[Bug 706340] videofilter: it might make sense to implement the "transform_meta" virtual method

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=706340
  GStreamer | gst-plugins-base | git

Wim Taymans <wim.taymans> changed:

           What    |Removed                     |Added
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                 CC|                            |wim.taymans at gmail.com

--- Comment #4 from Wim Taymans <wim.taymans at gmail.com> 2013-08-20 13:18:49 UTC ---
(In reply to comment #3)
> The tags with which you register a meta tell you on which aspects of a buffer
> this meta applies. That can be used to generically handle unknown metas to some
> degree.

That's the idea, the tags themselves are not very well defined but we currently
have:

- memory: metadata describes memory layout and size etc, if memory layout
changes, metadata becomes invalid

- colorspace: metadata describes colorspace, if colorspace changes, metadata
needs to be removed. videoconvert removes this meta when it does a transform

- size: metadata is related to video size, if the size changes, remove meta

There are also transform functions defined for, for example, scaling. A
metadata that depends on the size can implement a scale transform and update
the metadata accordingly. A filter that changes the size needs to either remove
all size dependent metadata or call the transform with the scale quark and
extra info.

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