Enum Gst.StateChange
The element must check if the resources it needs are available. Device sinks and -sources typically try to probe the device to constrain their caps. The element opens the device (in case feature need to be probed). The element pads are activated in order to receive data in PAUSED. Streaming threads are started. Some elements might need to return ASYNC and complete the state change when they have enough information. It is a requirement for sinks to return ASYNC and complete the state change when they receive the first buffer or EOS event (preroll). Sinks also block the dataflow when in PAUSED. A pipeline resets the running_time to 0. Live sources return NO_PREROLL and don't generate data. Most elements ignore this state change. The pipeline selects a clock and distributes this to all the children before setting them to PLAYING. This means that it is only alowed to synchronize on the clock in the PLAYING state. The pipeline uses the clock and the running_time to calculate the base_time. The base_time is distributed to all children when performing the state change. Sink elements stop blocking on the preroll buffer or event and start rendering the data. Sinks can post the EOS message in the PLAYING state. It is not allowed to post EOS when not in the PLAYING state. While streaming in PAUSED or PLAYING elements can create and remove sometimes pads. Live sources start generating data and return SUCCESS. Most elements ignore this state change. The pipeline calculates the running_time based on the last selected clock and the base_time. It stores this information to continue playback when going back to the PLAYING state. Sinks unblock any clock wait calls. When a sink does not have a pending buffer to play, it returns ASYNC from this state change and completes the state change when it receives a new buffer or an EOS event. Any queued EOS messages are removed since they will be reposted when going back to the PLAYING state. The EOS messages are queued in GstBins. Live sources stop generating data and return NO_PREROLL. Sinks unblock any waits in the preroll. Elements unblock any waits on devices Chain or get_range functions return WRONG_STATE. The element pads are deactivated so that streaming becomes impossible and all streaming threads are stopped. The sink forgets all negotiated formats Elements remove all sometimes pads Elements close devices Elements reset any internal state. These are the different state changes an element goes through.
GST_STATE_NULL ⇒
GST_STATE_PLAYING is called an upwards state change and
GST_STATE_PLAYING ⇒
GST_STATE_NULL a downwards state change.
Values
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Number Gst.StateChange. NULL_TO_READY : 10
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Number Gst.StateChange. PAUSED_TO_PLAYING : 28
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Number Gst.StateChange. PAUSED_TO_READY : 26
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Number Gst.StateChange. PLAYING_TO_PAUSED : 35
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Number Gst.StateChange. READY_TO_NULL : 17
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Number Gst.StateChange. READY_TO_PAUSED : 19
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Used by These Methods / Signals / Properties
Gst.Element
Method
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Perform transition on element.
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