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Original commit message from CVS: * docs/design/part-events.txt: * docs/design/part-gstbus.txt: * docs/design/part-gstpipeline.txt: * docs/design/part-messages.txt: * docs/design/part-overview.txt: * docs/design/part-segments.txt: * gst/gstbin.c: * gst/gstbuffer.c: * gst/gstclock.c: * gst/gstelement.c: * gst/gstevent.c: * gst/gstfilter.c: * gst/gstiterator.c: Various documentation updates.
87 lines
2.4 KiB
Plaintext
87 lines
2.4 KiB
Plaintext
Messages
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--------
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Messages are refcounted lightweight objects to signal the application
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of pipeline events.
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Messages are implemented as a subclass of GstMiniObject with a generic
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GstStructure as the content. This allows for writing custom messages without
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requiring an API change while allowing a wide range of different types
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of messages.
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Messages are posted by objects in the pipeline and are passed to the
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application using the GstBus.
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Message types
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-------------
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GST_MESSAGE_EOS:
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The pipeline went to EOS. This means that all the sink elements in the
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pipeline posted the EOS message to the bus.
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GST_MESSAGE_ERROR:
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An element in the pipeline got into an error state. The message carries
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a GError and a debug string describing the error. This usually means that
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part of the pipeline is not streaming anymore.
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GST_MESSAGE_WARNING:
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An element in the pipeline encountered a condition that made it produce a
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warning. This could be a recoverable decoding error or some other non fatal
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event. The pipeline continues streaming after a warning.
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GST_MESSAGE_INFO:
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An element produced an informational message.
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GST_MESSAGE_TAG:
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An element decoded metadata about the stream. The message carries a GstTagList
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with the tag information.
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GST_MESSAGE_BUFFERING:
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An element is buffering data and that could potentially take some time.
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GST_MESSAGE_STATE_CHANGED:
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An element changed state in the pipeline. The message carries the old an new
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state of the element.
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GST_MESSAGE_STEP_DONE:
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An element stepping frames has finished.
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GST_MESSAGE_NEW_CLOCK:
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A new clock was selected for the pipeline.
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GST_MESSAGE_STRUCTURE_CHANGE:
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The pipeline changed of structure, This means elements were added or removed or
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pads were linked or unlinked.
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GST_MESSAGE_STREAM_STATUS:
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An element posted information about the stream it is handling. This could include
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information about the length of the stream.
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GST_MESSAGE_APPLICATION:
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An element posted an application specific message.
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GST_MESSAGE_SEGMENT_START:
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An element started playback of a new segment. This message is not forwarded
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the the application but is used internally to scheduler SEGMENT_DONE messages.
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GST_MESSAGE_SEGMENT_DONE:
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An element or bin completed playback of a segment. This message is only posted
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on the bus if a SEGMENT seek is performed on a pipeline.
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