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90 lines
3.7 KiB
C
90 lines
3.7 KiB
C
/*
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mpeghead: the bits of an MPEG frame header
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copyright ?-2011 by the mpg123 project - free software under the terms of the LGPL 2.1
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see COPYING and AUTHORS files in distribution or http://mpg123.org
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initially written by Michael Hipp & Thomas Orgis (from parse.c)
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*/
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#ifndef MPG123_MPEGHEAD_H
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#define MPG123_MPEGHEAD_H
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/*
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Avoid human error, let perl do the work of dissecting an MPEG header into parts.
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To be clear: Never edit the following definitions by hand, modify the code block inside this comment and run it through perl instead!
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$head = "AAAAAAAA AAABBCCD EEEEFFGH IIJJKLMM";
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%parts = qw(A sync B version C layer D crc E bitrate F samplerate G padding H private I channel J chanex K copyright L original M emphasis);
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for(sort keys %parts)
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{
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$name = uc($parts{$_});
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$bits = $head;
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$bits =~ s/$_/1/g;
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$bits =~ s/[^1 ]/0/g;
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print "\/\* $bits \*\/\n";
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$bits =~ s/\s//g;
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print "#define HDR_$name".(" " x (18-length($name))).sprintf("0x%08x", eval("0b$bits"))."\n";
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$bits =~ m/(0*)$/;
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print "#define HDR_${name}_VAL(h)".(" " x (11-length($name)))."(((h)\&HDR_$name) >> ".length($1).")\n";
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}
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*/
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/* 11111111 11100000 00000000 00000000 */
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#define HDR_SYNC 0xffe00000
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#define HDR_SYNC_VAL(h) (((h)&HDR_SYNC) >> 21)
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/* 00000000 00011000 00000000 00000000 */
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#define HDR_VERSION 0x00180000
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#define HDR_VERSION_VAL(h) (((h)&HDR_VERSION) >> 19)
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/* 00000000 00000110 00000000 00000000 */
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#define HDR_LAYER 0x00060000
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#define HDR_LAYER_VAL(h) (((h)&HDR_LAYER) >> 17)
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/* 00000000 00000001 00000000 00000000 */
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#define HDR_CRC 0x00010000
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#define HDR_CRC_VAL(h) (((h)&HDR_CRC) >> 16)
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/* 00000000 00000000 11110000 00000000 */
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#define HDR_BITRATE 0x0000f000
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#define HDR_BITRATE_VAL(h) (((h)&HDR_BITRATE) >> 12)
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/* 00000000 00000000 00001100 00000000 */
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#define HDR_SAMPLERATE 0x00000c00
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#define HDR_SAMPLERATE_VAL(h) (((h)&HDR_SAMPLERATE) >> 10)
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/* 00000000 00000000 00000010 00000000 */
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#define HDR_PADDING 0x00000200
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#define HDR_PADDING_VAL(h) (((h)&HDR_PADDING) >> 9)
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/* 00000000 00000000 00000001 00000000 */
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#define HDR_PRIVATE 0x00000100
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#define HDR_PRIVATE_VAL(h) (((h)&HDR_PRIVATE) >> 8)
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/* 00000000 00000000 00000000 11000000 */
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#define HDR_CHANNEL 0x000000c0
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#define HDR_CHANNEL_VAL(h) (((h)&HDR_CHANNEL) >> 6)
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/* 00000000 00000000 00000000 00110000 */
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#define HDR_CHANEX 0x00000030
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#define HDR_CHANEX_VAL(h) (((h)&HDR_CHANEX) >> 4)
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/* 00000000 00000000 00000000 00001000 */
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#define HDR_COPYRIGHT 0x00000008
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#define HDR_COPYRIGHT_VAL(h) (((h)&HDR_COPYRIGHT) >> 3)
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/* 00000000 00000000 00000000 00000100 */
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#define HDR_ORIGINAL 0x00000004
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#define HDR_ORIGINAL_VAL(h) (((h)&HDR_ORIGINAL) >> 2)
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/* 00000000 00000000 00000000 00000011 */
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#define HDR_EMPHASIS 0x00000003
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#define HDR_EMPHASIS_VAL(h) (((h)&HDR_EMPHASIS) >> 0)
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/*
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A generic mask for telling if a header is somewhat valid for the current stream.
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Meaning: Most basic info is not allowed to change.
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Checking of channel count needs to be done, too, though. So,
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if channel count matches, frames are decoded the same way: frame buffers and decoding
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routines can stay the same, especially frame buffers (think spf * channels!).
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*/
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#define HDR_CMPMASK (HDR_SYNC|HDR_VERSION|HDR_LAYER|HDR_SAMPLERATE)
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/* A stricter mask, for matching free format headers. */
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#define HDR_SAMEMASK (HDR_SYNC|HDR_VERSION|HDR_LAYER|HDR_BITRATE|HDR_SAMPLERATE|HDR_CHANNEL|HDR_CHANEX)
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/* Free format headers have zero bitrate value. */
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#define HDR_FREE_FORMAT(head) (!(head & HDR_BITRATE))
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/* A mask for changed sampling rate (version or rate bits). */
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#define HDR_SAMPMASK (HDR_VERSION|HDR_SAMPLERATE)
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#endif
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