To create a time-lapse video, you simply configure the Raspberry Pi to take a picture at a regular interval, such as every minute, then use an application to stitch the pictures together into a video.
There are a couple of ways of doing this.
The raspistill application has a built in time-lapse mode, using the --timelapse (or -tl) command line switch.
The value that follows the switch is the time between shots in milliseconds.
raspistill -t 30000 -tl 2000 -o image%04d.jpg
Note the %04d in the output filename: this indicates the point in the filename where you want a frame count number to appear. So, for example, the command above will produce a capture every two seconds (2000ms), over a total period of 30 seconds (30000ms), named image0001.jpg, image0002.jpg, and so on, through to image0015.jpg.
The %04d indicates a four-digit number, with leading zeroes added to make up the required number of digits. So, for example, %08d would result in an eight-digit number. You can miss out the 0 if you don't want leading zeroes.
If a timelapse value of 0 is entered, the application will take pictures as fast as possible. Note that there's an minimum enforced pause of approximately 30 milliseconds between captures to ensure that exposure calculations can be made.
A good way to automate taking a picture at a regular interval is using cron.
Open the cron table for editing:
crontab -e
This will either ask which editor you would like to use, or open in your default editor. Once you have the file open in an editor, add the following line to schedule taking a picture every minute (referring to the Bash script from the previous page):
* * * * * /home/pi/camera.sh 2>&1
Save and exit and you should see the message:
crontab: installing new crontab
Ensure your script does not save each picture taken with the same filename. This will overwrite the picture each time.
Now you'll need to stitch the photos together into a video.
You can do this on the Pi using mencoder but the processing will be slow. You may prefer to transfer the image files to your desktop computer or laptop and processing the video there.
Navigate to the folder containing all your images and list the file names in to a text file. For example:
ls *.jpg > stills.txt
Although it will be slow (due to encoding in software rather than using the Raspberry Pi hardware acceleration), you can stitch your JPEG images together using various available tools. This documentation will use avconv, which needs to be installed.
sudo apt-get install libav-tools
Now you can use the tools to convert your JPEG files in to an H264 video file.
avconv -r 10 -i image%04d.jpg -r 10 -vcodec libx264 -vf scale=1280:720 timelapse.mp4
On a Raspberry Pi 3, this can encode a little more than one frame per second. The performance of other Pi models will vary. The parameters used are:
- -r 10 Assume ten frames per second in input and output files.
- -i image%04.jpg The input file specification (to match the files produced during the capture).
- -vcodec libx264 Use the software x264 encoder.
- -vf scale=1280:720 Scale to 720p. You can also use 1920:1080, or lower resolutions, depending on your requirements. Note the Pi can only play back up to 1080p video, but if you are intending to play back at, for example, 4K, you could set that here.
- timelapse.mp4 The name of the output file.
avconv has a comprehensive parameter set for varying encoding options and other settings. These can be listed using avconv --help.
You can use the same instructions as for the Raspberry Pi, or an alternative package such as mencoder:
sudo apt-get install mencoder
Now run the following command:
mencoder -nosound -ovc lavc -lavcopts vcodec=mpeg4:aspect=16/9:vbitrate=8000000 -vf scale=1920:1080 -o timelapse.avi -mf type=jpeg:fps=24 mf://@stills.txt
Once that's completed, you should have a video file called timelapse.avi containing a time-lapse from your images.