/*

mpeghead: the bits of an MPEG frame header

copyright ?-2011 by the mpg123 project - free software under the terms of the LGPL 2.1

see COPYING and AUTHORS files in distribution or http://mpg123.org

initially written by Michael Hipp & Thomas Orgis (from parse.c)

*/

#ifndef MPG123_MPEGHEAD_H

#define MPG123_MPEGHEAD_H

/*

Avoid human error, let perl do the work of dissecting an MPEG header into parts.

To be clear: Never edit the following definitions by hand, modify the code block inside this comment and run it through perl instead!

$head = "AAAAAAAA AAABBCCD EEEEFFGH IIJJKLMM";

%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);

for(sort keys %parts)

{

$name = uc($parts{$_});

$bits = $head;

$bits =~ s/$_/1/g;

$bits =~ s/[^1 ]/0/g;

print "\/\* $bits \*\/\n";

$bits =~ s/\s//g;

print "#define HDR_$name".(" " x (18-length($name))).sprintf("0x%08x", eval("0b$bits"))."\n";

$bits =~ m/(0*)$/;

print "#define HDR_${name}_VAL(h)".(" " x (11-length($name)))."(((h)\&HDR_$name) >> ".length($1).")\n";

}

*/

/* 11111111 11100000 00000000 00000000 */

#define HDR_SYNC 0xffe00000

#define HDR_SYNC_VAL(h) (((h)&HDR_SYNC) >> 21)

/* 00000000 00011000 00000000 00000000 */

#define HDR_VERSION 0x00180000

#define HDR_VERSION_VAL(h) (((h)&HDR_VERSION) >> 19)

/* 00000000 00000110 00000000 00000000 */

#define HDR_LAYER 0x00060000

#define HDR_LAYER_VAL(h) (((h)&HDR_LAYER) >> 17)

/* 00000000 00000001 00000000 00000000 */

#define HDR_CRC 0x00010000

#define HDR_CRC_VAL(h) (((h)&HDR_CRC) >> 16)

/* 00000000 00000000 11110000 00000000 */

#define HDR_BITRATE 0x0000f000

#define HDR_BITRATE_VAL(h) (((h)&HDR_BITRATE) >> 12)

/* 00000000 00000000 00001100 00000000 */

#define HDR_SAMPLERATE 0x00000c00

#define HDR_SAMPLERATE_VAL(h) (((h)&HDR_SAMPLERATE) >> 10)

/* 00000000 00000000 00000010 00000000 */

#define HDR_PADDING 0x00000200

#define HDR_PADDING_VAL(h) (((h)&HDR_PADDING) >> 9)

/* 00000000 00000000 00000001 00000000 */

#define HDR_PRIVATE 0x00000100

#define HDR_PRIVATE_VAL(h) (((h)&HDR_PRIVATE) >> 8)

/* 00000000 00000000 00000000 11000000 */

#define HDR_CHANNEL 0x000000c0

#define HDR_CHANNEL_VAL(h) (((h)&HDR_CHANNEL) >> 6)

/* 00000000 00000000 00000000 00110000 */

#define HDR_CHANEX 0x00000030

#define HDR_CHANEX_VAL(h) (((h)&HDR_CHANEX) >> 4)

/* 00000000 00000000 00000000 00001000 */

#define HDR_COPYRIGHT 0x00000008

#define HDR_COPYRIGHT_VAL(h) (((h)&HDR_COPYRIGHT) >> 3)

/* 00000000 00000000 00000000 00000100 */

#define HDR_ORIGINAL 0x00000004

#define HDR_ORIGINAL_VAL(h) (((h)&HDR_ORIGINAL) >> 2)

/* 00000000 00000000 00000000 00000011 */

#define HDR_EMPHASIS 0x00000003

#define HDR_EMPHASIS_VAL(h) (((h)&HDR_EMPHASIS) >> 0)

/*

A generic mask for telling if a header is somewhat valid for the current stream.

Meaning: Most basic info is not allowed to change.

Checking of channel count needs to be done, too, though. So,

if channel count matches, frames are decoded the same way: frame buffers and decoding

routines can stay the same, especially frame buffers (think spf * channels!).

*/

#define HDR_CMPMASK (HDR_SYNC|HDR_VERSION|HDR_LAYER|HDR_SAMPLERATE)

/* A stricter mask, for matching free format headers. */

/* Free format headers have zero bitrate value. */

#define HDR_FREE_FORMAT(head) (!(head & HDR_BITRATE))

/* A mask for changed sampling rate (version or rate bits). */

#define HDR_SAMPMASK (HDR_VERSION|HDR_SAMPLERATE)

#endif