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How to process image sequences with VideoStitch Studio (eg: time-lapse)?


While image sequences are not yet supported in VideoStitch Studio, it is still possible to process image sequence projects by modifying the .ptv file or by converting the image sequence to a video.


 

1st method: Convert the image sequence into videos and process as videos

You can process image sequences in VideoStitch Studio by converting them into footage then processing them as standard videos.

Prerequisite :

  • Images from your image sequence are named the following way: imagename-001.png ... imagename-999.png (or imagename-0001.png .... imagename-9999.png and so on)
  • You have FFmpeg installed on your computer ( it can be downloaded here: https://ffmpeg.org/)

In this example, I will use 6 image sequences from 6 GoPro cameras

The command to convert your images to a video compatible with VideoStitch Studio is the following:

ffmpeg -framerate yourframerate -i imagename-%0Nd.png -pxl_fmt yuv420p videoname.mp4

The general form %0Nd where N is a number larger than zero determines how many digits there are in your file name.

In our case, we have 625 frames per camera and we want to create a 29.97 framerate videos.

The command would be : ffmpeg -framerate 29.97 -i cam1-%03d.png -pxl_fmt yuv420p cam1.mp4 for our first sequence of images up to ffmpeg -framerate 29.97 -i cam6-%03d.png -pxl_fmt yuv420p cam6.mp4 for the sixth image sequence

You then have 6 videos that you can use as inputs in VideoStitch Studio (File > Open Videos):

You can then calibrate and process your videos like as you would do with usual videos (VideoStitch Studio user guide can be found here)

If you want to get an image sequence as output, you can select an image format as the output format:

You will then have one stitched image for each frame: 

Example of stitched frame

 

 

 

2nd method: Modify the ptv file

You can stitch time-lapse footage by editing the *.ptv file manually too, here's how:

  1. Open the VideoStitch Studio project (*.ptv file) with a text editor.
  2. Replace each input file name property by the name containing an image sequence pattern.
  3. Open the project in VideoStitch Studio (use Ctrl+F5 to reload the current project).


The pattern can be used anywhere in the file name and follow this convention:

%0ni

% - marks the beginning of the pattern.

0 - the 'blank' character used by the pattern, usually zero.

n - an integer (0~9) the length of the pattern.

i - marks the end of the pattern.

For example:

%03i: 000, 001, 002, 003 ...
%05i: 00000, 00001, 00002, 00003 ...

The file name is on line 40 in this example:

im_sequence.jpg

 For which this pattern ../%03i_A.jpg describes the following image sequence:

../000_A.jpg
../001_A.jpg
../002_A.jpg
../003_A.jpg

 

The project will open normally in VideoStitch Studio. However, there's one limitation:

  • If your image sequence doesn't start from 0 VideoStitch Studio won't auto detect the first frame. To overcome this limitation, you can set the project's first_frame parameter directly in your *.ptv file.
  • Make sure to keep a backup of the project you've manually edited. And use the "save a copy and send to batch" option for processing. This will avoid overwriting the first_frame parameter when working on your project.

 

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