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fix(goLive): keep IDR in own slot so decoder always has a reference (was blank)

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The tail-drop rewrite let a P-frame supersede a pending keyframe before the
emit tick fired, so the decoder never received an IDR → blank GoLive tile.
Give keyframes their own slot (pendingKey) that P-frames cannot steal, and
only emit a P-frame once at least one IDR has been shown (haveReference).
IDR is always emitted first when present so the reference re-establishes.
This commit is contained in:
asepharyana
2026-08-13 17:43:16 +07:00
parent 8ee32b8df8
commit 7c376ea66a
1 changed files with 33 additions and 21 deletions
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services/discord-gateway/src/goLive/Demuxer.ts
+33 -21
View File
@@ -399,11 +399,15 @@ export async function demux(
opts.frameRate ?? (vInfo.framerate_num / vInfo.framerate_den || 30);
const emitIntervalMs = 1000 / videoFps;
// The single frame we will emit on the next tick. Only the newest survives;
// keyframes are never superseded so the decoder always gets its IDRs.
let latestAu: Buffer | null = null;
let latestIsKey = false;
let skippedFrames = 0; // frames superseded before they could be shown
// The frames we will emit. Keyframes (IDR) get their OWN slot that P-frames
// can never supersede — a missing IDR means the decoder has no reference and
// shows a BLANK tile. P-frames keep only the newest (tail-drop); older ones
// are skipped. A P-frame is only emitted once we have already shown at least
// one keyframe (reference established), otherwise it is dropped.
let pendingKey: Buffer | null = null; // most recent IDR, not yet emitted
let latestP: Buffer | null = null; // newest P-frame, not yet emitted
let haveReference = false; // an IDR has been shown
let skippedFrames = 0; // P-frames superseded/useless before emit
const flushAccessUnit = () => {
if (pendingNals.length === 0) return;
@@ -417,28 +421,36 @@ export async function demux(
pendingNals = [];
pendingHasSlice = false;
pendingIsKey = false;
// Tail-drop: keep only the newest frame. A keyframe always wins (never
// superseded by later non-keys in the same tick window) so the decoder
// keeps getting IDRs; a non-key only replaces a pending non-key.
if (isKey) {
latestAu = au;
latestIsKey = true;
} else if (latestAu === null || latestIsKey) {
latestAu = au;
latestIsKey = false;
// Keyframe: always kept in its own slot, never superseded by a later
// P-frame (that was the previous bug → decoder got no IDR → blank).
pendingKey = au;
} else {
skippedFrames++;
// P-frame: keep only the newest; drop the previous one.
if (latestP !== null) skippedFrames++;
latestP = au;
}
};
// Steady real-time emission clock. Emits the freshest buffered frame once
// per tick (≈ videoFps); never buffers more than one, so no backlog and
// no lag. This — not the encoder rate — defines playback speed.
// Steady real-time emission clock. Emits the freshest frame once per tick
// (≈ videoFps); never buffers more than one of each kind, so no backlog and
// no lag. This — not the encoder rate — defines playback speed. Order: an
// IDR is always emitted first when present so the decoder re-establishes a
// reference; otherwise emit the newest P-frame once a reference exists.
const emitTick = () => {
if (latestAu === null) return;
const au = latestAu;
const isKey = latestIsKey;
latestAu = null;
let au: Buffer | null = null;
let isKey = false;
if (pendingKey !== null) {
au = pendingKey;
isKey = true;
pendingKey = null;
haveReference = true;
} else if (latestP !== null && haveReference) {
au = latestP;
isKey = false;
latestP = null;
}
if (au === null) return;
vPipe.write({
data: au,
// One frame at videoFps: duration=1 in a 1/fps timebase →