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Original commit message from CVS: * docs/design/draft-klass.txt: * docs/design/part-clocks.txt: * docs/design/part-events.txt: * docs/design/part-gstbin.txt: * docs/design/part-gstpipeline.txt: * docs/design/part-messages.txt: * docs/design/part-negotiation.txt: * docs/design/part-overview.txt: * docs/design/part-preroll.txt: * docs/design/part-seeking.txt: * docs/design/part-states.txt: * docs/design/part-streams.txt: Documentation updates.
104 lines
3.1 KiB
Plaintext
104 lines
3.1 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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Posted by sink elements. This message is posted to the application when
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all the sinks in a pipeline posted an EOS message. When performing a seek,
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the EOS state of the pipeline and sinks is undone.
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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. This
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message is typically emited by elements that perform some sort of network
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buffering. While the pipeline is buffering it should remain in the PAUSED
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state. When the buffering is finished, it can resume PLAYING.
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GST_MESSAGE_STATE_CHANGED:
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An element changed state in the pipeline. The message carries the old, new
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and pending 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_CLOCK_PROVIDE:
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An element notifies it capability of providing a clock for the pipeline.
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GST_MESSAGE_CLOCK_LOST:
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The current clock as selected by the pipeline became unusable. The pipeline
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will select a new clock on the next PLAYING state change.
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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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The application posted a message.
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GST_MESSAGE_ELEMENT:
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Element-specific message, see the specific element's documentation
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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 schedule 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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