Module ticket 

The owned codec ticket — one stream’s AVCodecParameters, mirrored into plain Rust and rebuilt on demand.

Why the mirror exists

ffmpeg_next::codec::Parameters is a *mut AVCodecParameters behind a Send-but-not-Sync wrapper. A track row that stores one is !Sync, an Arc of that row is !Send, and every consumer that shares a track table across tasks stops compiling — for a struct FFmpeg documents as a plain descriptor with no thread affinity at all. The auto-trait is missing, not the safety.

The crate already answers that class one way: it mirrors what a consumer needs into owned Rust — TrackParams mirrors the common seats, SideDataEntry mirrors a frame’s metadata, FfmpegBytes mirrors its pixels. CodecTicket walks that road its last mile: every seat of an AVCodecParameters, held as owned bytes and plain integers, with Sync arriving by construction rather than by an unsafe impl over FFI.

The two halves

• CodecTicket::mirror reads a live AVCodecParameters into the ticket. It is the only place that reads one.
• CodecTicket::rebuild allocates a fresh AVCodecParameters and writes every seat back. It is the only place in this crate’s track-row road that allocates one, and what it hands back is what avcodec_parameters_to_context is fed — unchanged from before the mirror existed.

The pair is proved in tests/codec_ticket_parity.rs: for every stream of every fixture the corpus can mint, the rebuilt struct is compared with the original field by field, including extradata bytes, the AV_INPUT_BUFFER_PADDING_SIZE zeroes past their end, every coded_side_data entry’s type id and payload, and the channel layout down to a custom map’s per-channel names. The shapes no container will hand over — a custom map, an unnamed side-data kind, every scalar set off its default — are built by hand in the same file, and a decoder is opened through a rebuilt ticket and made to produce a frame.

The reading discipline, inherited

Not one bindgen enum is materialised out of FFmpeg memory. Every open C enum seat — the media type, the codec id, the field order, the five colour seats, the alpha mode, the channel order, a custom channel’s id, a side-data type id — travels as the raw 32-bit pattern it is on the wire, read and written through the same i32 cast, so a value this build’s bindings cannot name is still a value this ticket carries. That is the same rule [crate::extras::bounded_clone_parameters] is written to, for the same reason: forming a typed reference to a struct whose enum field holds an unnamed discriminant is undefined behaviour before a single field is read.

Structs

ChannelLayoutTicket

The owned mirror of an AVChannelLayout.

CodecTicket

Every seat of one stream’s AVCodecParameters, owned.

CustomChannel

One entry of a custom channel map — the AV_CHANNEL_ORDER_CUSTOM arm of ChannelLayoutTicket.

DolbyVisionConfig

The Dolby Vision decoder configuration record’s two routing seats — the profile number and the base-layer signal-compatibility id — read from the container’s dvcC/dvvC/dwvC box when present.

Ratio

A verbatim AVRational seat.