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program Streaming;
{$mode objfpc}
uses
ctypes, nds9, maxmod9;
var
sine: cint; // sine position
lfo: cint; // LFO position
const
// waveform base frequency
sine_freq = 500;
// LFO frequency
lfo_freq = 3;
// LFO output shift amount
lfo_shift = 4;
// blue backdrop
bg_colour = 13 shl 10;
// red cpu usage
cpu_colour = 31;
function on_stream_request(aLength: mm_word; aDest: mm_addr; aFormat: mm_stream_formats): mm_word;
var
target: pcint16;
len: cint;
sample: cint;
begin
target := aDest;
//------------------------------------------------------------
// synthensize a sine wave with an LFO applied to the pitch
// the stereo data is interleaved
//------------------------------------------------------------
len := aLength;
while len <> 0 do
begin
sample := sinLerp(sine);
// output sample for left
target^ := sample;
inc(target);
// output inverted sample for right
target^ := -sample;
inc(target);
sine := sine + sine_freq + (sinLerp(lfo) shr lfo_shift);
lfo := (lfo + lfo_freq);
dec(len);
end;
result := aLength;
end;
var
sys: mm_ds_system;
mystream: mm_stream;
begin
//----------------------------------------------------------------
// print out some stuff
//----------------------------------------------------------------
consoleDemoInit();
iprintf( #10' Maxmod Streaming Example '#10);
//----------------------------------------------------------------
// initialize maxmod without any soundbank (unusual setup)
//----------------------------------------------------------------
sys.mod_count := 0;
sys.samp_count := 0;
sys.mem_bank := nil;
sys.fifo_channel := FIFO_MAXMOD;
mmInit( @sys );
//----------------------------------------------------------------
// open stream
//----------------------------------------------------------------
mystream.sampling_rate := 25000; // sampling rate = 25khz
mystream.buffer_length := 1200; // buffer length = 1200 samples
mystream.callback := @on_stream_request; // set callback function
mystream.format := MM_STREAM_16BIT_STEREO; // format = stereo 16-bit
mystream.timer := MM_TIMER0; // use hardware timer 0
mystream.manual := 1; // use manual filling
mmStreamOpen( @mystream );
//----------------------------------------------------------------
// when using 'automatic' filling, your callback will be triggered
// every time half of the wave buffer is processed.
//
// so:
// 25000 (rate)
// ----- = ~21 Hz for a full pass, and ~42hz for half pass
// 1200 (length)
//----------------------------------------------------------------
// with 'manual' filling, you must call mmStreamUpdate
// periodically (and often enough to avoid buffer underruns)
//----------------------------------------------------------------
SetYtrigger( 0 );
irqEnable( IRQ_VCOUNT );
while true do
begin
// wait until line 0
swiIntrWait( 0, IRQ_VCOUNT);
// update stream
mmStreamUpdate();
// restore backdrop (some lines were drawn with another colour to show cpu usage)
BG_PALETTE_SUB[0] := bg_colour;
// wait until next frame
swiWaitForVBlank();
// set backdrop to show cpu usage
BG_PALETTE_SUB[0] := cpu_colour;
end;
end.
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