4 Messages are refcounted lightweight objects to signal the application
7 Messages are implemented as a subclass of GstMiniObject with a generic
8 GstStructure as the content. This allows for writing custom messages without
9 requiring an API change while allowing a wide range of different types
12 Messages are posted by objects in the pipeline and are passed to the
13 application using the GstBus (See also part-gstbus.txt and part-gstpipeline.txt).
21 Posted by sink elements. This message is posted to the application when
22 all the sinks in a pipeline posted an EOS message. When performing a seek,
23 the EOS state of the pipeline and sinks is undone.
27 An element in the pipeline got into an error state. The message carries
28 a GError and a debug string describing the error. This usually means that
29 part of the pipeline is not streaming anymore.
33 An element in the pipeline encountered a condition that made it produce a
34 warning. This could be a recoverable decoding error or some other non fatal
35 event. The pipeline continues streaming after a warning.
39 An element produced an informational message.
43 An element decoded metadata about the stream. The message carries a GstTagList
44 with the tag information.
46 GST_MESSAGE_BUFFERING:
48 An element is buffering data and that could potentially take some time. This
49 message is typically emited by elements that perform some sort of network
50 buffering. While the pipeline is buffering it should remain in the PAUSED
51 state. When the buffering is finished, it can resume PLAYING.
53 GST_MESSAGE_STATE_CHANGED:
55 An element changed state in the pipeline. The message carries the old, new
56 and pending state of the element.
58 GST_MESSAGE_STATE_DIRTY:
60 An internal message used to instruct a pipeline hierarchy that a state
61 recalculation must be performed because of an ASYNC state change completed.
62 This message is not used anymore.
64 GST_MESSAGE_STEP_DONE:
66 An element stepping frames has finished. This is currently not used.
68 GST_MESSAGE_CLOCK_PROVIDE:
70 An element notifies it capability of providing a clock for the pipeline.
72 GST_MESSAGE_CLOCK_LOST:
74 The current clock as selected by the pipeline became unusable. The pipeline
75 will select a new clock on the next PLAYING state change.
77 GST_MESSAGE_NEW_CLOCK:
79 A new clock was selected for the pipeline.
81 GST_MESSAGE_STRUCTURE_CHANGE:
83 The pipeline changed of structure, This means elements were added or removed or
84 pads were linked or unlinked. This messages is not yet used.
86 GST_MESSAGE_STREAM_STATUS:
88 Posted by an element when it start/stop/pauses a streaming task. It
89 contains information about the reason why the stream state changed along
90 with the thread id. The application can use this information to detect
91 failures in streaming threads. It can also be used to adjust streaming
92 thread priorities by the application.
94 GST_MESSAGE_APPLICATION:
96 The application posted a message. This message must be used when the
97 application posts a message on the bus.
101 Element-specific message, see the specific element's documentation
103 GST_MESSAGE_SEGMENT_START:
105 An element started playback of a new segment. This message is not forwarded
106 the application but is used internally to schedule SEGMENT_DONE messages.
108 GST_MESSAGE_SEGMENT_DONE:
110 An element or bin completed playback of a segment. This message is only posted
111 on the bus if a SEGMENT seek is performed on a pipeline.
113 GST_MESSAGE_DURATION:
115 An element posts this message when it has detected or updated the stream duration.
117 GST_MESSAGE_ASYNC_START:
119 Posted by sinks when they start an asynchronous state change.
121 GST_MESSAGE_ASYNC_DONE:
123 Posted by sinks when they receive the first data buffer and complete the
124 asynchronous state change.
128 Posted by elements when the latency in a pipeline changed and a new global
129 latency should be calculated by the pipeline or application.
131 GST_MESSAGE_REQUEST_STATE:
133 Posted by elements when they want to change the state of the pipeline they
134 are in. A typical use case would be an audio sink that requests the pipeline
135 to pause in order to play a higher priority stream.