# Copyright (C) 2005-2010 by Mandriva SA
#                            Pascal Rigaux
#                            Anssi Hannula
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

package Parse::EDID;

use strict;
use warnings;
use base 'Exporter';

our $VERSION = '1.0.2';

our @EXPORT = qw(
     parse_edid
     check_parsed_edid
     find_edid_in_string
);

my @CVT_ratios = qw(5/4 4/3 3/2 16/10 15/9 16/9);
my @known_ratios = @CVT_ratios;

my @edid_info = _group_by2(
    a8 => '_header',
    a2  => 'manufacturer_name',

    v => 'product_code',
    V => 'serial_number',
    C => 'week',
    C => 'year',
    C => 'edid_version',
    C => 'edid_revision',
    a => 'video_input_definition',

    C => 'max_size_horizontal', # in cm, 0 on projectors
    C => 'max_size_vertical', # in cm, 0 on projectors
    C => 'gamma',
    a => 'feature_support',
    a10 => '_color_characteristics',
    a3  => 'established_timings',
    a16 => 'standard_timings',
    a72 => 'monitor_details',

    C => 'extension_flag',
    C => 'checksum',
);

my %subfields = (
    manufacturer_name => [ _group_by2(
        1 => '',
        5 => '1',
        5 => '2',
        5 => '3',
    ) ],

    video_input_definition => [ _group_by2(
        1 => 'digital',
        1 => 'separate_sync',
        1 => 'composite_sync',
        1 => 'sync_on_green',
        2 => '',
        2 => 'voltage_level',
    ) ],

    feature_support => [ _group_by2(
        1 => 'DPMS_standby',
        1 => 'DPMS_suspend',
        1 => 'DPMS_active_off',        
        1 => 'rgb',

        1 => '',
        1 => 'sRGB_compliance',
        1 => 'has_preferred_timing',
        1 => 'GTF_compliance',
    ) ],

    established_timings => [ _group_by2(
        1 => '720x400_70',
        1 => '720x400_88',
        1 => '640x480_60',
        1 => '640x480_67',
        1 => '640x480_72',
        1 => '640x480_75',
        1 => '800x600_56',
        1 => '800x600_60',
        1 => '800x600_72',
        1 => '800x600_75',
        1 => '832x624_75',
        1 => '1024x768_87i',
        1 => '1024x768_60',
        1 => '1024x768_70',
        1 => '1024x768_75',
        1 => '1280x1024_75',
    ) ],

    detailed_timing => [ _group_by2(
        8 => 'horizontal_active',
        8 => 'horizontal_blanking',
        4 => 'horizontal_active_hi',
        4 => 'horizontal_blanking_hi',
        8 => 'vertical_active',
        8 => 'vertical_blanking',
        4 => 'vertical_active_hi',
        4 => 'vertical_blanking_hi',
        8 => 'horizontal_sync_offset',
        8 => 'horizontal_sync_pulse_width',
        4 => 'vertical_sync_offset',
        4 => 'vertical_sync_pulse_width',
        2 => 'horizontal_sync_offset_hi',
        2 => 'horizontal_sync_pulse_width_hi',
        2 => 'vertical_sync_offset_hi',
        2 => 'vertical_sync_pulse_width_hi',
        8 => 'horizontal_image_size', # in mm
        8 => 'vertical_image_size', # in mm
        4 => 'horizontal_image_size_hi',
        4 => 'vertical_image_size_hi',
        8 => 'horizontal_border',
        8 => 'vertical_border',

        1 => 'interlaced',
        2 => 'stereo',      
        2 => 'digital_composite',
        1 => 'horizontal_sync_positive',
        1 => 'vertical_sync_positive',
        1 => '',
    ) ],

    standard_timing => [ _group_by2(
        8 => 'X',
        2 => 'aspect',
        6 => 'vfreq',
    ) ],
    monitor_range => [ _group_by2(
        8 => 'vertical_min',
        8 => 'vertical_max',
        8 => 'horizontal_min',
        8 => 'horizontal_max',
        8 => 'pixel_clock_max',
    ) ],

