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https://github.com/twinksoftware/Gearslip.git
synced 2026-11-10 16:02:25 +01:00
wait for video acks instead of dropping frames
With one frame allowed in flight (LIVI), dropped frames forced keyframe repairs, which caused more drops. LIVI went from 345 forced keyframes a minute to none.
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Seb3thehacker committed
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commit
1adeb6f7e1
1 file changed
+38
-35
@@ -55,9 +55,12 @@ class GearslipRunner(
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@Volatile private var videoStarted = false
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private var videoSource: VideoSource? = null
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@Volatile private var inFlight = 0
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/** Guards [inFlight]: the encoder thread waits on it for the head unit's acks. */
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private val ackLock = Object()
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/** Time the encoder spent waiting for acks since the last stats line. */
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@Volatile private var ackWaitMs = 0L
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@Volatile private var maxUnacked = 4
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@Volatile private var framesSent = 0
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@Volatile private var dropped = 0
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@Volatile private var inputChannelId: Int = -1
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@Volatile private var inputKeycodes: List<Int> = emptyList()
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@Volatile private var sensorChannelId: Int = -1
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@@ -124,6 +127,7 @@ class GearslipRunner(
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fun stop() {
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running = false
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synchronized(ackLock) { ackLock.notifyAll() } // free an encoder waiting on an ack
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videoSource?.stop()
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videoSource = null
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audioLink?.close()
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@@ -700,9 +704,12 @@ class GearslipRunner(
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MSG_MEDIA_ACK -> {
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val fields = Wire.fields(body)
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val acked = Wire.varint(fields, 2)?.toInt() ?: 1
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inFlight = maxOf(0, inFlight - maxOf(1, acked))
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acksSeen++
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lastAckAt = System.currentTimeMillis()
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synchronized(ackLock) {
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inFlight = maxOf(0, inFlight - maxOf(1, acked))
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acksSeen++
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lastAckAt = System.currentTimeMillis()
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ackLock.notifyAll()
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}
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if (framesSent <= 3 || framesSent % 60 == 0) {
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log.i("<- MediaAck(ack=$acked) inFlight=$inFlight after $framesSent frames")
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}
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@@ -784,39 +791,31 @@ class GearslipRunner(
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}
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}
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/**
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* Flow control: the head unit allows max_unacked frames in flight (LIVI allows one). When
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* the window is full this waits for an ack instead of dropping the frame. A dropped frame
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* breaks the decoder's chain, so it cost a keyframe to repair; keyframes are twenty times
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* the size, so they caused more drops, and the stream sank into a storm of them (345 in a
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* minute on LIVI, at 5-12 fps). Waiting here holds the encoder back instead, which simply
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* makes it produce fewer frames, each one whole.
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*/
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private fun sendVideoFrame(data: ByteArray, presentationTimeUs: Long, keyFrame: Boolean) {
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// Flow control: the head unit told us max_unacked in its Config reply.
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if (inFlight >= maxUnacked) {
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// A dropped or never-sent ack would otherwise wedge the stream forever, which
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// looks identical to a frozen picture. Assume the window cleared and carry on.
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val since = System.currentTimeMillis() - lastAckAt
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if (since > ACK_STALL_MS) {
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log.w("no ack for ${since}ms with $inFlight in flight - resetting the window")
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inFlight = 0
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} else {
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dropped++
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if (dropped % 30 == 1) {
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log.w("dropping frame - $inFlight in flight (max $maxUnacked)")
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synchronized(ackLock) {
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val waitStart = System.currentTimeMillis()
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while (running && inFlight >= maxUnacked) {
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// A lost ack would otherwise hold the stream forever, which looks like a frozen
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// picture. After a long silence, assume the window cleared and carry on.
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val since = System.currentTimeMillis() - lastAckAt
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if (since > ACK_STALL_MS) {
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log.w("no ack for ${since}ms with $inFlight in flight - resetting the window")
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inFlight = 0
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break
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}
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// A dropped frame breaks the decoder's reference chain on the head unit -
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// every frame after it is a P-frame assuming a picture that never arrived.
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// Without a resync the picture free-runs on corrupted state indefinitely,
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// which is the smeared/ghosted look.
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//
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// Ask on EVERY drop, not just the first in a streak: the resync keyframe we
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// asked for is itself just another frame, and can be dropped by this exact
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// same check. A one-shot request that gets swallowed by the burst that
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// provoked it leaves the stream corrupted for good, with no further request
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// ever made - confirmed on the road (docs/spike/phase-c-stuck-resync-2026-09-17.log,
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// dropped=27 in one burst, video dead at 0fps for 100+s afterward). Repeated
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// setParameters(REQUEST_SYNC_FRAME) calls before one lands are harmless - it
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// just keeps the "next frame is a keyframe" flag set.
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resyncRequested = true
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resyncAttempts++
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videoSource?.requestSyncFrame()
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return
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ackLock.wait(ACK_STALL_MS - since + 1)
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}
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ackWaitMs += System.currentTimeMillis() - waitStart
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}
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if (!running) return
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val timestamp = ByteArray(8)
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for (i in 0 until 8) {
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timestamp[i] = ((presentationTimeUs shr ((7 - i) * 8)) and 0xFF).toByte()
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@@ -972,9 +971,13 @@ class GearslipRunner(
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val sent = framesSent
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val fps = (sent - lastFrames) / 5.0
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lastFrames = sent
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SessionReport.stream("${"%.1f".format(fps)} fps, sent=$sent dropped=$dropped acked=$acksSeen")
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// Time the encoder spent held back waiting for acks: near 5000ms means the
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// head unit's acks, not the phone, set the frame rate.
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val waited = ackWaitMs
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ackWaitMs = 0
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SessionReport.stream("${"%.1f".format(fps)} fps, sent=$sent acked=$acksSeen")
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log.i(
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"video: ${"%.1f".format(fps)} fps over 5s | sent=$sent dropped=$dropped " +
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"video: ${"%.1f".format(fps)} fps over 5s | sent=$sent waited=${waited}ms " +
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"acked=$acksSeen inFlight=$inFlight split=$splitMessages",
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)
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