Jezra.net: Time Lapse

Time Lapse

2015-04-08

Not too long ago, I purchased a programmable remote for my DSLR camera so that I could take long exposures as well as multiple exposures in order to create time lapse videos. While the timer does a great job, I still needed a way to convert a series of images into a video.

Fortunately, ffmpeg does a great job of converting a pile of images into a video file, and I most certainly have ffmpeg installed on my laptop. Now all I need is a bit of code to:

search for some files
copy and rename the files
always skip step 3 :)
use ffmpeg to convert the files to a video

When the script runs, it looks for a directory named 'images' and recursively looks for files in that directory (my camera tends to make multiple directories of files). Then the files are copied into a temp folder and given a 6 digit name: 000001, 000002, 000003, etc. Finally, ffmpeg converts those 6 digit named files into a video.

Enter The Ruby

#!/usr/bin/env ruby
require 'fileutils'
require 'date'

#where will we look for files?
LOCAL_DIR = File.expand_path( File.dirname(__FILE__) )
TEMP_DIR = File.join(LOCAL_DIR, "temp")
IMAGES_DIR = File.join(LOCAL_DIR, "images")
#if the temp dir exists, delete it and its contents
if Dir.exists? TEMP_DIR
    FileUtils.rm_rf TEMP_DIR
end

#make the temp dir
FileUtils.mkdir TEMP_DIR

#keep track of how many files we have
@file_count = 0

def copy_files(location)
  files = []
  dirs = []
  Dir.foreach(location) do |name|
    #ignore . and ..
    if name!='.' and name!='..'
      #what is the path of the item?
      path = File.join(location,name)
      #recurse if path is a directory
      if Dir.exists? path
        dirs << path
      else
        files << path
      end
    end
  end
  #sort the directories by name and recurse
  dirs = dirs.sort()
  dirs.each do |d|
    puts "DIRECTORY: #{d}"
    copy_files(d)
  end
  #sort the files by name and recurse
  files = files.sort()
  files.each do |d|
    new_name = @file_count.to_s
    #increment the file_count
    @file_count+=1
    ## pad the new file name with 0
    (6-new_name.length()).times do
      new_name = "0"+new_name
    end
    #determine where the new file is going
    new_file = File.join(TEMP_DIR, new_name)
    #what is the command to copy the file?
    copy_command = "cp #{d} #{new_file}"
    puts copy_command
    #run the command
    `#{copy_command}`
  end
end

#recursively get a list of all files in the current directory
copy_files(IMAGES_DIR)

#what day is it?
ymd = Date.today.strftime("%Y%m%d")

#what video command should we run?
cmd = "ffmpeg -y -f image2 -i temp/%06d -b:v 50000k  #{ymd}_timelapse.avi"
#run the command
`#{cmd}`

By default, the ffmpeg command will create a video at 10 frames/second.

My first time lapse was during Sunset on the Equinox

Sadly, I didn't adjust the camera properly when capturing the April 4th Lunar Eclipse. However, considering I set everything up 7 hours before the eclipse, I think I did a fairly sweet job of determining where to point the camera. :)

Now quit reading, slow down, and speed up.

Time Lapse from jezra.net

Comments

2015-04-22 Alison Chaiken:

'gst-launch multifilesrc location="somematchingstring"' would work as well.

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