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Edward Hervey 2011-01-18 20:03:42 +01:00
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54
docs/design/effects.txt
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@ -12,41 +12,45 @@ Summary
4. Use-cases
5. API draft
The goal of this proposal is to find a simple way to handle effects through an
API which would allow developers to handle any use-case
The goal of this proposal is to design a simple way to handle effects through an
API which would allow developers to handle any use-cases.
1. Basic ideas
----------------
* Effects are actually descendant of GESTrackOperation
* GESTrackEffects are subclasses of GESTrackOperation
* You can add effects on any clip or layer
* You can add effects between several clips and control them as a unique effect.
* You can add effects over several clips and control them as a unique effect.
* Effects are configurable and those could change during time
* Effects are configurable and those properties can change during time
* We should be able to handle the gnome-video-effects standard. We should also offer
a system to be able to handle any other effect system.
* We must be able to handle third-party effect providers, like the
gnome-video-effects standard.
* We can implement complexe effects. It means effects that are more
* We must be able to implement complex effects. This means effects that are more
than adding GstElement-s to the timeline. It can also mean effects
that are both: video and audio at the same time
that apply both video and audio changes.
2. Problems
----------
* We should be able to handle list of available effects on the system at
* We must be able to provide a list of effects available on the system at
runtime.
* We should be able to configure effects through an API in GES and
* We must be able to configure effects through an API in GES and
not directly configuring the corresponding GstElement properties.
==> EDWARD : The wording makes it a bit confusing. Here one could
read that we'll be offering an API to get/change properties
which is completely different from the standard GObject API.
* We should also expose the GstElement-s contained in an effect so
it is possible for people to control their properties as they wish.
* We should be able to implement and handle complexe effects directly in GES
* We must be able to implement and handle complexe effects directly in GES
* We should be able to configure effects in the time -> Keyframes without
* We must be able to configure effects through time -> Keyframes without
duplicating code from GStreamer
@ -67,11 +71,12 @@ B. Effects configurability
The idea to be able to configure effects through a simple API in GES would
be to add an API in GESTrackObject to access the gst-object properties that
user would like to configure.
We would also have a method to set those properties easily
We would also have a method to set those properties easily.
We should also find a way to handle that in thecase of systems such as gnome-effects
We should also find a way to handle that in the case of systems such as gnome-effects
C. Keyframes
We may want to handle this use-case directly in GES and for any kind of
time related configuration? FIXME
=> Special specifications for that?
@ -81,12 +86,16 @@ C. Keyframes
UC-1. The user wants to add an effect to an entire clip => GESTimelineObject new API
UC-2. The developer wants to allow his users to configure effects => New
UC-2. The developer wants to allow users to configure effects => New
GESTrackOperation API
UC-3. The user wants to add an effect on a special portion of a clip, we should
allow him to configure that thanks to a system of keyframes. FIXME
==> EDWARD : Just change the in-point/duration/start of that
effect within the TrackObject. See the mapping document and
feature within GESTimelineObject.
UC-4. We want to implement an effect which isn't only composed by a bin, but is more
complexe than that (ex: "effect '24'") => we have the GESTrackOperation
which is the base class (abstract) for this kind of implementation. This class should
@ -112,6 +121,15 @@ C. Keyframes
* property-changed: emited when a property of the GESTrackObject gst element
is changed
==> EDWARD : So this would be exactly the same signal as
GObject's 'notify' ? Or at least it's very similar to
GstObject's deep-notify feature. Might want to look into
that (not for using it, but for how it's implemented).
Same comment about the set/get properties. Maybe the
GstChildProxy interface would be worth a look also.
/**
* ges_track_object_list_gst_properties:
*
@ -164,6 +182,8 @@ C. Keyframes
* effect-removed: emited when an effect is removed
* effect-moved: emited when an effect is moved
==> EDWARD : What do you mean by 'moved' ?
/**
* ges_timeline_object_add_effect:
*
@ -245,7 +265,7 @@ C. Keyframes
=================
TODO GESRegistry API:
This should be a singleton since we don't want an app to instanciate more
than one registry. It should be able to get effects from various sources.
than one registry. It must be able to get effects from various sources.
We should also make sure any custom effect is detected.
/**