    manufacturer_specified_range_timing => [ _group_by2(
        # http://www.spwg.org/salisbury_march_19_2002.pdf
        # for the glossary: http://www.vesa.org/Public/PSWG/PSWG15v1.pdf
        8 => 'horizontal_sync_pulse_width_min', # HSPW (Horizontal Sync Pulse Width)
        8 => 'horizontal_sync_pulse_width_max',
        8 => 'horizontal_back_porch_min', # t_hbp
        8 => 'horizontal_back_porch_max',
        8 => 'vertical_sync_pulse_width_min', # VSPW (Vertical Sync Pulse Width)
        8 => 'vertical_sync_pulse_width_max',
        8 => 'vertical_back_porch_min', # t_vbp (Vertical Back Porch)
        8 => 'vertical_back_porch_max',
        8 => 'horizontal_blanking_min', # t_hp (Horizontal Period)
        8 => 'horizontal_blanking_max',
        8 => 'vertical_blanking_min', # t_vp
        8 => 'vertical_blanking_max',
        8 => 'module_revision',
    ) ],
    
    cea_data_block_collection => [ _group_by2(
        3 => 'type',
        5 => 'size',
    ) ],

    cea_video_data_block => [ _group_by2(
        1 => 'native',
        7 => 'mode',
    ) ],
);

my @cea_video_mode_to_detailed_timing = (
    'pixel_clock',
    'horizontal_active',
    'vertical_active',
    'aspect',
    'horizontal_blanking',
    'horizontal_sync_offset',
    'horizontal_sync_pulse_width',
    'vertical_blanking',
    'vertical_sync_offset',
    'vertical_sync_pulse_width',
    'horizontal_sync_positive',
    'vertical_sync_positive',
    'interlaced'
);

