effectcraft/crates/aep

effectcraft-aep

After Effects projects (.aep, .aepx) in one crate, the way effectcraft-lottie handles Lottie:

• container: reads and writes the container as a lossless chunk tree, with a typed, read-only view (below; its API is re-exported at the crate root);
• import: maps the typed view into an EffectCraft project and reports everything it does not import (docs/aep-import.md).

Writing an EffectCraft project as an .aep (export) is not part of this crate yet.

No file access: callers pass bytes, so the crate builds for wasm32.

Container

An .aep is a RIFX container (big-endian RIFF) with form type Egg!: chunks of a 4-byte id, a big-endian u32 size and a body padded to an even length; LIST chunks start with a 4-byte list type followed by chunks. parse builds the tree, write serialises it, and for every input that parses, write(parse(x)) == x byte for byte (container and chunk sizes are recomputed from the tree; pad bytes, odd bodies and the bytes after the container, an XMP packet, are kept).

The XML form of a project (.aepx) is read into the same tree by read_aepx (a small bounded XML tokenizer, no dependency); parse_any picks the reader by content, so the typed view and the importer take either form. The mapping is in docs/aep-format.md, section 1.

Bodies that look like lists but are not chunk sequences (for example LIST btdk, raw text) stay opaque rather than failing the parse. Input is untrusted: sizes are checked against the remaining input, nesting and chunk count are bounded (Limits), nothing is allocated from a declared size, and truncated or damaged files return Err (or, inside the container, an opaque body).

The container layer decodes no chunk body. On top of it, a typed view (Project, Item, Comp, Layer, Property, ...) reads the fields whose layout was verified against the values the test files were made with: layer and composition headers (switches, exact times and time stretch, size, frame rate, work area, shutter phase, display start, renderer), static transform values in After Effects' units with the "absent = default" rule, keyframe records (interpolation sides, ease per component, plain and spatial templates), Time Remapping, expressions with their enable switch, effect instances and parameter values, masks and bezier paths with tangents, shape layer groups, text documents (paragraph and style runs, box, justification, tracking, faux styles, caps, leading), markers with duration, strings and cue data, cameras and lights with their options, footage (stills, audio, image sequences), solids and precomp links. Every accessor returns Option/an empty list on damaged data and never panics. Which fields are verified, which are not decoded, and how it was found is in docs/aep-format.md.

Specifications

Public specifications used for parts the format embeds:

• ICC.1:2010: the profile description of a working-space profile (a v2 desc or a v4 mluc tag), from which the working space's name is read (container/settings.rs).
• RFC 4648 (base64): the profile data in the project's colour settings JSON.

Clean room

Everything here comes from our own observations: project files that we generated ourselves with After Effects, one change per file, compared byte by byte. No source code or format documentation of another .aep reader or writer was used, and no Adobe asset is used. The test fixtures are such generated files (own test data): a few combined projects, one composition per case (tests/fixtures/CASES.md; the generator is in tests/fixtures/tools/). They are not in this repository but in storytold/effectcraft-corpus, with their attribution, the generation notes and the inspection of their embedded content. cargo xtask aep-corpus fetches them at the commit pinned in tests/fixtures/corpus.lock, checks every file against the SHA-256 listed there and only then installs them in corpus/aep (ignored by git). The tests read them from the folder named by the EFFECTCRAFT_AEP_FIXTURES environment variable (opt-in; set EFFECTCRAFT_AEP_FIXTURES_REQUIRED=1 too, so that a missing project fails). The tests reach them only through tests/it/common/mod.rs, which hands a test its case as a project of its own cut from the combined file; a test whose fixture is missing (or with the variable not set) prints SKIPPED: fixture <name> missing and passes.

tests/fixtures/synthetic.aep (115 KB) is the one project in the repository: made in After Effects 2026 with the working space set to None (one composition, an image sequence of three 8x8 PNGs, a solid, a folder, a Levels and a Glow effect with expressions). Every After Effects project embeds the working space's ICC profile (HP sRGB IEC61966-2.1 for the default) in a JSON settings chunk; the one Utf8 chunk of this file that held a profile was replaced by {}, and nothing else was changed. The tests in tests/it/import/synthetic.rs damage copies of it and need no other file.

Tools

• tests/fixtures/tools/: the generator of the test projects (regenerates the corpus with After Effects; its README says how).
• examples/aepdump.rs: prints the chunk tree of a file (ids, sizes, short data, match names): cargo run -p effectcraft-aep --example aepdump -- file.aep.
• examples/stubicc.rs: replaces every embedded ICC profile of a saved project by a stub that keeps only the profile's description: the JSON colorProfileData of the working space (any white space around the colon, \/ escapes, quotes as ") in an .aep chunk or the .aepx text, and a raw profile of an imported image (an .aep chunk, or the bdata hex of an .aepx): cargo run -p effectcraft-aep --example stubicc -- in.aep out.aep. A profile it cannot replace stops it before anything is written. The importer reads the working space's name from the description only, so the project imports the same; no vendor colour data stays in the test project. Check the result independently, not by the tool's count (the corpus repository has tools/aep/inspect-embedded.py, which scans the raw bytes, base64 and hex).