refactor(mediabunny): [PKG-MB-06] own audio clocks, buffers and context lifecycle

packages/artplayer-proxy-mediabunny/src/audio-clock.ts

@@ -0,0 +1,20 @@
+export interface AudioClock {
+  audioContext: AudioContext | null
+  paused: boolean
+  audioContextStartTime: number
+  playbackTimeAtStart: number
+  playbackRate: number
+}
+
+export function mediaTime(clock: AudioClock): number {
+  if (clock.paused || !clock.audioContext)
+    return clock.playbackTimeAtStart
+  return (clock.audioContext.currentTime - clock.audioContextStartTime) * clock.playbackRate + clock.playbackTimeAtStart
+}
+
+export function bufferTiming(clock: AudioClock, timestamp: number, duration: number, now: number) {
+  const startAt = clock.audioContextStartTime + (timestamp - clock.playbackTimeAtStart) / clock.playbackRate
+  const endAt = startAt + duration / clock.playbackRate
+  const endMediaTime = (endAt - clock.audioContextStartTime) * clock.playbackRate + clock.playbackTimeAtStart
+  return { startAt: Math.max(startAt, now), offset: startAt < now ? (now - startAt) * clock.playbackRate : null, endMediaTime }
+}