my @cea_video_modes = (
# [0] pixel clock, [1] X, [2] Y, [3] aspect, [4] Hblank, [5] Hsync_offset, [6] Hsync_pulse_width,
# [7] Vblank, [8] Vsync_offset, [9] Vsync_pulse_width, [10] Hsync+, [11] Vsync+, [12] interlaced
# 59.94/29.97 and similar modes also have a 60.00/30.00 counterpart by raising the pixel clock
    [  25.175,  640,  480,  "4/3",  160,   16,  96,  45, 10,  2, 0, 0, 0 ], #  1:  640x 480@59.94
    [  27.000,  720,  480,  "4/3",  138,   16,  62,  45,  9,  6, 0, 0, 0 ], #  2:  720x 480@59.94
    [  27.000,  720,  480, "16/9",  138,   16,  62,  45,  9,  6, 0, 0, 0 ], #  3:  720x 480@59.94
    [  74.250, 1280,  720, "16/9",  370,  110,  40,  30,  5,  5, 1, 1, 0 ], #  4: 1280x 720@60.00
    [  74.250, 1920, 1080, "16/9",  280,   88,  44,  45,  4, 10, 1, 1, 1 ], #  5: 1920x1080@30.00
    [  27.000, 1440,  480,  "4/3",  276,   38, 124,  45,  8,  6, 0, 0, 1 ], #  6: 1440x 480@29.97
    [  27.000, 1440,  480, "16/9",  276,   38, 124,  45,  8,  6, 0, 0, 1 ], #  7: 1440x 480@29.97
    [  27.000, 1440,  240,  "4/3",  276,   38, 124,  22,  4,  3, 0, 0, 0 ], #  8: 1440x 240@60.05
    [  27.000, 1440,  240, "16/9",  276,   38, 124,  22,  4,  3, 0, 0, 0 ], #  9: 1440x 240@60.05
    [  54.000, 2880,  480,  "4/3",  552,   76, 248,  45,  8,  6, 0, 0, 1 ], # 10: 2880x 480@29.97
    [  54.000, 2880,  480, "16/9",  552,   76, 248,  45,  8,  6, 0, 0, 1 ], # 11: 2880x 480@29.97
    [  54.000, 2880,  240,  "4/3",  552,   76, 248,  22,  4,  3, 0, 0, 0 ], # 12: 2880x 240@60.05
    [  54.000, 2880,  240, "16/9",  552,   76, 248,  22,  4,  3, 0, 0, 0 ], # 13: 2880x 240@60.05
    [  54.000, 1440,  480,  "4/3",  276,   32, 124,  45,  9,  6, 0, 0, 0 ], # 14: 1440x 480@59.94
    [  54.000, 1440,  480, "16/9",  276,   32, 124,  45,  9,  6, 0, 0, 0 ], # 15: 1440x 480@59.94
    [ 148.500, 1920, 1080, "16/9",  280,   88,  44,  45,  4,  5, 1, 1, 0 ], # 16: 1920x1080@60.00
    [  27.000,  720,  576,  "4/3",  144,   12,  64,  49,  5,  5, 0, 0, 0 ], # 17:  720x 576@50.00
    [  27.000,  720,  576, "16/9",  144,   12,  64,  49,  5,  5, 0, 0, 0 ], # 18:  720x 576@50.00
    [  74.250, 1280,  720, "16/9",  700,  440,  40,  30,  5,  5, 1, 1, 0 ], # 19: 1280x 720@50.00
    [  74.250, 1920, 1080, "16/9",  720,  528,  44,  45,  4, 10, 1, 1, 1 ], # 20: 1920x1080@25.00
    [  27.000, 1440,  576,  "4/3",  288,   24, 126,  49,  4,  6, 0, 0, 1 ], # 21: 1440x 576@25.00
    [  27.000, 1440,  576, "16/9",  288,   24, 126,  49,  4,  6, 0, 0, 1 ], # 22: 1440x 576@25.00
    [  27.000, 1440,  288,  "4/3",  288,   24, 126,  24,  2,  3, 0, 0, 0 ], # 23: 1440x 288@50.08
    [  27.000, 1440,  288, "16/9",  288,   24, 126,  24,  2,  3, 0, 0, 0 ], # 24: 1440x 288@50.08
    [  54.000, 2880,  576,  "4/3",  576,   48, 252,  49,  4,  6, 0, 0, 1 ], # 25: 2880x 576@25.00
    [  54.000, 2880,  576, "16/9",  576,   48, 252,  49,  4,  6, 0, 0, 1 ], # 26: 2880x 576@25.00
    [  54.000, 2880,  288,  "4/3",  576,   48, 252,  24,  2,  3, 0, 0, 0 ], # 27: 2880x 288@50.08
    [  54.000, 2880,  288, "16/9",  576,   48, 252,  24,  2,  3, 0, 0, 0 ], # 28: 2880x 288@50.08
    [  54.000, 1440,  576,  "4/3",  288,   24, 128,  49,  5,  5, 0, 0, 0 ], # 29: 1440x 576@50.00
    [  54.000, 1440,  576, "16/9",  288,   24, 128,  49,  5,  5, 0, 0, 0 ], # 30: 1440x 576@50.00
