Class: Timecode

Inherits:
Object
  • Object
show all
Includes:
Comparable
Defined in:
lib/timecode.rb

Overview

Timecode is a convenience object for calculating SMPTE timecode natively. The promise is that you only have to store two values to know the timecode - the amount of frames and the framerate. An additional perk might be to save the dropframeness, but we avoid that at this point.

You can calculate in timecode objects ass well as with conventional integers and floats. Timecode is immutable and can be used as a value object. Timecode objects are sortable.

Here’s how to use it with ActiveRecord (your column names will be source_tc_frames_total and tape_fps)

composed_of :source_tc, :class_name => 'Timecode',
  :mapping => [%w(source_tc_frames total), %w(tape_fps fps)]

Defined Under Namespace

Classes: CannotParse, Error, RangeError, WrongFramerate

Constant Summary collapse

VERSION = 
'0.2.0'
DEFAULT_FPS = 
25.0
NTSC_FPS =

:stopdoc:

(30.0 * 1000 / 1001).freeze
ALLOWED_FPS_DELTA = 
(0.001).freeze
COMPLETE_TC_RE = 
/^(\d{2}):(\d{2}):(\d{2}):(\d{2})$/
DF_TC_RE = 
/^(\d{1,2}):(\d{1,2}):(\d{1,2});(\d{2})$/
FRACTIONAL_TC_RE = 
/^(\d{2}):(\d{2}):(\d{2}).(\d{1,8})$/
WITH_FRACTIONS_OF_SECOND = 
"%02d:%02d:%02d.%02d"
WITH_FRAMES = 
"%02d:%02d:%02d:%02d"

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(total = 0, fps = DEFAULT_FPS) ⇒ Timecode

Initialize a new Timecode object with a certain amount of frames and a framerate will be interpreted as the total number of frames

Raises:



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# File 'lib/timecode.rb', line 47

def initialize(total = 0, fps = DEFAULT_FPS)
  raise WrongFramerate, "FPS cannot be zero" if fps.zero?
  
  # If total is a string, use parse
  raise RangeError, "Timecode cannot be negative" if total.to_i < 0
  # Always cast framerate to float, and num of rames to integer
  @total, @fps = total.to_i, fps.to_f
  @value = validate!
  freeze
end

Class Method Details

.at(hrs, mins, secs, frames, with_fps = DEFAULT_FPS) ⇒ Object

Initialize a Timecode object at this specfic timecode



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# File 'lib/timecode.rb', line 120

def at(hrs, mins, secs, frames, with_fps = DEFAULT_FPS)
  validate_atoms!(hrs, mins, secs, frames, with_fps)
  total = (hrs*(60*60*with_fps) +  mins*(60*with_fps) + secs*with_fps + frames).round
  new(total, with_fps)
end

.from_seconds(seconds_float, the_fps = DEFAULT_FPS) ⇒ Object

create a timecode from the number of seconds. This is how current time is supplied by QuickTime and other systems which have non-frame-based timescales



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# File 'lib/timecode.rb', line 156

def from_seconds(seconds_float, the_fps = DEFAULT_FPS)
  total_frames = (seconds_float.to_f * the_fps.to_f).to_i
  new(total_frames, the_fps)
end

.from_uint(uint, fps = DEFAULT_FPS) ⇒ Object

Some systems (like SGIs) and DPX format store timecode as unsigned integer, bit-packed. This method unpacks such an integer into a timecode.



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# File 'lib/timecode.rb', line 163

def from_uint(uint, fps = DEFAULT_FPS)
  tc_elements = (0..7).to_a.reverse.map do | multiplier | 
    ((uint >> (multiplier * 4)) & 0x0F)
  end.join.scan(/(\d{2})/).flatten.map{|e| e.to_i}

  tc_elements << fps
  at(*tc_elements)
end

.new(from, fps = DEFAULT_FPS) ⇒ Object

Use initialize for integers and parsing for strings



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# File 'lib/timecode.rb', line 65

def new(from, fps = DEFAULT_FPS)
  from.is_a?(String) ? parse(from, fps) : super(from, fps)
end

.parse(input, with_fps = DEFAULT_FPS) ⇒ Object

Parse timecode entered by the user. Will raise if the string cannot be parsed. The following formats are supported:

  • 10h 20m 10s 1f (or any combination thereof) - will be disassembled to hours, frames, seconds and so on automatically

