@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

== During pipeline creation ==

rialtoServer      ->  GStreamer_server: Subscribe for QOS event

== During playback ==

opt Frames dropped or element changed processing strategy

note across

This event is generate whenever GStreamer generates a QoS event which is currently for these reasons:

 - The element dropped a buffer because of QoS reasons.

 - An element changed its processing strategy because of QoS reasons. This could include a decoder that

   decided to drop every B frame to increase its processing speed or an effect element switching to a lower

   quality algorithm.

end note

GStreamer_server  -/  rialtoServer:     GstBusMessage(qos_event)
rialtoServer      ->  rialtoServer:     Extract required data from event
rialtoServer      -/  rialtoClient:     notifyQos(pipeline_session, source_id, qos_info)
rialtoClient      -/  GStreamer_client: notifyQos(pipeline_session, source_id, qos_info)
GStreamer_client  ->  GStreamer_client: Create GST_EVENT_QOS message from qos_info
GStreamer_client  -/  Starboard:        GST_MESSAGE_QOS(qos_event)

note right
Only number of processed & dropped frames/
samples is sent by Rialto so the QOS event
sent by GStreamer_client will have less
valid properties set than the original server
side event.
end note

note over Cobalt, Starboard
QOS events are not propogated up to
Cobalt but can be queried anytime
by calling SbPlayerInfo2()
end note

end

@enduml