@startuml

autonumber

box "Container" #LightGreen
participant Netflix
participant DPI
participant rialtoClient
end box

box "Platform" #LightBlue
participant rialtoServer
participant GStreamer_server
end box

Netflix            ->  DPI:              renderFrame()
DPI                ->  rialtoClient:     renderFrame()
rialtoClient       ->  rialtoServer:     renderFrame()
opt Frame renderable
rialtoServer       ->  GStreamer_server: Trigger rendering of frame

optrialtoServer Frame rendered successfully

note across: It is a Netflix requirement to call updatePlaybackPosition() after--> rialtoClient:     status=true
else renderFrame() called in bad state
rialtoServer       --> rialtoClient:     notifyPosition(position)status=false
end

rialtoClient       --> DPI:              notifyPosition(position)status
DPI                --> Netflix:          updatePlaybackPosition(pts)

rialtoServer       --> rialtoClient:     status=true
else
rialtoServer       --> rialtoClient:     status=false
end

else renderFrame() called in bad state
rialtoServer       --> rialtoClient:     status=false
end

rialtoClient
@enduml

@startuml

autonumber

box "Container" #LightGreen
participant Cobalt
participant Starboard
participant GStreamer_client
participant rialtoClient
end box

box "Platform" #LightBlue
participant rialtoServer
participant GStreamer_server
end box

== Initialisation - register for callbacks ==

opt Video source attached
rialtoServer       ->  GStreamer_server:     g_signal_connect(video_decoder, getVideoUnderflowSignalName_soc(), video_underflow_cb, user_data);

participant GStreamer_server
end box

== Initialisation --> rialtoServer:register for        video_handler_id
endcallbacks ==

opt AudioVideo source attached
rialtoServer       ->  GStreamer_server:     g_signal_connect(audiovideo_decoder, getAudioUnderflowSignalNamegetVideoUnderflowSignalName_soc(), audiovideo_underflow_cb, user_data);
GStreamer_server   --> rialtoServer:         audio_handler_id
end


== Termination - unregister for callbacks ==

opt Video source removed
rialtoServer       ->  GStreamer_server:     g_signal_handler_disconnect(video_decoder, video_handler_id);
GStreamer_server    --> rialtoServer: video_handler_id
end

opt Audio source removedattached
rialtoServer       ->  GStreamer_server:     g_signal_handler_disconnectconnect(audio_decoder, getAudioUnderflowSignalName_soc(), audio_handler_id_underflow_cb, user_data);
GStreamer_server   --> rialtoServer:
end


== Underflow ==

opt Data starvation in server AV pipeline
GStreamer_server   -/  rialtoServer:         video_underflow_cb() or audio_underflow_cb()
rialtoServer       ->  rialtoServer:         Set pipeline state to pausedhandler_id
end


== Termination - unregister for callbacks ==

opt Video source removed
rialtoServer       -/>  rialtoClientGStreamer_server:         notifyPlaybackState(pipeline_session, PLAYBACK_STATE_PAUSED)
rialtoClientg_signal_handler_disconnect(video_decoder, video_handler_id);
GStreamer_server   --> rialtoServer:
end

opt Audio source removed
rialtoServer       -/ > GStreamer_clientserver:     notifyPlaybackState(pipeline_session, PLAYBACK_STATE_PAUSED)
rialtoServer    g_signal_handler_disconnect(audio_decoder, audio_handler_id);
GStreamer_server   --> rialtoServer:
end


== Underflow ==

opt Data starvation in server AV pipeline
GStreamer_server   -/  rialtoClientrialtoServer:         notifyNetworkState(pipeline_session, NETWORK_STATE_STALLED)
rialtoClient       -/  GStreamer_client:     notifyNetworkState(pipeline_session, NETWORK_STATE_STALLED)

note over Starboard, GStreamer_client
Starboard does not have any support for underflow
so the event can be ignored for this integration.
end note

note across
There will be one ore more pending need data requests at this point which if serviced will allow playback to resume
end note

end

== Recovery ==

opt rialtoServer detects that any need media data requests pending at point of underflow are now serviced and pushed to GStreamer_server || EOS signalled for any underflowed sources
note across
It is likely that underflow is due to one source becoming starved whilst data is buffered for other sources, so waiting until pending request(s) are serviced should allow playback to resume.
There are also some YT conformance tests that delay signalling EOS for an underflowed source whilst the other continues to stream hence the EOS condition to allow streaming to resume for the valid source.
end note

rialtoServer       ->  rialtoServer:         Set pipeline state to playing
rialtoServer       -/  rialtoClient:         notifyNetworkState(pipeline_session, NETWORK_STATE_BUFFEREDvideo_underflow_cb() or audio_underflow_cb()
note across
underflow_enabled: Underflow is enabled when we're in playing state and source is attached.
underflow_cancelled: Underflow may be cancelled when haveData is called between notification from GStreamer and Underflow task handling.
end note
opt underflow_enabled && !underflow_cancelled
rialtoServer       -/  rialtoClient:         notifyBufferUnderflow(source_id)
rialtoClient       -/  GStreamer_client:     notifyBufferUnderflow(source_id)
GStreamer_client   -/  Starboard:            emit video_underflow_cb() or audio_underflow_cb()

note over Starboard, GStreamer_client
Starboard does not have any support for underflow
so the event can be ignored for this integration.
end note

end

note across
There will be one re more pending need data requests at this point which if serviced will allow playback to resume
end note

end

@enduml