4dgs

4dgs is an open container format for 4D gaussian splat scenes that packages geometry, appearance, motion, audio, and camera into a single self-contained, seekable file. It uses length-prefixed records, temporal chunking, and a byte-range index to support streaming and indexed reads without requiring a sidecar file or loading the entire file into memory. The format includes native support for spatial audio sources with encoded audio, timing, gain, and fixed or moving 3D poses. It is designed to be renderer-agnostic, reconstructing state at a given time while leaving drawing and mixing to the renderer.

The format is designed for scenes where gaussians have properties such as position, opacity, and existence that vary continuously over time. It supports optional spatial audio sources whose 3D poses can move over time and includes a default camera trajectory. By using continuous time, each gaussian carries its own birth time, temporal extent, motion, and validity window, so the number of live gaussians varies over time with no frame machinery. This allows displaying an arbitrary instant by reading only the ranges that instant needs from the file's own index.

The format supports SDKs in five languages: Python, TypeScript, Rust, C++, and Swift. Support is stated per feature rather than per language, and the feature support matrix records only what the conformance suite proves. A partial SDK is documented as a state rather than a defect, ensuring that users know exactly which capabilities are available for their specific use case. The conformance suite and independent implementations are provided to verify adherence to the specification.

The format includes native support for spatial audio sources, which carry encoded audio, timing, gain, and fixed or moving 3D poses. The scene clock stays authoritative, ensuring that audio playback remains synchronized with the visual elements even as they move over time. A scene without audio carries nothing at all, meaning the format is flexible enough to omit audio entirely if not required. This design ensures that audio and visual elements are seamlessly integrated within the same file structure.

The format declares lossy encodings with stated error bounds, specifying the maximum deviation a decoder may observe per attribute. The encoder is expected to verify these bounds to ensure that the reconstructed scene remains within acceptable limits. This transparency allows developers to understand the trade-offs between compression and fidelity when working with the format. It also ensures that the format can be used in applications where approximate accuracy is sufficient.

The format is designed to be forward compatible by construction, using length-prefixed, opcode-tagged records that allow readers to skip unrecognized structures. This means that new features can be added without breaking existing readers or requiring changes to the core format. The conformance suite and independent implementations help ensure that the format evolves in a controlled manner, maintaining backward compatibility with older versions. This approach supports long-term maintenance and adoption across different platforms.

The official website of 4dgs is 4dgs.dev.

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