VLSI
Solution
y
VS1103b
VS1103B
6. FUNCTIONAL DESCRIPTION
6.2.2 Supported MIDI Formats
General MIDI and SP-MIDI format 0 files are played. Format 1 and 2 files must be converted to format
0 by the user. The maximum simultaneous polyphony is 40 (peak polyphony 64). Actual polyphony
depends on the internal clock rate (which is user-selectable), the instruments used, and the possible
postprocessing effects enabled, such as bass and treble enhancers. The polyphony restriction algorithm
makes use of the SP-MIDI MIP table, if present. MIDI implements click-avoiding smooth note removal.
When run in Real Time RT-Midi mode without other signal paths, 36.86 MHz (3.0× input clock)
achieves 16-26 simultaneous sustained notes. The instantaneous amount of notes can be larger. 36 MHz
is a fair compromise between power consumption and quality, but higher clocks can be used to increase
polyphony. They are also needed if multiple signal paths are used.
Reverb effect can be controlled by the user. In addition to reverb automatic and reverb off modes, 14
different decay times can be selected. These roughly correspond to different room sizes. Also, each
midi song decides how much effect each instrument gets. Because the reverb effect uses about 4 MHz of
processing power the automatic control enables reverb only when the internal clock is at least 3.0×.
When EarSpeaker spatial processing is active, MIDI reverb is not used.
VS1103b supports unique instruments in the whole GM1 instrument set and one bank of GM2 percus-
sions.
Version 1.01, 2007-09-03
24
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