#!/usr/bin/perl -wT

#######################
# Greg Hookey
#
# <g@deadly.ca>
#  
# Jan 18, 2004
#######################

use strict;

sub main() {

	my $chapter_index = 0;
	my @chapters;
	my $last_start = 1;

	my $filename = '';
	my $fps = 0;

	if( $#ARGV == 3 )
	{
		if( $ARGV[0] eq "-f" && $ARGV[2] eq "-x" )
		{
			$fps = $ARGV[1];
			$filename = $ARGV[3];
		} else {
			print_usage();
		}

	} elsif ( $#ARGV == -1 ) {
		exit 1;
	} else {
		print_usage();
	}

	open( XML, "< $filename" ) ||
		die "unable to open $filename for reading: $!";

	while( my $line = <XML> )
	{
		# The idea here is to skip along the xml file,
		# determining where chapters (seq) begin and
		# and (number of frames)
		
		if( grep( /<seq/, $line ) )
		{
			#print "open chapter\n";

			my $label = sprintf( "chapter%02d", $chapter_index );

			#print "$label\n";

			my $frame_accum = 0;

			while( $line = <XML> )
			{

				$_ = $line;

				if( m/\s*<video/ )
				{
					/\s*<video\ssrc=\"(.*?)\"\sclipBegin=\"(.*?)\"\sclipEnd=\"(.*?)\"\/>/;
					#print "$1 $2 $3\n";

					$frame_accum += ( ( $3 - $2 ) + 1 );		
				}
		
				# we've reached the end of the chapter
				if( grep( /<\/seq>/, $line ) )
				{
					#print "close chapter\n";
					last;
				}
			}

			if( $chapter_index == 0 )
			{
				$chapters[ $chapter_index ] = 1;
			} else {
				$chapters[ $chapter_index ] = $last_start;
			}
	
			$last_start += $frame_accum;

			$chapter_index++;
		}
		
	}

	close( XML );

	my $size = scalar( @chapters );
	my $timecode;

	for( my $i = 0; $i < $size; $i++ )
	{
		#print "Start frame: $frame_num\n";
		if( $i == 0 )
		{
			$timecode .= "0,";
		} elsif( $i == ( $size - 1 ) ) {
			$timecode = $timecode . make_timecode( $chapters[ $i ] - 1, $fps );
		} else {
			$timecode = $timecode . make_timecode( $chapters[ $i ] - 1, $fps ) . ',';
		}
	}	

	print "$timecode\n";
}

sub make_timecode() {

	return "error" if ! @_;

	( my $frame_no, my $fps ) = @_;

	my $timecode;
        my $hours = 0;
	my $mins = 0;
	my $secs = 0;
        my $cur = $frame_no;
	my $user_frame_rate = $fps;

        if ( $fps == 29 || $fps == 29.97 )
	{
                $fps = 30;
	}

        if ( $frame_no == 0 )
        {
                $hours = 0;
                $mins = 0;
                $secs = 0;
        }
        else
        {
		use integer;
		{
                	# NTSC drop-frame 
                	if ( $fps == 30 )
                	{
                        	my $max_frames = $cur;
                        	for ( my $j = 1800; $j <= $max_frames; $j += 1800 )
                        	{
                                	if ( $j % 18000 )
                                	{
                                        	$max_frames += 2;
                                        	$cur += 2;
                                	}
                        	}
                	}

                	$hours = $cur / ( $fps * 3600 );
                	$cur -= $hours * ( $fps * 3600 );
                	$mins = $cur / ( $fps * 60 );
                	$cur -= $mins * ( $fps * 60 );
                	$secs = $cur / $fps;
                	$cur -= $secs * $fps;
        	}
	}

	# compute fractional component this has to be done in floating point mode
	# so I've wrapped the integer math above in an anonymous block

	if( $fps == 30 ) 
	{
		$cur = $cur / $user_frame_rate * 100;
	} else {
		$cur = $cur / 25 * 100;
	}

	#print "hours: $hours mins: $mins secs: $secs frac: $cur\n";

        $timecode = sprintf( "%d:%2.2d:%2.2d%s%2.2d", $hours, $mins, $secs, ".", $cur );

        return $timecode;
}

sub print_usage() {
	print "usage: extract_chapters -f <fps> -x <file>\n";
	exit 1;
}

main();
