Module engine 

The compression engine contract and shared types.

Key architectural decision: core is designed around the Engine interface even while there is exactly one engine (media/ffmpeg). This lets us plug in images/PDF/office later without rewriting the skeleton.

Principle: Engine::plan is a pure, testable function (bitrate math); side effects are isolated in Engine::run.

Modules

media

Media engine v0.1: video + audio via ffmpeg (external process).

plan

The pure half of the media engine: planning an encode (video bitrate under a size target, quality mode, resolution / fps caps, the audio decision, output container, metadata tags) and the small calculations the run loop uses (the size-target ceiling, overshoot corrections). No ffmpeg — this is what builds without the ffmpeg feature (e.g. for iOS).

Structs

AudioSpec

Audio encoding parameters (absent means drop the track).

CaptureMeta

Capture metadata read from the source’s container tags. iPhone videos keep these as com.apple.quicktime.* keys; others use plain location / make / model / creation_time.

EncodePlan

The encode plan — the result of Engine::plan. Usable for --dry-run.

EncodeSpec

The full encode recipe.

MediaInfo

Source file metadata — the result of Engine::probe.

Outcome

The execution result — the result of Engine::run.

ShrinkOpts

Compression options passed to the engine — the decoded form of the flags.

VideoSpec

Video encoding parameters.

Enums

EngineError

Engine errors.

Hdr

HDR transfer function of a source video.

SizeGoal

What the user wants in terms of size.

Constants

MIN_SAVING

A quality-mode re-encode has to save at least this share of the source to be worth it; below that the original is kept. A minutes-long 4K encode for a 1 % saving isn’t a compression — just a generation of quality loss.

Traits

Engine

The compression engine contract. The one v0.1 implementation is media::MediaEngine.

Functions

not_worth_it

Whether a result of expected bytes isn’t worth producing for a source of source bytes (saves less than MIN_SAVING). The guard, dry runs and UI previews all ask this, so a preview and the run agree.