@seydx/rtsp

Appearance

@seydx/rtsp / RawAudioTranscoder

Class: RawAudioTranscoder ​

Defined in: sources/raw-audio-transcoder.ts:264

Normalizes raw framed elementary audio into a demuxable stream.

Some devices deliver audio as bare coded frames with no container at all — the canonical case is raw AAC-ELD, whose frames cannot be expressed in ADTS and therefore break every ADTS-based consumer. This class accepts those frames one push() at a time, decodes them (optionally with an explicit decoder such as libfdk_aac), re-encodes to a standards-compliant target (AAC-LC in ADTS by default), and exposes the result as a Readable that plugs directly into an AvSource or MultiSource input.

Example ​

typescript
import { buildAacEldConfig, MultiSource, RawAudioTranscoder } from '@seydx/rtsp';

// Raw AAC-ELD: 16 kHz mono, 480-sample frames, decodable only via libfdk.
const audio = new RawAudioTranscoder({
  from: { codec: 'aac', decoder: 'libfdk_aac', sampleRate: 16000, channels: 1, samplesPerFrame: 480, config: buildAacEldConfig(16000, 1, 480) },
  to: { bitRate: 32000 },
});
await audio.start();
audioFrameStream.on('data', (frame) => audio.push(frame));

const source = new MultiSource([
  { input: videoStream, format: 'h264' },
  { input: audio.stream, format: 'aac' },
]);

See ​

Constructors ​

Constructor ​

new RawAudioTranscoder(options): RawAudioTranscoder

Defined in: sources/raw-audio-transcoder.ts:288

Create a raw audio transcoder.

The transcoder is inert until RawAudioTranscoder.start is called; the constructor only captures configuration.

Parameters ​

options ​

RawAudioTranscoderOptions

Input format, target format, and tuning.

Returns ​

RawAudioTranscoder

Accessors ​

stream ​

Get Signature ​

get stream(): Readable

Defined in: sources/raw-audio-transcoder.ts:302

The transcoded output as a readable byte stream.

Emits the target container bytes (ADTS by default) as they are produced. Hand this to an AvSource/MultiSource input; it ends when the transcoder is closed.

Example ​
typescript
const inputs = [{ input: transcoder.stream, format: 'aac' }];
Returns ​

Readable

Methods ​

close() ​

close(): Promise<void>

Defined in: sources/raw-audio-transcoder.ts:481

Stop the transcoder and release all pipeline resources.

Interrupts the blocked demuxer read so the background loop can unwind, waits for it, then closes every stage and ends the output stream. Safe to call when the transcoder was never started or is already closed.

Returns ​

Promise<void>

Resolves once all resources are released.

Example ​

typescript
await transcoder.close();

push() ​

push(frame): void

Defined in: sources/raw-audio-transcoder.ts:460

Feed one complete coded audio frame into the pipeline.

The buffer must contain exactly one frame in the configured input format; partial or concatenated frames are undecodable for raw elementary codecs. Calling push before RawAudioTranscoder.start (or after RawAudioTranscoder.close) is a silent no-op.

Parameters ​

frame ​

Buffer

One coded audio frame.

Returns ​

void

Example ​

typescript
audioSource.on('data', (frame) => transcoder.push(frame));

start() ​

start(): Promise<void>

Defined in: sources/raw-audio-transcoder.ts:324

Start the transcode pipeline.

Resolves the decoder and encoder, announces the input format to the demuxer via a synthetic SDP (including the codec config when given), and wires up the decode, resample, encode, and mux stages. Calling start when already active is a no-op.

Returns ​

Promise<void>

Resolves once the pipeline is running.

Throws ​

If the input decoder or target encoder cannot be resolved, or the synthetic SDP contains no audio stream.

Example ​

typescript
await transcoder.start();