asciinema asciicast recording absolute/relative time converter for fine adjustments of output delays in post-production

asciicast-timestamp-converter.pl

#!/usr/bin/env perl
#===============================================================================
#
#         FILE: asciicast-timestamp-converter.pl
#
#        USAGE: ./asciicast-timestamp-converter.pl [filename]
#        USAGE: cat filename | ./asciicast-timestamp-converter.pl
#
#  DESCRIPTION: asciinema asciicast recording absolute/relative time converter
#               for fine adjustments of output delays in post-production
#===============================================================================

use strict;
use warnings;
use utf8;

$_=<>;
my $lt=0;

if (m/"version": 2/) { #native version
	s/"version": 2/"version": "2r"/;
	print;
	while(<>) {
		s/^\[(\d+(?:\.\d+)?),/sprintf "[%s,", $1-$lt/e;
		$lt=$1;
		print;
	}
} elsif (m/"version": "2r"/) { #relative version
	s/"version": "2r"/"version": 2/;
	print;
	while(<>) {
		s/^\[(\d+(?:\.\d+)?),/sprintf "[%s,", $1+$lt/e;
		$lt+=$1;
		print;
	}
}

To prevent the occasional display of scientific notation during the conversion, replace format mask %s with %f in lines 24 and 32.