# Compiled format 1.0

An `.avl` file is a single-codec, motion-only AVAL asset. A fixed 64-byte
header points to a canonical JSON manifest, fixed-width decode-chunk index, and
aligned elementary-stream payloads. The reader validates bounded UTF-8/JSON,
integer arithmetic, ranges, overlap, relations, digests, codec syntax,
geometry, dependencies, and presentation timing before playback.

The header identifies exactly wire `1.0`. There is no version dispatch or
compatibility interpretation.

## One codec per file

| Codec | Payload framing | Bit depth |
| --- | --- | --- |
| H.264 | Annex B access units | 8 |
| H.265/HEVC | Annex B access units | 8 |
| VP9 | codec frames/superframes | 8 |
| AV1 | low-overhead OBUs | 8 or 10 |

MP4, WebM, and IVF containers are not embedded. IVF is only an internal
compiler transport for FFmpeg VP9/AV1 stdout and is removed before writing the
asset.

## Decode and presentation timelines

Every unit/rendition span declares a decode-chunk count and displayed-frame
count. Its index records are in decoder submission order and contain:

- elementary payload offset and length;
- presentation timestamp and duration;
- random-access status; and
- the number of displayed frames produced by the chunk.

Codec inspection supplies the presentation-index mapping used by the runtime.
A unit starts at random access and is flushed before another unit is decoded.
Delayed/reordered output and hidden reference chunks are valid only when the
complete decoded presentation sequence exactly matches the unit's authored
frames. Cross-unit prediction is invalid.

## Manifest

The manifest contains the logical canvas, exact rational frame rate, authored
quality-ordered rendition ladder, units, state graph, bindings, readiness
closure, and declared resource limits. Renditions carry a fully qualified
WebCodecs codec string, bit depth, coded dimensions, opaque or stacked-alpha
rectangles, and measured bitrate.

Each codec alternative is a separate asset with its own integrity digest.
Ordered alternatives are an HTML authoring concern; wire 1.0 deliberately
does not impose cross-file identity or fallback policy.