daniel-c-harvey
47 lines
2.1 KiB
TypeScript
47 lines
2.1 KiB
TypeScript
/**
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* OpusCapability - runtime detection of WebCodecs Ogg-Opus decode support.
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*
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* The Opus decode path is a WebCodecs `AudioDecoder` streaming pipeline (OpusStreamDecoder), NOT
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* `decodeAudioData`. So the capability gate must test the path actually used: whether the browser has
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* `AudioDecoder` AND supports the `codec: 'opus'` config. `AudioDecoder` is available on Chrome/Edge,
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* Firefox 130+, and Safari 16.4+; older Safari and older Firefox lack it, and those listeners fall back
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* to the universal lossless WAV path (§3.4 / OQ2 / AC7 — no listener ever gets silence over a codec gap).
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*
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* This module is the detection *seam* only — it answers "can this browser stream-decode Opus via
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* WebCodecs?". The player (StreamingAudioPlayerService.ResolveStreamFormatAsync) consumes the answer to
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* choose the delivery format; this module never touches the player or the stream request. The result is
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* cached after the first probe (capability does not change within a session).
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*/
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let cachedSupport: Promise<boolean> | null = null;
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/**
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* Resolve whether this browser can stream-decode Ogg Opus via WebCodecs. Cached after the first call.
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* Never rejects — any failure (no AudioDecoder, unsupported config, thrown probe) resolves to `false`
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* (treat as unsupported, fall back to lossless) so an interop error can never silence playback.
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*/
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export function canDecodeOggOpus(): Promise<boolean> {
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if (cachedSupport === null) {
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cachedSupport = probe();
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}
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return cachedSupport;
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}
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async function probe(): Promise<boolean> {
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try {
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if (typeof AudioDecoder === 'undefined' || typeof AudioDecoder.isConfigSupported !== 'function') {
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return false;
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}
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// 48 kHz stereo is the canonical fullband Opus shape this site produces. isConfigSupported does
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// not need the OpusHead `description` to report codec support, so we probe without it.
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const result = await AudioDecoder.isConfigSupported({
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codec: 'opus',
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sampleRate: 48000,
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numberOfChannels: 2
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});
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return result.supported === true;
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} catch {
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return false;
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}
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}
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