Stacking is a feature in SPIN Studio that allows you to upload raw video clips from supported VR cameras and "stack" them into one convenient file. At the time of this writing, SPIN Studio supports the stacking of two dual-cam 180VR cameras: the ZCAM K1 Pro and the Insta360 Evo.
With a stack you can render out dewarped 180 stereo footage with a color grade, adjusted horizontal FOV, offset vertical lens alignment, in/out trim points, and more. Stacks can even combine segmented clips, which are generated when cameras shoot long takes and cut up the recording into multiple files.
The benefit of a Stack is that you can render multiple shots in parallel with elastic computation delegation... which means that while your personal computer may only have 6 CPU cores (if that) to process one video at a time, on the SPIN Studio cloud platform you can utilize hundreds of CPU cores to render a dozen videos all at once, saving countless rendering hours.
A ZCAM K1 Pro
How to make a Stack
This is what a typical video shoot looks like: A bunch of raw video assets that now have just been offloaded from the SD cards to your local hard drive. Below are the files from just one lens.
Get started by creating a folder for your video shoot in your SPIN Studio account. Then upload the video files into your new folder. You do not need to upload each lens' video files into separate folders. They can live in the same destination -- but you must not change the original file name of the videos, otherwise it will not be possible to automatically pair lenses.
Here I have created a folder labeled "Raw 180 Sources" and have dragged-and-dropped 26 total video from both the Left and Right lenses of videos shot on a ZCAM K1 Pro.
2a. Manually creating a Stack
You can select two files that you know constitute a Left and Right eye of a single shot. Then you can hit 'Stack' and they will combine into one file.
2b. Automatically making Stacks in batch
This is the most efficient way to batch process many raw video assets. Once all the videos files from both the left and right lenses have been uploaded to the folder, navigate to the the left side to the parent folder. Click on the ellipses "breadcrumb" to reveal more options. Select 'Analyze And Stack'.
After analyzing, a list of all the shots will appear. Long takes segmented by the camera will be attached and concatenated to subsequent clips. Below, the the second section, both Camera 0001 and 0002 have two shots each, the first of which is 5:00 minutes long, which is when the ZCAM K1 Pro segments long takes.
You can quickly double check that the correct videos have been paired by visually comparing the thumbnails, and comparing each clip's duration. Sometimes a VR camera may record a few frames more on one lens than the other. Ultimately the final output length will be set to the shorter source video.
To continue, click 'Create Stacks' in the top right and stack all the videos (in this case, 6 of them).
3. Enter the FX editor
At this point you have made a stack. What was once two, four, or ten video files is now one manageable file.
But you cannot yet view the Stack because you have note rendered it nor given it any sort of visual color grade to make it pleasing to look at. This requires entering the FX editor on each Stack and adding those custom adjustments. To do this, click on the FX icon on the Stack.
4. The FX editor
In the FX editor you can adjust a range of properties of the Stack. You can change the camera rig calibration, and whether you want to dewarp into stereo top/bottom or left/right. The vertical offset operates on pixels. This will require some experimentation as each camera unit may have its own degree of offset between its left and right lenses.
The horizontal field of view slider is useful for cropping out the left or right lens visible in the wide FOV lenses. Whatever FOV you happen to land on will be playable in SPIN Play, even if it is set to a number like 162 degree like it is in the below image.
The trim property is measured in frames. By default it starts at frame 0 and ends on the last frame number of the video.
Apply custom-made LUTs and color effects from the drop down menu at the bottom and you will see a preview of the color changed in the preview window.
If you want to exit the FX editor at any point click the 'X' in the top right corner. Your changes will be saved for when the next time you open the Stack.
When you are happy with your shot you can hit 'Render' in the top right, give the encode a name, and return to the Library.
In the Library, you can see that your render in 'encoding'. SPIN Studio begins to dewarp and apply all the properties you applied in the FX editor. It also creates a bitrate ladder of the videos making it possible to stream and download on SPIN Play and spinxr.com. The number next to the encoding progress bar (here, 90), indicates the number of CPU cores delegated to rendering the Stack.
As the encode completes you can add the Stack to a Story or SPIN. As soon as it is done encoding you can play it back in SPIN Play or spinxr.com.
If you happen to manually Stack two clips together, and you incorrectly group two videos together, you can easily unstack clips and re-stack it with other videos. To do this select the clip in the Library and hit 'Unstack.'
If you would like to swap the Left/Right arrangement of the videos, before entering the FX editor and rendering, select the clip in the library, and open the right inspector pane. Under 'Stack sources' is an 'Update Sources' option will pop up a window that allows you to change the stereo mode as top/bottom or left/right, or select a new camera calibration, or swap left and right sources.
You can render multiple versions of a video in a Stack. Maybe you can play with the vertical offset, or change the color grade. Whenever you create a new render, you create another encode of the Stack. Below, I've named these two encodes "Version1" and "Version2", each with a different color grade. In the 'Share' section you will notice that I can select which encode to share out. Selecting a different encode from the drop down menu will yield that encode's respective nine-digit share key. This is important to keep in mind when sharing the video, as you want to ensure you are sharing the right version of your Stack.