Layers

A movie can have any number of layers and the storage overhead in the resulting file is negligible for extra layers. Each layer provides a canvas on which can be put any number of objects. As the layer appears, disappears or moves so will all the objects on that layer.

Layers can be of the following types

Visual layers

A visual layer can contain any combination of graphics, images and text and is covered more fully in a separate section.

Sound layers

Sound layers are not visible layers. When a sound is enabled with a 'show' event then the sound begins to play in the phone. Clicking twice on the name of a sound layer allows the current layers sound file to be replaced. Midi is the sound format of choice for mobile devices because of it's compact file size and also because of the high compression of data that can be achieved when it is included in a JAR file (anywhere between 50% and 90% compression). Other sampled sound formats such as WAV require large file sizes for relatively short duration sound.

Where the imported sound file is a MIDI file, the product automatically checks if the file is type 0 (which is the type most phones will play). If it is not then the product will offer the option to convert to type 0. Conversion is done and also all percussion sounds on midi channel 10 are removed since these are usually not heard in a phone. In addition all extraneous midi file information eg. comments, lyrics, system specific events, bank changes are removed to reduce file size further. If a specific midi type 0 file is required to be played then it is best to do the conversion with another tool before importing into the product.

Softbutton action layers

Softbutton action layers are not visible. They define an action for a softbutton on a phone. When the soft button is enabled is determined by a 'show' event on the timeline and disabling is controlled by a 'hide' event. Softbuttons are reproduced in browser applets by using standard java buttons under the applet.

The actions that can be associated with a softbutton are:

Hotspot layers

When a hotspot layer is enabled AND visible on a phone, then pressing the 'Select' button (or return key) on the device will initiate the action associated with the layer. Only one hotspot layer may be visible at any one time. Where several hotspot layers have been enabled with a 'enable' event, then it is possible to tab through the layers using the arrow keys on the phone keypad (or keyboard for an applet.

Once a particular event has been selected from a number of hotspots, all the hotspots are then disabled but they may be re-enabled later in the movie.

The actions associated with a hotbutton layer are the same as for the softbutton layer above.

Efficiency

A layer adds almost no overhead to a movie file however the player will always try to render a layer unless it's not visible. To increase player speed it is best to make a layer invisible if it is not performing any function eg. it's objects have moved offscreen. Sometimes it is better to break a large movie up into a number of smaller movies and chain them together in order to reduce the total number of layers that have to be processed.