    [ 148.500, 1920, 1080, "16/9",  720,  528,  44,  45,  4,  5, 1, 1, 0 ], # 31: 1920x1080@50.00
    [  74.250, 1920, 1080, "16/9",  830,  638,  44,  45,  4,  5, 1, 1, 0 ], # 32: 1920x1080@24.00
    [  74.250, 1920, 1080, "16/9",  720,  528,  44,  45,  4,  5, 1, 1, 0 ], # 33: 1920x1080@25.00
    [  74.250, 1920, 1080, "16/9",  280,   88,  44,  45,  4,  5, 1, 1, 0 ], # 34: 1920x1080@30.00
    [ 108.000, 2880,  480,  "4/3",  552,   64, 248,  45,  9,  6, 0, 0, 0 ], # 35: 2880x 480@59.94
    [ 108.000, 2880,  480, "16/9",  552,   64, 248,  45,  9,  6, 0, 0, 0 ], # 36: 2880x 480@59.94
    [ 108.000, 2880,  576,  "4/3",  576,   48, 256,  49,  5,  5, 0, 0, 0 ], # 37: 2880x 576@50.00
    [ 108.000, 2880,  576, "16/9",  576,   48, 256,  49,  5,  5, 0, 0, 0 ], # 38: 2880x 576@50.00
    [  72.000, 1920, 1080, "16/9",  384,   32, 168, 170, 46, 10, 1, 0, 1 ], # 39: 1920x1080@25.00
    [ 148.500, 1920, 1080, "16/9",  720,  528,  44,  45,  4, 10, 1, 1, 1 ], # 40: 1920x1080@50.00
    [ 148.500, 1280,  720, "16/9",  700,  440,  40,  30,  5,  5, 1, 1, 0 ], # 41: 1280x 720@100.00
    [  54.000,  720,  576,  "4/3",  144,   12,  64,  49,  5,  5, 0, 0, 0 ], # 42:  720x 576@100.00
    [  54.000,  720,  576, "16/9",  144,   12,  64,  49,  5,  5, 0, 0, 0 ], # 43:  720x 576@100.00
    [  54.000, 1440,  576,  "4/3",  288,   24, 126,  49,  4,  6, 0, 0, 0 ], # 44: 1440x 576@50.00
    [  54.000, 1440,  576, "16/9",  288,   24, 126,  49,  4,  6, 0, 0, 0 ], # 45: 1440x 576@50.00
    [ 148.500, 1920, 1080, "16/9",  280,   88,  44,  45,  4, 10, 1, 1, 1 ], # 46: 1920x1080@60.00
    [ 148.500, 1280,  720, "16/9",  370,  110,  40,  30,  5,  5, 1, 1, 0 ], # 47: 1280x 720@120.00
    [  54.000,  720,  480,  "4/3",  138,   16,  62,  45,  9,  6, 0, 0, 0 ], # 48:  720x 480@119.88
    [  54.000,  720,  480, "16/9",  138,   16,  62,  45,  9,  6, 0, 0, 0 ], # 49:  720x 480@119.88
    [  54.000, 1440,  480,  "4/3",  276,   38, 124,  45,  8,  6, 0, 0, 1 ], # 50: 1440x 480@59.94
    [  54.000, 1440,  480, "16/9",  276,   38, 124,  45,  8,  6, 0, 0, 1 ], # 51: 1440x 480@59.94
    [ 108.000,  720,  576,  "4/3",  144,   12,  64,  49,  5,  5, 0, 0, 0 ], # 52:  720x 576@200.00
    [ 108.000,  720,  576, "16/9",  144,   12,  64,  49,  5,  5, 0, 0, 0 ], # 53:  720x 576@200.00
    [ 108.000, 1440,  576,  "4/3",  288,   24, 126,  49,  4,  6, 0, 0, 1 ], # 54: 1440x 576@100.00
    [ 108.000, 1440,  576, "16/9",  288,   24, 126,  49,  4,  6, 0, 0, 1 ], # 55: 1440x 576@100.00
    [ 108.000,  720,  480,  "4/3",  138,   16,  62,  45,  9,  6, 0, 0, 0 ], # 56:  720x 480@239.76
    [ 108.000,  720,  480, "16/9",  138,   16,  62,  45,  9,  6, 0, 0, 0 ], # 57:  720x 480@239.76
    [ 108.000, 1440,  480,  "4/3",  276,   38, 124,  45,  8,  6, 0, 0, 1 ], # 58: 1440x 480@119.88
    [ 108.000, 1440,  480, "16/9",  276,   38, 124,  45,  8,  6, 0, 0, 1 ], # 59: 1440x 480@119.88
    [  59.400, 1280,  720, "16/9", 2020, 1760,  40,  30,  5,  5, 1, 1, 0 ], # 60: 1280x 720@24.00
    [  74.250, 1280,  720, "16/9", 2680, 2420,  40,  30,  5,  5, 1, 1, 0 ], # 61: 1280x 720@25.00
    [  74.250, 1280,  720, "16/9", 2020, 1760,  40,  30,  5,  5, 1, 1, 0 ], # 62: 1280x 720@30.00
    [ 297.000, 1920, 1080, "16/9",  280,   88,  44,  45,  4,  5, 1, 1, 0 ], # 63: 1920x1080@120.00
    [ 297.000, 1920, 1080, "16/9",  720,  528,  44,  45,  4, 10, 1, 1, 0 ], # 64: 1920x1080@100.00
);

