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async state change & pad flags example
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Artem Martus
232
examples/plugins/async-identity/asyncidentity.go
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232
examples/plugins/async-identity/asyncidentity.go
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//lint:file-ignore U1000 Ignore all unused code, this is example code
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// +plugin:Name=async-identity
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// +plugin:Description=A go-gst example plugin with async state changes
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// +plugin:Version=v0.0.1
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// +plugin:License=gst.LicenseLGPL
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// +plugin:Source=go-gst
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// +plugin:Package=examples
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// +plugin:Origin=https://github.com/go-gst/go-gst
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// +plugin:ReleaseDate=2024-09-13
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//
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// +element:Name=asyncidentity
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// +element:Rank=gst.RankNone
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// +element:Impl=asyncidentity
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// +element:Subclass=gst.ExtendsElement
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//
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//go:generate gst-plugin-gen
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package main
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import (
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"fmt"
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"sync/atomic"
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"time"
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"github.com/go-gst/go-glib/glib"
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"github.com/go-gst/go-gst/gst"
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)
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var (
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_cat = gst.NewDebugCategory(
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"asyncidentity",
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gst.DebugColorNone,
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"asyncidentity element",
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)
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_srcPadTemplate = gst.NewPadTemplate("generic-src", gst.PadDirectionSource,
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gst.PadPresenceAlways, gst.NewAnyCaps())
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_sinkPadTemplate = gst.NewPadTemplate("generic-sink", gst.PadDirectionSink,
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gst.PadPresenceAlways, gst.NewAnyCaps())
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_properties = []*glib.ParamSpec{
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glib.NewUint64Param(
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"delay",
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"ns state change delay",
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"Duration in nanoseconds to wait until a state changes",
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_delayNsMin, _delayNsMax, _delayNsDefault,
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glib.ParameterReadWrite,
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),
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}
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)
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const (
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_propDelayNs = 0
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_delayNsMin = uint64(0)
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_delayNsMax = uint64(time.Second) * 10
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_delayNsDefault = uint64(time.Second)
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)
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func main() {}
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type asyncidentity struct {
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// inner state
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sinkpad *gst.Pad
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srcpad *gst.Pad
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asyncPending atomic.Bool
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// property storage
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delayNs atomic.Uint64
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}
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var _ glib.GoObjectSubclass = (*asyncidentity)(nil)
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func (g *asyncidentity) New() glib.GoObjectSubclass { return &asyncidentity{} }
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func (g *asyncidentity) ClassInit(klass *glib.ObjectClass) {
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class := gst.ToElementClass(klass)
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class.SetMetadata(
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"Async Identity Example",
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"General",
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"An async state changing identity like element",
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"Artem Martus <artemmartus2012@gmail.com>",
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)
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class.AddStaticPadTemplate(_srcPadTemplate)
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class.AddStaticPadTemplate(_sinkPadTemplate)
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class.InstallProperties(_properties)
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}
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var _ glib.GoObject = (*asyncidentity)(nil)
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func (g *asyncidentity) SetProperty(obj *glib.Object, id uint, value *glib.Value) {
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self := gst.ToElement(obj)
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switch id {
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case _propDelayNs:
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newDelayErased, err := value.GoValue()
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if err != nil {
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self.Error("Failed unmarshalling the 'delay' property", err)
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return
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}
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newDelay, ok := newDelayErased.(uint64)
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if !ok {
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self.Error("Failed Go-casting the 'delay' interface{} into uint64",
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fmt.Errorf("interfaced value: %+v", newDelayErased))
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return
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}
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oldDelay := g.delayNs.Swap(newDelay)
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self.Log(_cat, gst.LevelInfo,
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fmt.Sprintf("Changed delay property %s => %s",
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time.Duration(oldDelay),
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time.Duration(newDelay),
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))
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default:
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self.Error("Tried to set unknown property",
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fmt.Errorf("prop id %d: %s", id, value.TypeName()))
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}
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}
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func (g *asyncidentity) GetProperty(obj *glib.Object, id uint) *glib.Value {
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var (
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out *glib.Value
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err error
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)
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switch id {
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case _propDelayNs:
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out, err = glib.GValue(g.delayNs.Load())
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default:
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err = fmt.Errorf("unknown property id: %d", id)
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}
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if err != nil {
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self := gst.ToElement(obj)
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self.Error("Get property error", err)
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out = nil
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}
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return out
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}
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func (g *asyncidentity) Constructed(self *glib.Object) {
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elem := gst.ToElement(self)
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srcPad := gst.NewPadFromTemplate(_srcPadTemplate, "src")
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sinkPad := gst.NewPadFromTemplate(_sinkPadTemplate, "sink")
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sinkPad.SetChainFunction(g.sink_chain_function)
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// Have to set proxy flags on a pads
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proxyFlags := gst.PadFlagProxyAllocation | gst.PadFlagProxyCaps | gst.PadFlagProxyScheduling
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sinkPad.SetFlags(proxyFlags)
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srcPad.SetFlags(proxyFlags)
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// Or setup query & event functions like so
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// sinkPad.SetQueryFunction(func(self *gst.Pad, parent *gst.Object, query *gst.Query) bool {
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// return srcPad.PeerQuery(query)
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// })
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// sinkPad.SetEventFunction(func(self *gst.Pad, parent *gst.Object, event *gst.Event) bool {
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// return srcPad.PushEvent(event)
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// })
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// srcPad.SetQueryFunction(func(self *gst.Pad, parent *gst.Object, query *gst.Query) bool {
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// return sinkPad.PeerQuery(query)
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// })
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// srcPad.SetEventFunction(func(self *gst.Pad, parent *gst.Object, event *gst.Event) bool {
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// return sinkPad.PushEvent(event)
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// })
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elem.AddPad(srcPad)
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elem.AddPad(sinkPad)
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g.srcpad = srcPad
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g.sinkpad = sinkPad
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g.delayNs.Store(_delayNsDefault)
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}
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func (g *asyncidentity) sink_chain_function(
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_self *gst.Pad,
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_parent *gst.Object,
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buffer *gst.Buffer,
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) gst.FlowReturn {
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return g.srcpad.Push(buffer)
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}
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// var _ gst.ElementImpl = (*asyncidentity)(nil)
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func (g *asyncidentity) ChangeState(el *gst.Element, transition gst.StateChange) gst.StateChangeReturn {
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if ret := el.ParentChangeState(transition); ret == gst.StateChangeFailure {
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return ret
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}
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switch transition {
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case gst.StateChangeNullToReady:
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// async will be ignored due to target state <= READY
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case gst.StateChangeReadyToPaused:
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// async will be ignored due to no_preroll
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return gst.StateChangeNoPreroll
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case gst.StateChangePausedToPlaying:
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fallthrough
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case gst.StateChangePlayingToPaused:
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g.asyncStateChange(el)
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return gst.StateChangeAsync
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case gst.StateChangePausedToReady:
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// async will be ignored due to target state <= READY
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case gst.StateChangeReadyToNull:
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}
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// check against forcing state change
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if g.asyncPending.Load() {
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return gst.StateChangeAsync
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}
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return gst.StateChangeSuccess
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}
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func (g *asyncidentity) asyncStateChange(el *gst.Element) {
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msg := gst.NewAsyncStartMessage(el)
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_ = el.PostMessage(msg)
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go func(el *gst.Element) {
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g.asyncPending.Store(true)
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delay := time.Duration(g.delayNs.Load())
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<-time.After(delay)
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msg := gst.NewAsyncDoneMessage(el, gst.ClockTimeNone)
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_ = el.PostMessage(msg)
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g.asyncPending.Store(false)
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}(el)
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}
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