Mobile DLS is based on the DLS-2 file format and supports both DLS-1 and DLS-2 technologies through the use of mechanisms introduced in the DLS-2 specification. Mobile DLS departs from previous DLS specifications in a few notable ways, including:
- The technical distinction between melodic programs and percussion programs no longer exists. There is now a single bank + program space, and any bank + program address can hold either type of program. (ulBank bit 31 no longer treated as part of bank + program address.)
- Wavetables are no longer limited to 16-bit or 8-bit linear PCM. There is an extensible mechanism allowing the use of other encodings besides linear PCM, including compression codecs. (Table of Codecs )
- It is possible to implement a Mobile DLS device without DCF and Vibrato LFO, however such an implementation will not be able to play instrument content that is authored to require those features.
- Minimum device requirements including polyphony and system sampling rate have been relaxed due to the limitations of mobile devices. Reverb and chorus have been made optional, and all voice allocation decisions are left to the implementor.
- Several corrections to the DLS 2.1 text in regard to the DCF, connection transform curve specifications, note exclusivity, and other matters, which were subsequently adopted for DLS 2 as v2.2.
The Mobile DLS Specification also contains requirements that enable compatibility with SP-MIDI format Standard MIDI Files (SMF), such as a requirement for a General MIDI 1 or 2 instrument set.
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