The DLS Level 2 synthesizer consists of the following basic elements for each voice:
- A sampled sound source with loop and release
- Two 6-segment envelope generators characterized as DAHDSR (Delay-Attack-Hold-Decay-Sustain-Release)
- Two Low Frequency Oscillator (LFO) generators
- A low pass filter with resonance and dynamic filter cutoff frequency
- Standardized response to MIDI controllers
The device must meet the following minimum requirements to be considered compliant with the DLS Level 2 specifications:
- Minimum of 32 digital oscillators each with individually controlled DCA, DCF, LFO generators (two per oscillator), and envelope generators (two per oscillator).
- Minimum sample playback rate of 22.05 KHz
- Minimum sample memory of 1,048,576 x 16-bit words
- Minimum of 512 waves stored simultaneously (subject to sample memory constraints)
- Minimum of 256 instruments stored simultaneously (subject to articulation data constraints)
- Minimum of 1,024 regions stored simultaneously (subject to articulation data constraints)
- Minimum of 8,192 explicit connections stored simultaneously (does not include default connections)
If the device claims support for both DLS and GM, it must be able to support both of them simultaneously without encroachment on the above minimum requirements.
DLS Level 2 introduces new functionality into the control logic, namely a block called a "Conditional Chunk." Conditional Chunks can be used to create libraries that are both forward and backward compatible. As an example, an instrument in a library may contain DLS Level 1 chunks, DLS Level 2 chunks, and chunks for a proprietary device. The file parser will then select the appropriate chunks for the specific device in use.
- The DLS-2.1 Amendment of January 2000 changed the MOD LFO to Gain control to bipolar, non-inverted.
- Some editions contained an error regarding Response to Reset All Controllers. Expression (CC11) should be reset.
- Some editions contained errors in the dls.h file described in the appendix. The correct dls.h and correct dls2.h are on the MMA web site.
- The DLS-2.2 Amendment corrects additional errors in the 2.0 and 2.1 documents.
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