Processor Ambi Grain

s3g Processor Ambi Grain 16 is a CLAP instrument for granulating loaded ACN/SN3D ambisonic files. It treats the file as one encoded sound field: grain position, duration, rate, direction, and envelope are shared across all active ambisonic channels.

Use it when you want clouds, freezes, scans, or stepped cuts from an already encoded 1OA, 2OA, or 3OA file while keeping the spatial image locked together.

Workflow

1. Insert s3g Processor Ambi Grain 16 on a correctly routed 16-channel Ambisonic track and set ORD to the intended 1OA, 2OA, or 3OA source order.
2. Follow it with an ambisonic decoder. Additional Ambisonic effects may be placed before the decoder when their supported order and channel count match the field.
3. Click LOAD and choose an ACN/SN3D ambisonic audio file.
4. Choose STORE PROJECT (the new-instance default), LINK, or EMBED below the waveform. Save the REAPER project to enable project-media collection.
5. Use the transport icons to play, pause/resume, or stop and return the scan/grain state to the start.

The output bus is fixed at 16 channels for third-order ambisonics. First-order and second-order modes use the matching lower channel counts and leave higher-order channels silent.

Sample Storage and Recall

Ambi Grain uses the shared Sample Storage policy. The storage selector, sample locator, RELINK button, and status are below the waveform; the waveform and grain controls retain their existing layout.

• PROJECT copies the unchanged source in the background into s3g Samples under the saved REAPER project's effective media directory. State stores a project-relative locator after collection, so moving the project together with its media does not depend on the original file path. Identical source copies are content-verified and reused.
• LINK retains an absolute file reference without collecting or embedding the audio. Keep that file available at the same location; use RELINK after moving it or transferring a linked session to another computer.
• EMBED includes decoded floating-point audio in the host's saved plugin state and in plugin presets. It preserves every loaded channel and the shared normalization data, without normalizing again on recall. The plugin bundle itself is never modified. Embedded audio is limited to 1 GiB per instance; larger assets require PROJECT or LINK.

PROJECT requires a saved REAPER project and supported project-media access. Until those are available, collection remains pending and playback continues using the loaded source. A pending file-backed sample remains path-referenced; an embedded sample being converted to project media keeps its audio in state until collection succeeds. Save again after the status reports that project media is ready. For REAPER Save As, enable a copy-media option if collected files should follow the new project.

Missing-file recall restores the settings and retains the missing locator, displays MISSING SAMPLE / RELINK, and does not play unrelated previously loaded audio. RELINK selects a replacement while preserving the recalled settings. Existing version-1 projects and presets with a source path restore as LINK; they are not silently converted or copied. Newly saved version-2 states require this updated plugin or newer.

A failed preset save leaves the previous preset file intact. Imports exceeding the decoded-audio cap in EMBED mode are rejected without replacing the current sample; select PROJECT or LINK before loading a larger asset.

Grain Model

When a file loads, the processor peak-normalizes the complete multichannel field to 0.95 with one shared gain. It never normalizes channels independently, so the ACN/SN3D level relationships and spatial image remain intact.

The processor uses one shared event stream. Each grain reads the same source time across every active ambisonic channel, applies the selected envelope, and writes into a circular multichannel tape layer before output.

This matters for ambisonics: the W, X, Y, Z, and higher-order channels are not independent audio stems. Keeping the grain timing shared helps preserve the encoded spatial relationships while still allowing dense granular motion.

Display

The waveform shows the loaded file as a source-time map. Grain markers show where events are being drawn from, and the jitter window shows the active source area used by modes that randomize grain position.

In SCAN, the source position moves through the file. In FREEZE, grains gather around a fixed source point. In JUMP, source position moves between stepped regions.

Controls

Routing

Use a 16-channel REAPER track for 3OA work and keep the active channels mapped one-to-one through the decoder. Lower orders occupy the corresponding first 4 or 9 channels while the remaining lanes stay silent.

Playback Guidelines

• Set ORD to match the loaded file. A wrong order will usually sound spatially wrong even if audio is present.
• High DENS with long GMS can create heavy overlap, so the plugin limits the available density range for stable playback.
• SCAN is best for moving through a full file; FREEZE is best for sustained texture; JUMP is best for rhythmic cuts between regions.