How to Convert Equirectangular to Cubemap in FFmpeg

This article provides a quick guide on how to use FFmpeg’s v360 filter to convert 360-degree video from equirectangular projection to cubemap projection. You will find the exact command-line syntax, explanations of the essential parameters, and examples of different cubemap layouts to help you achieve the best video quality and compatibility.

The v360 filter in FFmpeg is a powerful tool designed for converting between various 360-degree video projections. To convert a standard equirectangular video to a cubemap, you must define the input projection as equirectangular and the output projection as a cubemap format.

The Basic Command

The simplest command to perform this conversion uses the standard equirect input and the cube output parameters. By default, this generates a 6x1 cubemap layout (six cube faces aligned in a single horizontal row).

ffmpeg -i input.mp4 -vf "v360=input=equirect:output=cube" output.mp4

Choosing Cubemap Layouts

The standard 6x1 strip can result in an extremely wide video that some hardware decoders struggle to play. To solve this, you can specify alternative cubemap layouts using different output names:

• 3x2 Cubemap (c3x2): Arranges the six faces in a 3-column, 2-row grid. This is highly recommended for better video player compatibility.

  ffmpeg -i input.mp4 -vf "v360=input=equirect:output=c3x2" output.mp4

• 1x6 Cubemap (c1x6): Arranges the faces in a single vertical column.

  ffmpeg -i input.mp4 -vf "v360=input=equirect:output=c1x6" output.mp4

Enhancing Output Quality

When converting projections, pixels are mapped to new coordinates, which can introduce aliasing or blurriness. You can control the quality of this mapping using the interp (interpolation) parameter.

The default interpolation is bilinear, but you can use lanczos or bicubic for sharper, higher-quality results:

ffmpeg -i input.mp4 -vf "v360=input=equirect:output=c3x2:interp=lanczos" output.mp4

Customizing Face Order (Optional)

If your target video player requires a specific order for the cube faces (Right, Left, Up, Down, Front, Back), you can use the out_forder parameter. The default face order is rludfb. To change it, specify the letters in your preferred sequence:

ffmpeg -i input.mp4 -vf "v360=input=equirect:output=c3x2:out_forder=lru肩fb" output.mp4

(Note: l = Left, r = Right, u = Up/Top, d = Down/Bottom, f = Front, b = Back)