fixsrt.rb

#!/usr/bin/env ruby

# SRT Subtitle fixer v0.5
# Applies a time or id shift to an SRT subtitle file.
# 
# (C) 2008 [email protected]
# 
# Usage: ./fixsrt file.srt <timeshift> [idshift]
# - timeshift: time shift in floating point (seconds)
# - idshift:   subtitle id shift, integer, useful
#              when cutting unneeded subs. defaults to 0.
#
# Results are printed to stdout.
#
$KCODE = 'u'

def fixsrt(file, timeshift, idshift)
    File.read(file).split("\n").map do |line|
        if line =~ /^(\d{2}:\d{2}:\d{2},\d{3}) --> (\d{2}:\d{2}:\d{2},\d{3})/
            sprintf "%s --> %s", $1.shift_srt_ts(timeshift), $2.shift_srt_ts(timeshift)
        elsif line =~ /^\d+/
            ($&.to_i + idshift).to_s
        else
            line
        end
    end
end

class String
    def to_seconds
        return nil unless self =~ /^(\d{2}):(\d{2}):(\d{2}),(\d{3})/
        h, m, s, d = $1, $2, $3, $4
        ret = "0.#{d}".to_f
        ret += s.to_i
        ret += m.to_i * 60
        ret += h.to_i * 3600
        ret
    end

    def shift_srt_ts(shift)
        (self.to_seconds + shift).to_srt_ts
    end
end

class Float
    def to_srt_ts
        h = (self/3600).to_i
        m = ((self - h*3600)/60).to_i
        s = (self - h*3600 - m*60).to_i
        d = ((self - self.to_i) * 1000).to_i
        sprintf "%02d:%02d:%02d,%03d", h, m, s, d
    end
end

if $0 == __FILE__
  raise "Usage: #$0 <file> <timeshift> [idshift]" unless ARGV.size > 1

  file = ARGV.shift
  timeshift = ARGV.shift.to_f
  idshift = ARGV.shift.to_i

  raise "#{file}: invalid file" unless File.file? file
  raise "#{timeshift}: invalid timeshift" if timeshift.zero?

  puts fixsrt(file, timeshift, idshift)
end