SPLV (Voxel Video Codec)

SPLV is Outpaint's flagship volumetric video codec, discretizing an arbitrary 3D scene using voxels. I wrote the core spec, encoder, and decoder from-scratch in C. The codec leverages arithmetic coding, vector quantization, and inter-frame prediction to achieve a 20:1 compression ratio with near-lossless quality. To allow in-browser decoding, I targeted WebAssembly for compilation, and multithreaded it using SharedArrayBuffer + Web Workers. This coupled with the high compression ratio enabled real-time streaming and decoding of volumetric video on the web. To push the performance even further, I wrote a hardware-accelerated version of the decoder using WebGPU compute shaders, bit-identical to and 3x the performance of the WASM implementation. This powered all of the real-time demos used in Outpaint's seed raise.

Highlights

• 20:1 compression ratio with visually lossless quality, achieved with arithmetic coding, vector quantization, and P-frames.
• Multithreaded (SharedArrayBuffer + Web Workers) WebAssembly encoder + decoder, 6.5x faster than single-threaded at 8 cores.
• WebGPU decoder, 3x faster than the prior WASM implementation. Leveraged a block-parallel entropy decoder and a work-efficient prefix sum to achieve 10B voxels/s in-browser on consumer laptops.