#[repr(transparent)]
pub struct TimelineElement { /* private fields */ }
Expand description

A TimelineElement will have some temporal extent in its corresponding property::TimelineElement::timeline, controlled by its property::TimelineElement::start and property::TimelineElement::duration. This determines when its content will be displayed, or its effect applied, in the timeline. Several objects may overlap within a given Timeline, in which case their property::TimelineElement::priority is used to determine their ordering in the timeline. Priority is mostly handled internally by Layer-s and Clip-s.

A timeline element can have a property::TimelineElement::parent, such as a Clip, which is responsible for controlling its timing.

Editing

Elements can be moved around in their property::TimelineElement::timeline by setting their property::TimelineElement::start and property::TimelineElement::duration using TimelineElementExt::set_start() and TimelineElementExt::set_duration(). Additionally, which parts of the underlying content are played in the timeline can be adjusted by setting the property::TimelineElement::in-point using TimelineElementExt::set_inpoint(). The library also provides TimelineElementExt::edit(), with various EditMode-s, which can adjust these properties in a convenient way, as well as introduce similar changes in neighbouring or later elements in the timeline.

However, a timeline may refuse a change in these properties if they would place the timeline in an unsupported configuration. See Timeline for its overlap rules.

Additionally, an edit may be refused if it would place one of the timing properties out of bounds (such as a negative time value for property::TimelineElement::start, or having insufficient internal content to last for the desired property::TimelineElement::duration).

Time Coordinates

There are three main sets of time coordinates to consider when using timeline elements:

  • Timeline coordinates: these are the time coordinates used in the output of the timeline in its Track-s. Each track share the same coordinates, so there is only one set of coordinates for the timeline. These extend indefinitely from 0. The times used for editing (including setting property::TimelineElement::start and property::TimelineElement::duration) use these coordinates, since these define when an element is present and for how long the element lasts for in the timeline.
  • Internal source coordinates: these are the time coordinates used internally at the element’s output. This is only really defined for TrackElement-s, where it refers to time coordinates used at the final source pad of the wrapped gst::Element-s. However, these coordinates may also be used in a Clip in reference to its children. In particular, these are the coordinates used for property::TimelineElement::in-point and property::TimelineElement::max-duration.
  • Internal sink coordinates: these are the time coordinates used internally at the element’s input. A Source has no input, so these would be undefined. Otherwise, for most TrackElement-s these will be the same set of coordinates as the internal source coordinates because the element does not change the timing internally. Only BaseEffect can support elements where these are different. See BaseEffect for more information.

You can determine the timeline time for a given internal source time in a Track in a Clip using ClipExt::timeline_time_from_internal_time(), and vice versa using ClipExt::internal_time_from_timeline_time(), for the purposes of editing and setting timings properties.

Children Properties

If a timeline element owns another gst::Object and wishes to expose some of its properties, it can do so by registering the property as one of the timeline element’s children properties using ges_timeline_element_add_child_property(). The registered property of the child can then be read and set using the TimelineElementExt::child_property() and TimelineElementExt::set_child_property() methods, respectively. Some sub-classed objects will be created with pre-registered children properties; for example, to expose part of an underlying gst::Element that is used internally. The registered properties can be listed with ges_timeline_element_list_children_properties().

This is an Abstract Base Class, you cannot instantiate it.

Implements

TimelineElementExt, glib::ObjectExt, ExtractableExt, MetaContainerExt, [TimelineElementExtManual][trait@crate::prelude::TimelineElementExtManual]

Implementations

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