One of most common Raspberry PI accessories is the Raspberry PI Camera. Beside common usages (like videoconferencing), RPI gives a lot of advanced functions. One of most intrigating is getting a time lapse video from Raspberry PI camera
In this tutorial I’m going to show you how to create a time lapse video with a Raspberry PI board and Camera. We’ll use Raspicam commands to get images and ffmpeg library to create new time-lapse video.
Before digging in technical commands, a breaf introduction in what time lapse video is.
Time Lapse Technique
Looking a list of images projected on a screen, human eyes can’t distinguish interruption between an image (frame) and following one with a switch rate higher than 60 Frames Per Second (fps). On the other side, getting an illusion of continuous motion requires at least 10 fps (even if the optimal fps is supposed to 25). This uses the so called Persistence of Vision.
Time Lapse technique uses only some of still frames, extracting them from a video stream or capturing these frames from a camera with defined intervals. Still images, consolidaded on a smaller interva so that they can appear to human eye as a continuous flow, gives illusion that time is running faster on video.
In following picture this process is described with an example, where from a 15 fps (frame per second) we take 1 image every 5 and compress extracted images in a new video. Images that whould be showed after 5 seconds (from frame 76) will appear in new video file after 1 second:
What We Need
As usual, I suggest adding from now to your favourite ecommerce shopping chart all needed hardware, so that at the end you will be able to evaluate overall costs and decide if continuing with the project or removing them from shopping chart. So, hardware will be only:
- Raspberry PI 3 Model A+ (including proper power supply or using a smartphone micro usb charger with at least 3A) or newer Raspberry PI Board
- high speed micro SD card (at least 16 GB, at least class 10)
- Raspberry PI Camera
Check hardware prices with following links:
Start connecting your Camera module to Raspberry PI.
Prepare Operating System
Once installed, make your OS up to date. From terminal, use following command:
sudo apt update -y && sudo apt upgrade -y
We also need ffmpeg:
sudo apt install ffmpeg
Enable Raspberry PI Camera interface from raspi-config tool. From terminal:
Terminal will show following page:
Go to option 3 (Interface Option) and press ENTER:
Select fist option (Camera) and press ENTER. In next screen move selectio from “No” to “Yes”:
Press ENTER and confirm also in following screen.
You wil go back to raspi-config home. Move to finish button and press ENTER.
This operation will require a reboot. Confirm in next screen and wait for reboot:
Once your Raspberry PI is rebooted, connect again to terminal.
Create a folder where to store images and enter it:
mkdir timelapse cd timelapse
With following command we’ll capture images with defined intervals and save them with increasing naming:
raspistill -t 60000 -tl 2000 -o image%04d.jpg
In raspistill command, following parameters are used:
- -t 30000: this option will make command lasting for a total of 30 seconds
- -tl 2000: this option produces a capture (frame) every 2 seconds
- -o image%04d.jpg: every frame captures is saved as jpg file with names like image0001.jpg, image0002.jpg, image0003.jpg and so on. “%04d” indicates to use 4 digits with leading zeroes padding missing digits.
This will generate a list of jpg files inside current folder as expected:
pi@raspberrypi:~/timelapse $ ls image0000.jpg image0007.jpg image0014.jpg image0021.jpg image0028.jpg image0001.jpg image0008.jpg image0015.jpg image0022.jpg image0029.jpg image0002.jpg image0009.jpg image0016.jpg image0023.jpg image0030.jpg image0003.jpg image0010.jpg image0017.jpg image0024.jpg image0031.jpg image0004.jpg image0011.jpg image0018.jpg image0025.jpg image0005.jpg image0012.jpg image0019.jpg image0026.jpg image0006.jpg image0013.jpg image0020.jpg image0027.jpg
We are going now to create a text file including list of images that ffmpeg will put together creating final video. This will be created with following terminal command:
rm -f stills.txt; for f in image*.jpg; do echo "file '$f'" >> stills.txt; done
This is a short, one line, bash script. It removes stills.txt file if exists, then a common “for” loop reading list of files in current folder whose name starts with “image” and ends with “.jpg”. Wildcard “*” will consider good any character and any digits amount between those 2 strings. Each file name will be appended to a new stills.txt within a “file ‘……'” prefix. Output will be like following one:
pi@raspberrypi:~/timelapse $ cat stills.txt file 'image0000.jpg' file 'image0001.jpg' file 'image0002.jpg' file 'image0003.jpg' file 'image0004.jpg' file 'image0005.jpg' file 'image0006.jpg' file 'image0007.jpg' file 'image0008.jpg' file 'image0009.jpg' file 'image0010.jpg' file 'image0011.jpg' file 'image0012.jpg' file 'image0013.jpg' ....
Creating Time Lapse Video
Output (time-lapsed) video can be created from jpg images with following command:
ffmpeg -f concat -i stills.txt -s 1280x768 outVideo.mp4
- -f concat: uses concatenation demuxer
- -i stills.txt: -i option indicates input media. Referring a txt file, make possile getting input media from a file content
- -s 1280×768: sets output resolution
- outVideo.mp4: sets output file name
After this command you will find a new file named outVideo.mp4 which you can play in your favoutire media player (supporting mp4 format, like VLC).
As you can see, we already used -s option to reduce computing power required and make it compatible with a low hardware board like Raspberry PI. Ffmpeg requires a lot of RAM to run video manipulation. For this reason a Raspberry PI A+ could not manage long duration time-lapse videos at full resolution. When RAM problems occur, you will receive from terminal a “killed” notification and “journalctl -xe | grep ffmpeg” will return an Out of Memory error. In these cases, you have a few options:
- Change RPI swap file size
- reduce computing resources required by reducing output file quality (by tuning output frame rate, resolution, presets)
- move concatenation step on higher RAM computer (higher nRaspberry PI, notebook, desktop PC)
Following ones are 2 more options tat you can use with ffmpeg:
- -r: sets framerate (default value, if not specified “-r 30”). It can be used both for input media as for output media
- -preset: sets preset (default value, if not specified “-preset medium”). A preset is a collection of options that will provide a certain encoding speed to compression ratio. Available values are [ultrafast, superfast, veryfast, faster, fast, medium, slow, slower, veryslow, placebo]
Final Gift, Adding a Textbox on Time Lapse Video
A nice final feature for our video is adding a text box on it. Using again ffmpeg and tricks coming from Stackoverflow, we get a Text box with following terminal command:
ffmpeg -i outVideo.mp4 -vf drawtext="text='peppe8o.com': fontcolor=white: fontsize=24: box=1: firstname.lastname@example.org: boxborderw=5: x=(w-text_w)/2: y=(h-text_h)*4/5" -codec:a copy finOUT.mp4
Final Result Example
As final example for results, I’ve prepared a video vith a time lapse captured from 45 minutes, with 1 second between each image and restricting width and height to 1280×768 from jpg files:
raspistill -t 2700000 -tl 2000 -w 1280 -h 768 -o image%04d.jpg
Remaining steps follow commands provided in this tutorial. Resulting video can be showed in following:
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