sub _within_limit {
    my ($value, $type, $limit) = @_;
    $type eq 'min' ? $value >= $limit : $value <= $limit;
}

sub _get_many_bits {
    my ($s, $field_name) = @_;
    my @bits = split('', unpack('B*', $s));
    my %h;
    foreach (@{$subfields{$field_name}}) {
        my ($size, $field) = @$_;
        my @l = ('0' x (8 - $size), splice(@bits, 0, $size));
        $h{$field} = unpack("C", pack('B*', join('', @l))) if $field && $field !~ /^_/;
    }
    \%h;
}

sub check_parsed_edid {
    my ($edid) = @_;

    $edid->{edid_version} >= 1 && $edid->{edid_version} <= 2 or return 'bad edid_version';
    $edid->{edid_revision} != 0xff or return 'bad edid_revision';

    if ($edid->{monitor_range}) {
        $edid->{monitor_range}{horizontal_min} && 
          $edid->{monitor_range}{horizontal_min} <= $edid->{monitor_range}{horizontal_max} 
            or return 'bad HorizSync';
        $edid->{monitor_range}{vertical_min} &&
          $edid->{monitor_range}{vertical_min} <= $edid->{monitor_range}{vertical_max} 
            or return 'bad VertRefresh';
    }

    '';
}

sub _build_detailed_timing {
    my ($pixel_clock, $vv) = @_;

    my $h = _get_many_bits($vv, 'detailed_timing');
    $h->{pixel_clock} = $pixel_clock / 100; # to have it in MHz
    my %detailed_timing_field_size = map { $_->[1], $_->[0] } @{$subfields{detailed_timing}};
    foreach my $field (keys %detailed_timing_field_size) {
        $field =~ s/_hi$// or next;
        my $hi = delete($h->{$field . '_hi'});
        $h->{$field} += $hi << $detailed_timing_field_size{$field};
    }
    $h;
}

sub _add_standard_timing_modes {
    my ($edid, $v) = @_;

    my @aspect2ratio = (
        $edid->{edid_version} > 1 || $edid->{edid_revision} > 2 ? '16/10' : '1/1',
        '4/3', '5/4', '16/9',
    );
    $v = [ map {
        my $h = _get_many_bits($_, 'standard_timing');
        $h->{X} = ($h->{X} + 31) * 8;
        if ($_ ne "\x20\x20" && $h->{X} > 256) { # cf VALID_TIMING in Xorg edid.h
            $h->{vfreq} += 60;
            if ($h->{ratio} = $aspect2ratio[$h->{aspect}]) {
                delete $h->{aspect};
                $h->{Y} = $h->{X} / eval($h->{ratio});
            }
            $h;
        } else { () }
    } unpack('a2' x (length($v) / 2), $v) ];
    $v;
}

sub parse_edid {
    my ($raw_edid, $verbose) = @_;

    my %edid;
    my ($main_edid, @eedid_blocks) = unpack("a128" x (length($raw_edid) / 128), $raw_edid);
    my @vals = unpack(join('', map { $_->[0] } @edid_info), $main_edid);
    my $i;
    foreach (@edid_info) {
        my ($field, $v) = ($_->[1], $vals[$i++]);

        if ($field eq 'year') {
            $v += 1990;
        } elsif ($field eq 'manufacturer_name') {
            my $h = _get_many_bits($v, 'manufacturer_name');
            $v = join('', map { chr(ord('A') + $h->{$_} - 1) } 1 .. 3);
            $v = "" if $v eq "@@@";
        } elsif ($field eq 'video_input_definition') {
            $v = _get_many_bits($v, 'video_input_definition');
        } elsif ($field eq 'feature_support') {
            $v = _get_many_bits($v, 'feature_support');
        } elsif ($field eq 'established_timings') {
            my $h = _get_many_bits($v, 'established_timings');
            $v = [
                sort { $a->{X} <=> $b->{X} || $a->{vfreq} <=> $b->{vfreq} }
                map { /(\d+)x(\d+)_(\d+)(i?)/ ? { X => $1, Y => $2, vfreq => $3, $4 ? (interlace => 1) : () } : () }
                grep { $h->{$_} } keys %$h ];
        } elsif ($field eq 'standard_timings') {
            $v = _add_standard_timing_modes(\%edid, $v);
        } elsif ($field eq 'monitor_details') {
            while ($v) {
                (my $pixel_clock, my $vv, $v) = unpack("v a16 a*", $v);

                if ($pixel_clock) {
                    # detailed timing
                    my $h = _build_detailed_timing($pixel_clock, $vv);
                    push @{$edid{detailed_timings}}, $h
                      if $h->{horizontal_active} > 1 && $h->{vertical_active} > 1;
                } else {
                    (my $flag, $vv) = unpack("n x a*", $vv);

                    if ($flag == 0xfd) {
                        # range
                        $edid{monitor_range} = _get_many_bits($vv, 'monitor_range');
                        if ($edid{monitor_range}{pixel_clock_max} == 0xff) {
                            delete $edid{monitor_range}{pixel_clock_max};
                        } else {
                            $edid{monitor_range}{pixel_clock_max} *= 10; #- to have it in MHz
                        }
                    } elsif ($flag == 0xf) {
                        my $range = _get_many_bits($vv, 'manufacturer_specified_range_timing');

