 2
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unsigned int mode extension: 2
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unsigned int copyright: 1
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unsigned int original: 1
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unsigned int emphasis: 2
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bit_rate_index Layer I Layer II Layer III
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'0000' free format free format free format
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'0001' 32 kbit/s 32 kbit/s 32 kbit/s
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'0010' 64 kbit/s 48 kbit/s 40 kbit/s
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'0011' 96 kbit/s 56 kbit/s 48 kbit/s
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'0100' 128 kbit/s 64 kbit/s 56 kbit/s
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'0101' 160 kbit/s 80 kbit/s 64 kbit/s
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'0110' 192 kbit/s 96 kbit/s 80 kbit/s
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'0111' 224 kbit/s 112 kbit/s 96 kbit/s
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'1000' 256 kbit/s 128 kbit/s 112 kbit/s
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'1001' 288 kbit/s 160 kbit/s 128 kbit/s
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'1010' 320 kbit/s 192 kbit/s 160 kbit/s
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'1011' 352 kbit/s 224 kbit/s 192 kbit/s
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'1100' 384 kbit/s 256 kbit/s 224 kbit/s
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'1101' 416 kbit/s 320 kbit/s 256 kbit/s
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'1110' 448 kbit/s 384 kbit/s 320 kbit/s
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sampling_frequency
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'00' 44.1 kHz
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'01' 48 kHz
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'10' 32 kHz
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'11' reserved
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mode
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'00' stereo
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'01' joint_stereo (intensity_stereo and/or ms_stereo)
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'10' dual_channel
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'11' single_channel
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mode_extension
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'00' subbands 4-31 in intensity_stereo, bound==4
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'01' subbands 8-31 in intensity_stereo, bound==8
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'10' subbands 12-31 in intensity_stereo, bound==12
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'11' subbands 16-31 in intensity_stereo, bound==16
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emphasis
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'00' no emphasis
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'01' 50/15 microsec. emphasis
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'10' reserved
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'11' CCITT J.17
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*/
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struct mp3_header_t
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{
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unsigned int version : 2; // 0-MPEG 2.5, 1-undefined, 2-MPEG-2, 3-MPEG-1
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unsigned int layer : 2; // 3-Layer I, 2-Layer II, 1-Layer III, 0-reserved
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unsigned int protection : 1;
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unsigned int bitrate_index : 4; //0-free,
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unsigned int sampling_frequency : 2;
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unsigned int priviate : 1;
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unsigned int mode : 2;
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unsigned int mode_extension : 2;
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unsigned int copyright : 1;
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unsigned int original : 1;
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unsigned int emphasis : 2;
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};
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// version
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#define MP3_MPEG1 3
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#define MP3_MPEG2 2
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#define MP3_MPEG2_5 0
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// layer
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#define MP3_LAYER1 3
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#define MP3_LAYER2 2
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#define MP3_LAYER3 1
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#define MP3_BITS_PER_SAMPLE 16
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///MP3 Header size: 4
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int mp3_header_load(struct mp3_header_t* mp3, const void* data, int bytes);
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int mp3_header_save(const struct mp3_header_t* mp3, void* data, int bytes);
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int mp3_get_channel(const struct mp3_header_t* mp3);
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int mp3_get_bitrate(const struct mp3_header_t* mp3);
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int mp3_set_bitrate(struct mp3_header_t* mp3, int bitrate);
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int mp3_get_frequency(const struct mp3_header_t* mp3);
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int mp3_set_frequency(struct mp3_header_t* mp3, int frequency);
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#if defined(__cplusplus)
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}
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#endif
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#endif /* !_mp3_header_h_ */
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