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Original commit message from CVS: * docs/design/part-element-transform.txt: Added some docs about the design of tranform elements. * libs/gst/base/gstbasesrc.c: (gst_base_src_perform_seek), (gst_base_src_loop), (gst_base_src_change_state): Mark buffers with the DISCONT flag.
38 lines
1 KiB
Text
38 lines
1 KiB
Text
Transform elements
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------------------
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Transform elements transform input buffers to output buffers based
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on the sink and source caps.
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typical transform elements include:
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- audio convertors (audioconvert, ...)
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- video convertors (colorspace, videoscale, audioconvert, ...)
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- filters (capfilter, colorbalance,
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The implementation of the transform element has to take care of
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the following things:
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- efficient negotiation both up and downstream
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- efficient buffer alloc and other buffer management
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Some transform elements can operate in different modes:
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- passthrough (no changes to buffers)
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- in-place (changes made to incomming buffer)
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- metadata changes only
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Depending on the mode of operation the buffer allocation strategy might change.
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Negotiation
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-----------
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The transform element is configured to perform a specific transform in these
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two situations:
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- new caps are received on the sink pad.
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- new caps are received on the source pad when allocating an output buffer and
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we can transform to these caps with the current input buffer.
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