                        my $e = $edid{detailed_timings}[0];
                        my $valid = 1;
                        foreach my $m ('min', 'max') {
                            my %total;
                            foreach my $dir ('horizontal', 'vertical') {
                                $range->{$dir . '_sync_pulse_width_' . $m} *= 2;
                                $range->{$dir . '_back_porch_' . $m} *= 2;
                                $range->{$dir . '_blanking_' . $m} *= 2;
                                if ($e && $e->{$dir . '_active'}
                                    && _within_limit($e->{$dir . '_blanking'}, $m, $range->{$dir . '_blanking_' . $m})
                                    && _within_limit($e->{$dir . '_sync_pulse_width'}, $m, $range->{$dir . '_sync_pulse_width_' . $m})
                                    && _within_limit($e->{$dir . '_blanking'} - $e->{$dir . '_sync_offset'} - $e->{$dir . '_sync_pulse_width'},
                                            $m, $range->{$dir . '_back_porch_' . $m})) {
                                    $total{$dir} = $e->{$dir . '_active'} + $range->{$dir . '_blanking_' . $m};
                                }
                            }
                            if ($total{horizontal} && $total{vertical}) {
                                my $hfreq = $e->{pixel_clock} * 1000 / $total{horizontal};
                                my $vfreq = $hfreq * 1000 / $total{vertical};
                                $range->{'horizontal_' . ($m eq 'min' ? 'max' : 'min')} = _round($hfreq);
                                $range->{'vertical_' . ($m eq 'min' ? 'max' : 'min')} = _round($vfreq);
                            } else {
                                $valid = 0;
                            }
                        }
                        $edid{$valid ? 'monitor_range' : 'manufacturer_specified_range_timing'} = $range;

                    } elsif ($flag == 0xfa) {
                        push @{$edid{standard_timings}}, _add_standard_timing_modes(\%edid, unpack('a12', $vv));
                    } elsif ($flag == 0xfc) {
                        my $prev = $edid{monitor_name};
                        $edid{monitor_name} = ($prev ? "$prev " : '') . unpack('A13', $vv);
                    } elsif ($flag == 0xfe) {
                        push @{$edid{monitor_text}}, unpack('A13', $vv);
                    } elsif ($flag == 0xff) {
                        push @{$edid{serial_number2}}, unpack('A13', $vv);
                    } else {
                       $verbose && $vv ne "\0" x 13 && $vv ne " " x 13 and
                         warn "parse_edid: unknown flag $flag\n";
                    }
                }
            }
        }

        $edid{$field} = $v if $field && $field !~ /^_/;
    }

    foreach (@eedid_blocks) {
        my ($tag, $v) = unpack("C a*", $_);

        if ($tag == 0x02) { # CEA EDID
            my $dtd_offset;
            ($dtd_offset, $v) = unpack("x C x a*", $v);

            next if $dtd_offset < 4;
            $dtd_offset -= 4;

            while ($dtd_offset > 0) {
                my $h = _get_many_bits($v, 'cea_data_block_collection');
                $dtd_offset -= $h->{size} + 1;

                my $vv;
                ($vv, $v) = unpack("x a$h->{size} a*", $v);
                if ($h->{type} == 0x02) { # Video Data Block
                    my @vmodes = unpack("a" x $h->{size}, $vv);
                    foreach my $vmode (@vmodes) {
                        $h = _get_many_bits($vmode, 'cea_video_data_block');
                        my $cea_mode = $cea_video_modes[$h->{mode} - 1];
                        if (!$cea_mode) {
                            warn "parse_edid: unhandled CEA mode $h->{mode}\n" if $verbose;
                            next;
                        }
                        my %det_mode = (source => 'cea_vdb');
                        @det_mode{@cea_video_mode_to_detailed_timing} = @$cea_mode;
                        push @{$edid{detailed_timings}}, \%det_mode;
                    }
                }
            }

            while (length($v) >= 18) {
                (my $pixel_clock, my $vv, $v) = unpack("v a16 a*", $v);
                last if !$pixel_clock;
                my $h = _build_detailed_timing($pixel_clock, $vv);
                push @{$edid{detailed_timings}}, $h
                    if $h->{horizontal_active} > 1 && $h->{vertical_active} > 1;
            }
        } else {
            $verbose && warn "parse_edid: unknown tag $tag\n";
        }
    }

