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Table of Contents

This section contains notes on creating timelapse video's using ffmpeg and a video source like a webcam.


An example timelapse of a 3D print taken with an Insta360 One R camera in webcam mode and ffmpeg

1 - Capture frames from a WebCam

Capture images from Webcam

Here we have a WebCam (Insta360 One-R with 4K camera mod) presenting itself as /dev/video1 on a Raspberry PI

To capture images every 10 seconds we can use:

1ffmpeg -f v4l2 -i /dev/video1 -r 1/10 out%08d.jpg

Here -i /dev/video1 is the camera's device, -r 1/10 is the capturing framerate, 1 in every 10 seconds and out%08d.jpeg is the filename for each frame generated.

Parameter Description
-f v4l2 Tell ffmpeg we are reading from v4l2 (Video For Linux 2)
-i /dev/video1 The V4L2 device of the camera to capture from
-r 1/10 The frame rate
out%08d.jpg The frame filename to write.

Here the frame rate is the capture rate in frames per second. So 1/10 means that we capture a single frame once every 10 seconds.

For the frame filename pattern, %08d will be replaced by the frame number, in this case 8 digits with leading 0's.

2 - Encode frames into MP4

Creating MP4 video from individual frames

To create an mp4 from these frames:

1ffmpeg -r 30 -start_number 1 -i out%08d.jpeg -c:v libx264 -r 30 -pix_fmt yuv420p out.mp4

Note there are two -r parameters for the frame rate. The first one is the source frame rate. The second one is the output frame rate of the final video.

Parameter Description Notes
-r 30 The source frame rate. This can be either lower than, equal or greater to the output rate
-start_number 1 The start frame number. This is optional and will default to 1 if omitted.
-i out%08d.jpeg The source frame filename format This should match that used to create the frames
-c:v libx264 Video encoding format
-r 30 Output frame rate
-pix_fmt yuv420p Output video frame format

For the source frame rate, do not confuse this with the capture frame rate. Instead, set it to how fast you want the source frames to be read in at when creating the video.

For example: When generating a 30fps video, and you want each frame image to be exactly one frame from the source then set it to 30 here and for the output frame rate.

If you want the output to be 30 fps but the input at just 10fps (so one source frame is 3 in the output) then set the input to 10 and the output as 30.

Setting the source to a value larger than the input will cause frames to be dropped from the source.