Module decode 

Turning compressed packets into pictures.

One trait, several backends, and a runtime choice between them. The choice is the interesting part: which decoder exists depends on the platform and on what was compiled in, and the two fail differently. A build without decode-av1 and a Linux box without VA-API both produce “no decoder”, and a person needs to know which one they are looking at — so open says.

Where the decoders come from

vtome reads two encodings, H.264 and AV1 (Encoding::is_in_scope); anything else is refused as out of scope before a backend is asked.

Backend	Platform	What it decodes for vtome
VideoToolbox	macOS, iOS	H.264, and AV1 on hardware that has it
Media Foundation	Windows	H.264, AV1
MediaCodec	Android	H.264, and AV1 where the device ships it
VA-API	Linux	whatever the driver exposes
dav1d	anywhere	AV1, in software

The platform decoders come first: they are hardware-accelerated, and the patent licence for H.264 is the operating system’s rather than ours. dav1d is the floor — it is what makes “vtome can always play AV1, which it writes” true everywhere.

What is implemented

H.264 through VideoToolbox (Apple targets), Media Foundation (Windows), and MediaCodec (Android), each with decode-platform. For everything else open refuses honestly, naming the backend that would have taken the work, rather than returning a decoder that produces nothing. See planning/TODO.md §2.

Structs

DecoderConfig

What a decoder needs to know before the first packet.

StubDecoder

A stub decoder for Phase 1 testing — returns empty frames.

Enums

Backend

Which implementation decodes.

Hardware

Whether a codec may, must, or must not use dedicated hardware — for decoding and for encoding alike.

Constants

BACKENDS

Every backend, in the order open tries them.

Traits

Decoder

Something that turns packets into frames.

Functions

backends_for

Which backends could decode this, here, in this build.

open

A decoder for this configuration.

open_with

open, with a say in whether the decoder runs in hardware.