    $edid{max_size_precision} = 'cm';
    $edid{EISA_ID} = $edid{manufacturer_name} . sprintf('%04x', $edid{product_code}) if $edid{product_code} && $edid{manufacturer_name};

    if ($edid{monitor_range}) {
        $edid{HorizSync} = $edid{monitor_range}{horizontal_min} . '-' . $edid{monitor_range}{horizontal_max};
        $edid{VertRefresh} = $edid{monitor_range}{vertical_min} . '-' . $edid{monitor_range}{vertical_max};
    }

    if ($edid{max_size_vertical}) {
        $edid{ratio} = $edid{max_size_horizontal} / $edid{max_size_vertical};
        $edid{ratio_name} = _ratio_name($edid{max_size_horizontal}, $edid{max_size_vertical}, 'cm');
        $edid{ratio_precision} = 'cm';
    }
    
    if ($edid{feature_support}{has_preferred_timing} && $edid{detailed_timings}[0]) {
        $edid{detailed_timings}[0]{preferred} = 1;
    }

    foreach my $h (@{$edid{detailed_timings}}) {

        # EDID standard is ambiguous on how interlaced modes should be
        # specified; workaround clearly broken modes:
        if ($h->{interlaced}) {
            foreach ("720x480", "1440x480", "2880x480", "720x576", "1440x576", "2880x576", "1920x1080") {
                if ($_ eq $h->{horizontal_active} . 'x' . $h->{vertical_active} * 2) {
                    $h->{vertical_active} *= 2;
                    $h->{vertical_blanking} *= 2;
                    $h->{vertical_sync_offset} *= 2;
                    $h->{vertical_sync_pulse_width} *= 2;
                    $h->{vertical_blanking} |= 1;
                }
            }
        }

        # if the mm size given in the detailed_timing is not far from the cm size
        # put it as a more precise cm size
        my %in_cm = (
            horizontal => _define($h->{horizontal_image_size}) / 10,
            vertical   => _define($h->{vertical_image_size}) / 10,
        );
        my ($error) = sort { $b <=> $a } map { abs($edid{'max_size_' . $_} - $in_cm{$_}) } keys %in_cm;
        if ($error <= 0.5) {
            $edid{'max_size_' . $_} = $in_cm{$_} foreach keys %in_cm;
            $edid{max_size_precision} = 'mm';
        }
        if ($error < 1 && $in_cm{vertical}) {
            # using it for the ratio
            $edid{ratio} = $in_cm{horizontal} / $in_cm{vertical};
            $edid{ratio_name} = _ratio_name($in_cm{horizontal}, $in_cm{vertical}, 'mm');
            $edid{ratio_precision} = 'mm';
        }

        $h->{bad_ratio} = 1 if abs($edid{ratio} - $h->{horizontal_active} / $h->{vertical_active}) > ($edid{ratio_precision} eq 'mm' ? 0.02 : 0.2);

        if ($edid{max_size_vertical}) {
            $h->{vertical_dpi} = $h->{vertical_active} / $edid{max_size_vertical} * 2.54;
        }
        if ($edid{max_size_horizontal}) {
            $h->{horizontal_dpi} = $h->{horizontal_active} / $edid{max_size_horizontal} * 2.54;
        }
        my $dpi_string = '';
        if ($h->{vertical_dpi} && $h->{horizontal_dpi}) {
            $dpi_string = 
              abs($h->{vertical_dpi} / $h->{horizontal_dpi} - 1) < 0.05 ? 
                sprintf("%d dpi", $h->{horizontal_dpi}) :
                sprintf("%dx%d dpi", $h->{horizontal_dpi}, $h->{vertical_dpi});
        }

        my $horizontal_total = $h->{horizontal_active} + $h->{horizontal_blanking};
        my $vertical_total = $h->{vertical_active} + $h->{vertical_blanking};

        no warnings 'uninitialized';
        $h->{ModeLine_comment} = sprintf qq(# Monitor %s%s modeline (%.1f Hz vsync, %.1f kHz hsync, %sratio %s%s)),
          $h->{preferred} ? "preferred" : "supported",
          $h->{source} eq 'cea_vdb' ? " CEA" : '',
          $h->{pixel_clock} / $horizontal_total / $vertical_total * 1000 * 1000 * ($h->{interlaced} ? 2 : 1),
          $h->{pixel_clock} / $horizontal_total * 1000,
          $h->{interlaced} ? "interlaced, " : '',
          _nearest_ratio($h->{horizontal_active} / $h->{vertical_active}, 0.01) || sprintf("%.2f", $h->{horizontal_active} / $h->{vertical_active}),
          $dpi_string ? ", $dpi_string" : '';
          
