Converting a set of pictures into a video in Debian

(potentially as a part of time-lapse photography, as was the case here)

Updated 2014-05-17

On one of my trips to the upper peninsula of Michigan, I set up my Canon PowerShot SX100IS with CHDK's built-in intervalometer script, giving me a picture every 30 seconds of a 9-hour trip. This is the method I used on my Debian box to convert that series of images to a video.

One of the challenges was that the pictures ended up in two folders for some reason. My camera followed the all-too-familiar 121CANON/IMG_xxxx.JPG naming scheme, but somewhere in the middle, it wrote to 122CANON/IMG_xxxx.JPG as well. This is a problem because the tool I'll be using to convert to video expects the files to have sequential numbering; this is how it will determine the order. The files in this 122CANON folder are sequenced entirely differently. Happily, the camera's real-time clock battery was good, and each file was given a valid modification time...this is what I'll use to re-order the images into one sequence.

So I hacked together a Python (v2, not v3, just because) script to first rename each file from IMG_xxxx to simply its number of seconds since epoch. It looks like this:

import os.path, time, datetime
import shutil
import glob
os.chdir("/path/to/timelapse/122CANON")
for file in glob.glob("./*.JPG"):
    nicename = repr(os.path.getmtime(file))
    shutil.copyfile(file,"/path/to/timelapse/renamed/"+nicename+".jpg")

I changed the path on that 4th line and reran the script for each folder. I could then sort by name and get them chronologically ordered in the renamed folder. (Amusingly enough, there was a ".0" in the filename of everything because the time-since-epoch is stored as a float and I couldn't be bothered to look up which formatting command rounds to nearest whole number.) Now to give them sequential numbers.

import os.path, time, datetime
import shutil
import glob
os.chdir("/path/to/timelapse/renamed")
sortedNames = sorted(glob.glob("./*.jpg"))
idx = 0
for file in sortedNames:
    nicename = "%04d" % idx
    idx += 1
    shutil.move(file,nicename+".jpg")

Now we have a folder with nice sequential names. Time to run the video converter.

avconv -r 30 -i %04d.jpg -s hd480 -vcodec libx264 time-lapse.mp4

After several minutes of churning, I got what I came here for--a 1-minute video file, where each frame was an image from the time lapse I took. The -r value is frames per second, so slowing that down would make the video longer and make each image display for a longer time. The %04d.jpg is how we get the indexed images into the converter. The other options I just copy-pasted from here (apparently ffmpeg is now called avconv. Huh). I'm sure there's infinite tweakability here, but I don't care to look into it.

If you have questions/comments, contact me via jarau at mtu dot educational TLD.