Timelapse

Time Lapsing

I require long-term photography (for a worksite). I’ll be using an Android mobile phone (and power-bank or solar).

I settled on this process:

  1. App takes photos and saves locally
  2. App or sync uploads photos to Dropbox or similiar
  3. Cronjob runs every hour to:
    1. Combines 100s of images into a video, keeping all frames
    2. Deletes images (which are huge)
  4. Manually, I can check the videos, and choose to delete / edit / combine or slow down.

1. App to Take Photos

There’s a lot of apps, but few are suitable for longer-term use. The main problem is if the phone powers down without creating a video. There were good:

  • Timelapse Upload to Cloud
  • Timelapse 24/7
  • Open Camera

I use Open Camera which was really stable, has a simple timer feature and can set the focus. The timer is a countdown timer, so unfortunately images are 10s + photo time, which can vary. It has no scheduling or upload features.

Timelapse 24/7 was a bit buggy on my phone. It has better battery life, so would be good for 1 photo/min arrangement.

Timelapse Upload to Cloud was only a bit more stable. I didn’t use the Upload to Cloud function: this tries to upload immediately, requiring WiFi. Instead, I’ll run for 24hr, then turn on WiFi to upload in a batch.  Timelapse Upload to Cloud doesn’t add EXIF data to the images and occasionally crashed.

2. App to Upload

  • DropSync

Simple, solid.

3. Making movie from images

I wrote a command-line python program to do this.

It uses ffmpeg to create a movie. The Hx264 with defaults was a good format.

To deflicker, I used the ffmpeg deflicker filter when building the movie. The timelapse-defilter python script also worked well, but was slower.

Space and Time Requirements

Using the app below, I worked out a few scenarios. My details are:

  • 1920×1080 images: At 95% quality, this is about 0.3Mb.
  • ffmpeg encoding on defaults with H264 codec in AVI container.
  • No audio

I noted that:

  • 100fps or 24fps in the 1 hour video didn’t change the file size
  • At one photo per 10s, it’s 1Gb per day of images!
  • Convert to video, it’s 100Mb per day of videos
  • ffmpeg H264 defaults give 7000kbit/s (or ~1Mb/s?)

Choosing an interval:

  • 1s for driving, close people
  • 5s for sunsets, far people
  • 10s sun movement, or slow clouds
  • 1m plants
  • 10m construction (not activity)
Interval ThingDurationVideo Length Speedup
1sClose people1h2.5 min24x
5sFar people, fast clouds6h3 min120x
10sClose building, clouds6h6 min240x
30sSun,sky1day8 min 720x
1minPlants1 week7 min1440x
10minConstruction1 month3 min14400x

I selected 10s intervals for most things.

Real LengthInterval (s)# PhotosPhoto (Mb)Video Length
SpeedupVideoFPS (Max)VideoSize (Mb)
1h1036010012s3001008
10h (day)10360010002min30010050?
7 days (10h/day)?
1 month?

 

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