        $h->{ModeLine} = sprintf qq("%dx%d" $h->{pixel_clock} %d %d %d %d %d %d %d %d %shsync %svsync%s),
          $h->{horizontal_active}, $h->{vertical_active},

          $h->{horizontal_active},
          $h->{horizontal_active} + $h->{horizontal_sync_offset}, 
          $h->{horizontal_active} + $h->{horizontal_sync_offset} + $h->{horizontal_sync_pulse_width},
          $horizontal_total,

          $h->{vertical_active},
          $h->{vertical_active} + $h->{vertical_sync_offset}, 
          $h->{vertical_active} + $h->{vertical_sync_offset} + $h->{vertical_sync_pulse_width},
          $vertical_total,

          $h->{horizontal_sync_positive} ? '+' : '-',
          $h->{vertical_sync_positive} ? '+' : '-',
          $h->{interlaced} ? ' Interlace' : '';
    }

    $edid{diagonal_size} = sqrt(_sqr($edid{max_size_horizontal}) + 
                                _sqr($edid{max_size_vertical})) / 2.54;

    \%edid;
}

sub _nearest_ratio {
    my ($ratio, $max_error) = @_;
    my @sorted = 
      sort { $a->[1] <=> $b->[1] }
        map { 
            my $error = abs($ratio - eval($_));
            $error > $max_error ? () : [ $_, $error ];
        } @known_ratios;
    $sorted[0][0];
}

sub _ratio_name {
    my ($horizontal, $vertical, $precision) = @_;
    
    if ($precision eq 'mm') {
        _nearest_ratio($horizontal / $vertical, 0.1);
    } else {
        my $error = 0.5;
        my $ratio1 = _nearest_ratio(($horizontal + $error) / ($vertical - $error), 0.2);
        my $ratio2 = _nearest_ratio(($horizontal - $error) / ($vertical + $error), 0.2);
        $ratio1 && $ratio2 or return;
        if ($ratio1 eq $ratio2) {
            $ratio1;
        } else {
            my $ratio = _nearest_ratio($horizontal / $vertical, 0.2);
            join(' or ', $ratio, $ratio eq $ratio1 ? $ratio2 : $ratio1);
        }
    }
}

sub _edid_from_lines {
    my (@l) = @_;
    my $edid_str = join('', map { /\s+([0-9a-f]{32})$/ && $1 } @l);
    if (length($edid_str) % (2 * 128) != 0 || length($edid_str) == 0) {
        return ();
    }
    pack("C*", map { hex($_) } $edid_str =~ /(..)/g);
}

sub find_edid_in_string {
    my ($input) = @_;

    my @edids;
    while ($input =~ /(?:EDID_DATA|: EDID \(in hex\)|EDID):\n((.*\n){8})/g) {
        push @edids, _edid_from_lines(split '\n', $1);
    }
    if (!@edids) {
        @edids = _edid_from_lines(split '\n', $input);
    }
    @edids;
}

sub _define { defined $_[0] ? $_[0] : 0 }
sub _sqr { $_[0] * $_[0] }
sub _round { int($_[0] + 0.5) }
sub _group_by2 {
    my @l;
    for (my $i = 0; $i < @_; $i += 2) {
        push @l, [ $_[$i], $_[$i+1] ];
    }
    @l;
}

1;
__END__

=head1 NAME

Parse::EDID - Extended display identification data (EDID) parser

=head1 DESCRIPTION

This module provides some function to parse Extended Display Identification
Data binary data structures.

=head1 FUNCTIONS

=head2 parse_edid($raw_edid)

Parse the raw binary edid data, as a string, and return a corresponding data
structure, as an hashref.

=head2 check_parsed_edid($edid)

Check the data structure, and return an error message if anything is wrong,  an
empty string otherwise.

=head2 find_edid_in_string($string)

Extract raw binary edid data from another tool text output, such as xrandr
--prop.