  • 123 - will be parsed as 00:00:01:23

  • 00:00:00:00 - will be parsed as zero TC



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# File 'lib/timecode.rb', line 79

def parse(input, with_fps = DEFAULT_FPS)
  # Drop frame goodbye
  if (input =~ DF_TC_RE)
    raise Error, "We do not support drop-frame TC"
  # 00:00:00:00
  elsif (input =~ COMPLETE_TC_RE)
    atoms_and_fps = input.scan(COMPLETE_TC_RE).to_a.flatten.map{|e| e.to_i} + [with_fps]
    return at(*atoms_and_fps)
  # 00:00:00.0
  elsif input =~ FRACTIONAL_TC_RE
    parse_with_fractional_seconds(input, with_fps)
  # 10h 20m 10s 1f 00:00:00:01 - space separated is a sum of parts
  elsif input =~ /\s/
    parts = input.gsub(/\s/, ' ').split.reject{|e| e.strip.empty? }
    raise CannotParse, "No atoms" if parts.empty?
    parts.map{|part|  parse(part, with_fps) }.inject{|sum, p| sum + p.total }
  # 10s
  elsif input =~ /^(\d+)s$/
    return new(input.to_i * with_fps, with_fps)
  # 10h
  elsif input =~ /^(\d+)h$/i
    return new(input.to_i * 60 * 60 * with_fps, with_fps)
  # 20m
  elsif input =~ /^(\d+)m$/i
    return new(input.to_i * 60 * with_fps, with_fps)
  # 60f - 60 frames, or 2 seconds and 10 frames
  elsif input =~ /^(\d+)f$/i
    return new(input.to_i, with_fps)
  # Only a bunch of digits, treat 12345 as 00:01:23:45
  elsif (input =~ /^(\d+)$/)
    atoms_len = 2 * 4
    # left-pad input AND truncate if needed
    padded = input[0..atoms_len].rjust(8, "0")
    atoms = padded.scan(/(\d{2})/).flatten.map{|e| e.to_i } + [with_fps]
    return at(*atoms)
  else
    raise CannotParse, "Cannot parse #{input} into timecode, unknown format"
  end
end

.parse_with_fractional_seconds(tc_with_fractions_of_second, fps = DEFAULT_FPS) ⇒ Object

Parse a timecode with fractional seconds instead of frames. This is how ffmpeg reports a timecode



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# File 'lib/timecode.rb', line 142

def parse_with_fractional_seconds(tc_with_fractions_of_second, fps = DEFAULT_FPS)
  fraction_expr = /\.(\d+)$/
  fraction_part = ('.' + tc_with_fractions_of_second.scan(fraction_expr)[0][0]).to_f

  seconds_per_frame = 1.0 / fps.to_f
  frame_idx = (fraction_part / seconds_per_frame).floor

  tc_with_frameno = tc_with_fractions_of_second.gsub(fraction_expr, ":%02d" % frame_idx)

  parse(tc_with_frameno, fps)
end

.soft_parse(input, with_fps = DEFAULT_FPS) ⇒ Object

Parse timecode and return zero if none matched



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# File 'lib/timecode.rb', line 70

def soft_parse(input, with_fps = DEFAULT_FPS)
  parse(input) rescue new(0, with_fps)
end

.validate_atoms!(hrs, mins, secs, frames, with_fps) ⇒ Object

Validate the passed atoms for the concrete framerate



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# File 'lib/timecode.rb', line 127

def validate_atoms!(hrs, mins, secs, frames, with_fps)
  case true
    when hrs > 99
      raise RangeError, "There can be no more than 99 hours, got #{hrs}"
    when mins > 59
      raise RangeError, "There can be no more than 59 minutes, got #{mins}"
    when secs > 59
      raise RangeError, "There can be no more than 59 seconds, got #{secs}"
    when frames > (with_fps -1)
      raise RangeError, "There can be no more than #{with_fps -1} frames @#{with_fps}, got #{frames}"
  end
end

Instance Method Details

#*(arg) ⇒ Object

Multiply the timecode by a number

Raises:



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# File 'lib/timecode.rb', line 273

def *(arg)
  raise RangeError, "Timecode multiplier cannot be negative" if (arg < 0)
  self.class.new(@total*arg.to_i, @fps)
end

#+(arg) ⇒ Object

add number of frames (or another timecode) to this one



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# File 'lib/timecode.rb', line 251

def +(arg)
  if (arg.is_a?(Timecode) && framerate_in_delta(arg.fps, @fps))
    self.class.new(@total+arg.total, @fps)
  elsif (arg.is_a?(Timecode))
    raise WrongFramerate, "You are calculating timecodes with different framerates"
  else
    self.class.new(@total + arg, @fps)
  end
end

