User`s manual

Alcorn McBride Digital Video Machine HD User’s Manual Rev 1.0
18
Playlist Control
Playlists provide a mechanism for the Digital Video Machine to automatically execute
commands in a predefined sequence. Playlists often allow the DVMHD to be used to
perform complex functions that would normally require an external controller. Since
Playlists can execute any of the commands listed in the Command Protocol section,
they can perform a variety of functions. These functions could be something as
simple as looping a single track, or as complex as user-prompted pacing of playback.
Overview
A playlist zero
(PLY00000.LST) will
automatically play on
power-up.
It is not a good idea to
have both a playlist
file and a video file
with the same number
(like PLY00002.LST
and VID00002.MPG).
If you do,
commanding the
DVMHD to play file #2
may not produce the
desired result
(whatever that may
be) since the DVMHD
is forced to prioritize
which file type it
should play in that
circumstance.
A playlist file is nothing more than a list of DVMHD commands in a text file.
These commands, which are listed in the Command Protocol section, are the same
commands that are used by all of the DVMHD’s control interfaces. Although any of
the supported commands can be used, playlists usually contain Play commands,
which cause the DVMHD to play video clips from the Compact Flash card. When a
playlist is being used, the commands are processed in the order in which they appear
in the list. The playlist is an ASCII text file and can be made using any ASCII text
editor (like notepad) or using the Playlist Builder program available from
http://www.alcorn.com/support/software.html
.
A playlist can be triggered by Serial or Ethernet commands, as well as Inputs on the
Input/Output Control connector. As a matter of fact, triggering a playlist is exactly like
triggering a video file to play. For example, let’s say you send the DVMHD the
following serial command:
2PL<CR>
This command will cause the playlist file PLY00002.LST to start playing. Using
Input/Output Control to play file #2 will also start PLY00002.LST.
It is a very common requirement in applications for the DVMHD to power up and
launch a playlist on its own. This can easily be done by naming the playlist file
PLY00000.LST. This assigns the playlist file to be clip #0, which directs the DVMHD
to play the file upon power up. Since this playlist is associated with clip #0, you can
manually start the playlist using any of the control interfaces by specifying clip #0 as
the file parameter.
It is also common practice to have one playlist launch another playlist. This is done in
the same fashion as playing a video; by using a command like 2PL (where 2 is the
number of another playlist). When another playlist is launched, execution of the
current playlist will be terminated and the new playlist will begin immediately.