* Basic Producers - these are typically file or device oriented feeds;
* Playlists - these are arrangements of multiple producers;
- * Tractors - these are multitrack fx encapsulators.
+ * Multitracks - these are the fx encapsulators.
- Although westley was defined as a serialisation mechanism for running MLT
- components, this document will concentrate on the hand authoring of westley
- documents.
+ In the mlt model, producers are created and attached to 'consumers' -
+ consumers are software playback components (such as SDL), or wrappers for
+ hardware drivers (such as bluefish) or even the westley serialising
+ consumer itself (the latter doesn't receive frames - it merely
+ interrogates the connected producer for its configuration).
+
+ Although westley was defined as a serialisation mechanism for instantiated
+ MLT components, this document will concentrate on the hand authoring of
+ westley documents.
Rules:
1) create producer elements for each unique media clip in the project;
2) create playlists for each track;
- 3) create a tractor for track specific filters and transitions;
- 4) create another tractor for filters that are common to the output.
+ 3) create a multitrack and specify filters and transitions;
+ 4) adding global filters.
While other uses of westley exist, the approach taken here is to maximise
efficiency for complex projects.
Notes:
- 1) All in/out points are absolute frame positions - we support PAL and
- NTSC at a system level, but westley documents are currently authored
- for a specific normalisation;
- 2) The last 'producer' in the document is the default for play out;
- 3) Playlists can reference the same producer multiple times. In/out regions
+ 1) All in/out points are absolute frame positions relative to the producer
+ being appended to the playlist;
+ 2) Westley documents are currently authored for a specific normalisation;
+ 3) The last 'producer' in the document is the default for play out;
+ 4) Playlists can reference the same producer multiple times. In/out regions
do not need to be contiguous - duplication and skipping is acceptable.
-Interlude - Introducing Tractors:
+Interlude - Introducing Multitracks:
- So far, we've defined basic producers and playlists/tracks - the tractor is
+
+ So far we've defined basic producers and playlists/tracks - the tractor is
the element that allows us to arrange our tracks and specify filters and
transitions. Similarly to a playlist, a tractor is a container.
playback speed, position, or even which producer is connected to which
consumer.
- In a later phase of MLT development, the application will be able to
- manipulate the tractors make up, by adding and removing tracks, filters
- and transitions. The consumer itself remains connected to the same object
- (the tractor).
-
The consumer receives the first non-blank frame (see below). It has no say
in the order in which gets them (the sdl consumer when used with inigo might
appear to be an exception - it isn't - it simply has a route back to the