lib/decode-gate

What a decoder should do with each frame that arrives, so a decoder that falls behind costs the stream as little as possible.

A decoder given more than it can decode has to let something go, and what it lets go breaks the frames that predict from it. Where the encoder says what each frame predicts from, the cheapest repair is to drop the frame, tell the server which one went, and hold back only what predicts from it: the encoder predicts past it and decoding resumes on its next frame, no key frame on the wire. Where the encoder says nothing -- a stripe of a striped stream, a codec whose session does not track its references -- the only repair is a key frame, so the gate asks for one instead. A run of drops that the encoder never predicts past is the same case and ends in that request too.

Classes

DecodeGate

Defined in: lib/decode-gate.js:40

Constructors

Constructor

new DecodeGate(options?): DecodeGate;

Defined in: lib/decode-gate.js:45

Parameters

Parameter	Type	Description
`options?`	{ `now?`: () => `number`; }	-
`options.now?`	() => `number`	Monotonic clock in ms.

Returns

DecodeGate

Methods

configured()

configured(): void;

Defined in: lib/decode-gate.js:55

The decoder was (re)built, so it needs a key frame before anything else.

Returns

void

invalidated()

invalidated(): void;

Defined in: lib/decode-gate.js:62

Nothing decoded so far is usable, so only a key frame is.

Returns

void

decide()

decide(
   key, 
   frameId, 
   reference, 
   queueSize
): Decision;

Defined in: lib/decode-gate.js:80

Parameters

Parameter	Type	Description
`key`	`boolean`	Whether the frame decodes on its own.
`frameId`	`number`	The frame's own id.
`reference`	`number`	The id of the frame it predicts from; its own id, or undefined, where the encoder does not say.
`queueSize`	`number`	Frames the decoder has yet to decode.

Returns

Decision

Type Aliases

Decision

type Decision = "decode" | "lost" | "no_key" | "overload";

Defined in: lib/decode-gate.js:35

What to do with a frame: decode it, let it go and report it lost, or ask for a key frame because none has been decoded yet or because dropping more would not help.