StemSpace is an experimental foobar2000 AI-assisted stereo-to-7.1 DSP for Windows x64. This release publishes reviewed DSP source code and technical notes. It is not an installable or self-contained AI upmixer.
No model weights, ONNX Runtime DLL, compiled component, installer, private PDB, audio, user configuration or private research evidence is included. AI Stereo→7.1 requires separately and lawfully obtained compatible model and runtime prerequisites. Their availability and redistribution rights are not promised by this release. Without a ready model/runtime the DSP passes input through; that is not working AI upmixing.
- StableMix C retains the original stereo Mid/Side front image. Center comes only from original Mid; Vocals/Bass do not independently steer positioning. Drums/Other contribute to fixed Side/Rear routes. AI LFE is zero.
- Native non-stereo input bypasses the AI path, including mono, 5.1 and 7.1.
- The existing sample-rate adapter bridges the host rate and the fixed 44.1 kHz model clock. Offline regression coverage includes 44.1, 48 and 96 kHz; this is not a claim that every accepted rate has equivalent coverage.
- Scheduling retains a dedicated high-priority non-MMCSS worker, ORT intra-op 1 with spinning disabled, one batched 7.1 output per producing input callback, and a 250 ms start/flush prebuffer. Drained output can also be emitted at end of playback.
See StableMix C, building, offline validation and limits, and source provenance.
Mixer and streaming have passed the documented offline qualification within fixed inputs, toolchain and floating-point assumptions. These results do not establish listening quality, universal numerical equivalence, portable installation safety, or real foobar host/Spatial endpoint acceptance. The full release-validation gate remains BLOCKED. No new build or playback was performed to publish this snapshot.
Windows Spatial Output source and binaries are not included. They require separate source-rights and release acceptance work before a future delivery. This DSP does not depend on that output component. No third-party Spatial Output DLL is included.
The native meter publisher remains part of the DSP source. The standalone viewer is excluded from this preview. Publisher mappings use a Windows session-local namespace; running another instance in the same session is not safe isolation. See the limitations in the build notes before any future host testing.
The confirmed project-owned DSP, meter-publisher and local compatibility-shim scope uses the existing MIT license, copyright 2026 circerio. Adapted StemgenRT code retains Axel Delafosse's MIT notice. SDK/interface and other applicable notices remain separate; see THIRD_PARTY_NOTICES.md. The project MIT grant does not grant model, teacher, dataset, SDK/toolchain or third-party binary rights.
This repository starts with a fresh source-only history. It contains no inherited research branches, old binary assets or private repository history. SOURCE_MANIFEST.json records the reviewed source snapshot hashes; PUBLIC_FILE_MANIFEST.json lists the complete public payload except itself.