2016-12-08 22:58:08 +00:00
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# playbin
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The purpose of this element is to decode and render the media contained
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2016-12-19 22:04:31 +00:00
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in a given generic uri. The element extends `GstPipeline` and is typically
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2016-12-08 22:58:08 +00:00
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used in playback situations.
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Required features:
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- accept and play any valid uri. This includes
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- rendering video/audio
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- overlaying subtitles on the video
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- optionally read external subtitle files
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- allow for hardware (non raw) sinks
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- selection of audio/video/subtitle streams based on language.
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- perform network buffering/incremental download
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- gapless playback
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- support for visualisations with configurable sizes
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- ability to reject files that are too big, or of a format that would
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require too much CPU/memory usage.
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- be very efficient with adding elements such as converters to reduce
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the amount of negotiation that has to happen.
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- handle chained oggs. This includes having support for dynamic pad
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add and remove from a demuxer.
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## Components
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### decodebin
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- performs the autoplugging of demuxers/decoders
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- emits signals when for steering the autoplugging
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- to decide if a non-raw media format is acceptable as output
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- to sort the possible decoders for a non-raw format
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- see also decodebin2 design doc
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### uridecodebin
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- combination of a source to handle the given uri, an optional
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queueing element and one or more decodebin2 elements to decode the
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non-raw streams.
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### playsink
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- handles display of audio/video/text.
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- has request audio/video/text input pad. There is only one sinkpad
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per type. The requested pads define the configuration of the
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internal pipeline.
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- allows for setting audio/video sinks or does automatic
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sink selection.
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- allows for configuration of visualisation element.
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- allows for enable/disable of visualisation, audio and video.
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### playbin
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- combination of one or more uridecodebin elements to read the uri and
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subtitle uri.
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- support for queuing new media to support gapless playback.
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- handles stream selection.
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- uses playsink to display.
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- selection of sinks and configuration of uridecodebin with raw
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output formats.
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## Gapless playback feature
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playbin has an "about-to-finish" signal. The application should
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configure a new uri (and optional suburi) in the callback. When the
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current media finishes, this new media will be played next.
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