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72 lines
2.7 KiB
Text
72 lines
2.7 KiB
Text
The avi decoder plugins
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-----------------------
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The avi decoder consists of a set of gstreamer plugins:
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- demuxer (avidemux)
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- avi to gstreamer type converter (avitypes)
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- windows dlls wrappers.
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the avidecoder element uses the above plugins to perform the avi
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decoding. It is constructed as a custom bin which initially only has
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the demuxer element in it. The demuxer has a set of padtemplates for
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raw audio and video.
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(------------------------------------)
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! avidecoder !
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! (video/raw)...
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! (----------) !
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! ! demuxer (video/avi, auds).. !
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! ! ! !
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! -src ! !
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! / ! (video/avi, vids).. !
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- src ! ! !
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! (----------) (audio/raw)...
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! !
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(------------------------------------)
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the demuxer has a set of padtemplates for the raw avi header properties.
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The avi decoder will act on the new_pad signal of the demuxer element
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and will attach an avitype plugin to the new pad. Caps negotiation will
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convert the raw avi caps to the gstreamer caps. If the src pad of the
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avitypes plugin are compatible with the avidecoder padtemplate, the
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avitype pad is ghosted to the avidecoder bin, this is the case where no
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codec is needed (for raw PCM samples, for example).
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When the avitypes caps are not compatible with one of the avidecoder
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templates, a static autoplugger is used the find an element to connect
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the demuxers pad to the decoders padtemplate.
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When no element could be found, an windec plugin is attached to the
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demuxers pad and the avitypes plugin is removed from the decoder.
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example:
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--------
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An avidecoder that has a video pad (decoded with windows dlls) and an
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audio pad (raw PCM).
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(----------------------------------------------------------------)
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! avidecoder (--------) (------) !
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! !avitypes! !windec! /-- (video/raw)
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! (----------) /-sink src--sink src ----- !
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! !demuxer (video/avi, ! ! ! ! !
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! ! ! auds).. (--------) (------) !
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! -sink ! (--------) !
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! / ! (video/avi, !avitypes! !
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-sink ! ! vids).. ! ! !
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! (----------) \-sink src -------------------- (audio/raw)
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! (--------) !
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(----------------------------------------------------------------)
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TODO
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----
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automatically generate the padtemplates from all possible avi types
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found in the registry.
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