Digital interleaving of stereo images — left and right frames merged sequentially or spatially for compatible playback. Essential post-production step for theatrical and home 3D distribution.
You're in the edit suite with two separate image streams in front of you — left eye, right eye, both in Full HD or 4K. Now comes the central question: How do you combine the two perspectives so that they diverge again on a 3D display (cinema projector, TV, VR headset) and each eye sees the correct image? That's stereoplexing — the digital interleaving of two images into one encoded data stream, which is decoded again at the end.
At its core, the process works according to a few established standards: Side-by-Side (SBS) places the left image on the left and the right image on the right — efficient for bandwidth, but halves the horizontal resolution per eye. Over-Under (OU) stacks them vertically, saving less resolution but requiring more storage with the same bitrate budget. Interlaced alternates between the eyes at the scanline level — historically relevant for 3D TVs, rarely used today. Checkerboard distributes pixels in a checkerboard pattern — storage efficient with some quality loss. On set or in post-production, you choose the format depending on the downstream requirement: A DCI cinema master needs different specifications than a streaming version or a Blu-ray 3D.
Practically: You export your final stereo layers from the VFX software or editing system — ideally decoupled, without compression between the takes. Then the material runs through a stereo encoder or multiplexer, which interleaves both streams according to the required standard. Pay attention to metadata: The final master needs exact information about disparity, convergence point, and which eye is on which side — otherwise, the viewer will be cross-eyed. Tip from practice: Always archive uncompressed or losslessly compressed stereo intermediate versions. You will need them later when format requirements change — and they always do.
A common problem: Time offset between left and right due to an asynchronous rendering pipeline or codec buffers. Stereoplexing must work with frame-accurate registrations. Therefore, the process usually runs as the final step before the master render — when all color correction, sound design, and VFX are already locked. Some post-production houses only do the plexing during DCP creation or streaming transcode, not before. This saves you storage space but costs flexibility later if corrections become necessary.