#-(arg) ⇒ Object

Subtract a number of frames



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# File 'lib/timecode.rb', line 262

def -(arg)
  if (arg.is_a?(Timecode) &&  framerate_in_delta(arg.fps, @fps))
    self.class.new(@total-arg.total, @fps)
  elsif (arg.is_a?(Timecode))
    raise WrongFramerate, "You are calculating timecodes with different framerates"
  else
    self.class.new(@total-arg, @fps)
  end
end

#/(arg) ⇒ Object

Get the number of times a passed timecode fits into this time span (if performed with Timecode) or a Timecode that multiplied by arg will give this one



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# File 'lib/timecode.rb', line 285

def /(arg)
  arg.is_a?(Timecode) ?  (@total / arg.total) : self.class.new(@total /arg, @fps)
end

#<=>(other_tc) ⇒ Object

Timecodes can be compared to each other



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# File 'lib/timecode.rb', line 290

def <=>(other_tc)
  if framerate_in_delta(fps, other_tc.fps)
    self.total <=> other_tc.total
  else 
    raise WrongFramerate, "Cannot compare timecodes with different framerates"
  end
end

#convert(new_fps) ⇒ Object

Convert to different framerate based on the total frames. Therefore, 1 second of PAL video will convert to 25 frames of NTSC (this is suitable for PAL to film TC conversions and back).



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# File 'lib/timecode.rb', line 231

def convert(new_fps)
  self.class.new(@total, new_fps)
end

#fps ⇒ Object

get FPS



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# File 'lib/timecode.rb', line 184

def fps
  @fps
end

#frame_interval ⇒ Object

get frame interval in fractions of a second



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# File 'lib/timecode.rb', line 209

def frame_interval
  1.0/@fps
end

#framerate_in_delta(one, two) ⇒ Object

Validate that framerates are within a small delta deviation considerable for floats



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# File 'lib/timecode.rb', line 310

def framerate_in_delta(one, two)
  (one.to_f - two.to_f).abs <= ALLOWED_FPS_DELTA
end

#frames ⇒ Object

get the number of frames



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# File 'lib/timecode.rb', line 189

def frames
  value_parts[3]
end

#hours ⇒ Object

get the number of hours



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# File 'lib/timecode.rb', line 204

def hours
  value_parts[0]
end

#inspect ⇒ Object

:nodoc:



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# File 'lib/timecode.rb', line 58

def inspect # :nodoc:
  "#<Timecode:%s (%dF@%.2f)>" % [to_s, total, fps]
end

#minutes ⇒ Object

get the number of minutes



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# File 'lib/timecode.rb', line 199

def minutes
  value_parts[1]
end

#seconds ⇒ Object

get the number of seconds



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# File 'lib/timecode.rb', line 194

def seconds
  value_parts[2]
end

#succ ⇒ Object

Get the next frame



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# File 'lib/timecode.rb', line 279

def succ
  self.class.new(@total + 1, @fps)
end

#to_f ⇒ Object

get total frames as float



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# File 'lib/timecode.rb', line 241

def to_f
  @total
end

#to_i ⇒ Object

get total frames as integer



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# File 'lib/timecode.rb', line 246

def to_i
  @total
end

#to_s ⇒ Object

get formatted SMPTE timecode



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# File 'lib/timecode.rb', line 236

def to_s
  WITH_FRAMES % value_parts
end

#to_seconds ⇒ Object

get the timecode as a floating-point number of seconds (used in Quicktime)



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# File 'lib/timecode.rb', line 224

def to_seconds
  (@total / @fps)
end

#to_uint ⇒ Object

get the timecode as bit-packed unsigned 32 bit int (suitable for DPX and SGI)



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# File 'lib/timecode.rb', line 214

def to_uint
  elements = (("%02d" * 4) % [hours,minutes,seconds,frames]).split(//).map{|e| e.to_i }
  uint = 0
  elements.reverse.each_with_index do | p, i |
    uint |= p << 4 * i 
  end
  uint
end

#total ⇒ Object

get total frame count



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# File 'lib/timecode.rb', line 179

def total
  to_f
end

#with_frames_as_fraction ⇒ Object Also known as: with_fractional_seconds

FFmpeg expects a fraction of a second as the last element instead of number of frames. Use this method to get the timecode that adheres to that expectation. The return of this method can be fed to ffmpeg directly.

Timecode.parse("00:00:10:24", 25).with_frames_as_fraction #=> "00:00:10.96"



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# File 'lib/timecode.rb', line 302

def with_frames_as_fraction
  vp = value_parts.dup
  vp[-1] = (100.0 / @fps) * vp[-1]
  WITH_FRACTIONS_OF_SECOND % vp
end

#zero? ⇒ Boolean

is the timecode at 00:00:00:00

Returns:

  • (Boolean) 


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# File 'lib/timecode.rb', line 174

def zero?
  @total.zero?
end