score::gfx::ExternalGenlockClock Class Reference

Hardware-genlock render clock (opt-in): a card's output VBI. More...

Inheritance diagram for score::gfx::ExternalGenlockClock:

Detailed Description

Hardware-genlock render clock (opt-in): a card's output VBI.

The pull facet of the model. A dedicated tick thread blocks on an injected waitForNextTick (the card's WaitForOutputVerticalInterrupt for AJA, VHD_WaitSlotSent for Deltacast, ...) and, on each hardware tick, marshals the render callback onto owner's thread — score's render thread — via a blocking queued invoke (Qt::BlockingQueuedConnection). Blocking is deliberate: the next VBI wait only begins once the current frame has finished rendering, so render stays phase-locked to the card genlock and never bursts ahead of it. This is exactly how PacedFramePump marshals the submit side.

The pull facet is injected (a std::function) so this class carries no vendor SDK dependency — the AJA backend supplies its VBI wait, gfx stays SDK-free.

Contention note: the injected wait is generally a SECOND waiter on the same output VBI the submit pump already waits on. On the Linux AJA driver the VBI is a broadcast wait-queue (every waiter wakes per interrupt), so two waiters is safe; validate on any platform where the tick is an auto-reset event.

Thread-affinity contract for stop(): call it on owner's thread (or with that thread's event loop running). The tick thread may be parked in the blocking invoke waiting for the owner to run the functor; stop() pumps the owner's event queue so that in-flight invoke drains instead of dead-locking the join.

Public Member Functions
	ExternalGenlockClock (QObject *owner, std::function< bool()> waitForNextTick)
Kind	kind () const noexcept override
void	start (std::function< void()> tick) override
	Begin delivering ticks.
void	stop () override
	Stop delivering ticks and release the underlying tick source.

Additional Inherited Members
Public Types inherited from score::gfx::RenderClock
enum class	Kind { Timer , DisplayVSync , ExternalGenlock }

Constructor & Destructor Documentation

ExternalGenlockClock()

score::gfx::ExternalGenlockClock::ExternalGenlockClock	(	QObject *	owner,
		std::function< bool()>	waitForNextTick
	)

Parameters

owner	QObject whose thread the render tick must run on (score's render thread).
waitForNextTick	blocking pull facet: returns true when a hardware tick (VBI) arrived, false on timeout (the loop re-checks running so stop() stays responsive).

Member Function Documentation

kind()

Kind score::gfx::ExternalGenlockClock::kind ( ) const

inlineoverridevirtualnoexcept

Implements score::gfx::RenderClock.

start()

void score::gfx::ExternalGenlockClock::start ( std::function< void()>  tick )

overridevirtual

Begin delivering ticks.

tick is invoked once per render tick, on the render thread. The clock owns the tick source (timer, vsync registration, or hardware wait loop).

Implements score::gfx::RenderClock.

stop()

void score::gfx::ExternalGenlockClock::stop ( )

overridevirtual

Stop delivering ticks and release the underlying tick source.

Implements score::gfx::RenderClock.

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The documentation for this class was generated from the following files:

• RenderClock.hpp
• RenderClock.cpp