Trait CodecResolver 

pub trait CodecResolver: Sync {
    // Required method
    fn resolve_tag(&self, ctx: &ProbeContext<'_>) -> Option<CodecId>;

    // Provided method
    fn resolve_payload_magic(&self, first_bytes: &[u8]) -> Option<CodecId> { ... }
}

Resolve a CodecTag (FourCC / WAVEFORMATEX / Matroska id / …) to a CodecId. The oxideav-codec registry implements this, but defining the trait here lets containers consume tag resolution via &dyn CodecResolver without pulling in the codec crate as a direct dependency.

Inverse direction (codec_id → wire tag) is intentionally NOT a method on this trait. Wire tags are per-stream state: different mpeg4video streams correctly identify as DIVX / XVID / MP4V / FMP4, different h264 streams as H264 vs AVC1, and so on. The stream’s CodecParameters::tag field is the canonical home for that data — set by the demuxer when reading existing media and by the encoder via its output_params() at configure-time. A registry-level “give me the canonical tag for this codec_id” lookup walks registration order and returns whichever tag was declared first, which is arbitrary and breaks round-trip preservation.

Required Methods

fn resolve_tag(&self, ctx: &ProbeContext<'_>) -> Option<CodecId>

Resolve the tag in ctx.tag to a codec id. Implementations walk every registration whose tag set contains the tag, call each probe (treating None as “always 1.0”), and return the id with the highest resulting confidence. Ties are broken by registration order.

Provided Methods

fn resolve_payload_magic(&self, first_bytes: &[u8]) -> Option<CodecId>

Resolve a codec from a stream’s leading payload bytes, for carriage formats that announce the codec in the payload itself rather than through a container tag.

The canonical case is Ogg, which has no numeric codec tag at all: a logical stream announces its codec purely through a magic byte prefix at the start of the first packet (\x01vorbis, OpusHead, \x80theora, \x7fFLAC, Speex , …); raw elementary streams identified by a file head are the same shape. That identification model is prefix-shaped rather than exact-key-shaped, so it gets its own resolution entry point instead of a CodecTag form: codec crates declare the magic prefixes they answer to at registration time, and the caller hands the stream’s leading payload bytes (an Ogg demuxer: the first packet of a logical stream; a raw-stream prober: the file head — or however much of it is available) to this method. Implementations return the codec whose declared magic is a prefix of first_bytes, preferring the longest matching magic (most specific claim) and breaking remaining ties by registration order.

The default implementation resolves nothing, so existing resolver implementations (and NullCodecResolver) are unaffected.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors

impl CodecResolver for CodecRegistry

Implement the shared CodecResolver interface so container demuxers can accept &dyn CodecResolver without depending on this crate directly — the trait lives in oxideav-core.

impl CodecResolver for NullCodecResolver