Článok o prehrávaní zvuku v Lazaruse…

Rozozvučanie reproduktorov v Lazaruse je prekvapivo netriviálne. Potrebujeme externú zvukovú knižnicu. Stránka, z ktorej som vychádzal (Audio libraries – Free Pascal wiki ) ponúka osem alternatív. Zvolil som si jednoduché filtrovacie kritérium: Ak treba na to, aby sa z reproduktorov skutočne ozval nejaký zvuk príliš veľa krokov, tak alternatívu zavrhujem. Viaceré vyzerali sľubne, ale na prvý raz sa mi podarilo prehrať zvuk len s pomocou príkladov v knižnici UOS (United OpenLib of Sound), ktorej repozitár sa nachádza na tejto adrese: https://github.​com/​fredvs/​uos/​ . Tu je obraz repozitára z 19. 3. 2020:

• uos : United OpenLib of Sound 5,26 MB (5,01 MiB), 19. 3. 2020

Niektoré príklady mi nefungovali, viaceré sú zbytočne komplikované. Jedným z najjednoduchších je SimpleDrums. Autor má dosť kostrbatý „rukopis,“ resp. „zdrojovokódopis,“ tak som sa príklad pokúsil prepísať do nového projektu:

• Simple Drums 61,44 kB (60,00 KiB), 27. 3. 2020

Výsledok je principiálne rovnaký, len je to mierne „učesané.“ Celý projekt je priamo závislý od knižnice UOS, preto musia byť obidva priečinky (uos-master aj SimpleDrums) rozbalené na rovnakom umiestnení.

Rád by som to zjednodušil, ale vyžadovalo by to ešte „trochu viac“ (skôr viac, než trochu) času. Skúste sa na to pozrieť aj v tomto stave, či to nebude náhodou postačovať. Dajte mi, prosím, vedieť. Ďakujem.

Výpis zdrojového kódu jednotky (na zviditeľnenie jej obsahu):

simpledrumsunit.pas

unit SimpleDrumsUnit;

{$mode objfpc}{$H+}

interface

uses
	Classes, SysUtils, Forms, Controls, Graphics,
	Dialogs, StdCtrls, ExtCtrls, uos_flat;

type

	{ TForm1 }

	TForm1 = class(TForm)
		Button1: TButton;
		Button2: TButton;
		Edit1: TEdit;
		Label1: TLabel;
		Timer1: TTimer;
		procedure Button1Click(Sender: TObject);
		procedure Button2Click(Sender: TObject);
		procedure FormClose(Sender: TObject; var CloseAction: TCloseAction);
		procedure FormCreate(Sender: TObject);
		procedure Timer1Timer(Sender: TObject);
	private

		sound: array[0..2] of String;
		ms: array[0..2] of Tmemorystream;
		posi: integer;
		drum_beats: array[0..2] of String;

	public

	end;

var
	Form1: TForm1;

	stopit: boolean = false;
	x: integer = 0;
	channels: cardinal = 2; // stereo output


implementation

{$R *.lfm}

{ TForm1 }

procedure TForm1.Timer1Timer(Sender: TObject);
var i: integer;
		ge: boolean = false;
begin
	Timer1.Enabled := false;
	if not stopit then
	begin
		for i := 0 to 2 do
		if (Copy(drum_beats[i], posi, 1) = 'x') then
		begin
			// uos_InputSetDSPVolume(i, 0, 0.5, 0.5, true);
			uos_PlaynofreePaused(i)
		end;

		application.processmessages; // yes or no ?

		// if uos_SetGlobalEvent(true) was executed -->
		// --> This set events (like pause/replay threads) to global.
		// One event (for example uos_replay) will have impact on all players.

		for i := 0 to 2 do
			if (not ge) and (Copy(drum_beats[i], posi, 1) = 'x') then
			begin
				uos_RePlay(i);
				ge := true; // A uos_replay() of each player will have impact on all players.
			end;

		inc(posi);
		if posi > 16 then posi := 1;
			Timer1.Enabled := true
	end
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
	Timer1.interval := strtoint(edit1.Text);
	stopit := false;
	posi := 1;
	Timer1.Enabled := true
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
	stopit := true
end;

procedure TForm1.FormClose(Sender: TObject; var CloseAction: TCloseAction);
begin
	uos_free()
end;

procedure TForm1.FormCreate(Sender: TObject);
var ordir: String;
		lib1, lib2: String;
		i: integer;
		latency : real = 0.03;
begin
	ordir := Application.Location;

	{$if defined(cpu32)}
		{$ifdef Windows}
			lib1 := ordir +
				'..\uos-master\examples\lib\Windows\32bit\LibPortaudio-32.dll';
			lib2 := ordir +
				'..\uos-master\examples\lib\Windows\32bit\LibSndFile-32.dll';
		{$endif}

		{$ifdef linux}
			lib1 := ordir +
				'../uos-master/examples/lib/Linux/32bit/LibPortaudio-32.so';
			lib2 := ordir +
				'../uos-master/examples/lib/Linux/32bit/LibSndFile-32.so';
		{$endif}

		{$ifdef freebsd}
			lib1 := ordir +
				'../uos-master/examples/lib/FreeBSD/32bit/libportaudio-32.so';
			lib2 := ordir +
				'../uos-master/examples/lib/FreeBSD/32bit/libsndfile-32.so';
		{$endif}

		{$ifdef Darwin}
			lib1 := ordir +
				'../uos-master/examples/lib/Mac/32bit/LibPortaudio-32.dylib';
			lib2 := ordir +
				'../uos-master/examples/lib/Mac/32bit/LibSndFile-32.dylib';
		{$endif}
	{$endif}

	{$if defined(cpu64)}
		{$ifdef Windows}
			lib1 := ordir +
				'..\uos-master\examples\lib\Windows\64bit\LibPortaudio-64.dll';
			lib2 := ordir +
				'..\uos-master\examples\lib\Windows\64bit\LibSndFile-64.dll';
		{$endif}

		{$ifdef linux}
			lib1 := ordir +
				'../uos-master/examples/lib/Linux/64bit/LibPortaudio-64.so';
			lib2 := ordir +
				'../uos-master/examples/lib/Linux/64bit/LibSndFile-64.so';
		{$endif}

		{$ifdef freebsd}
			lib1 := ordir +
				'../uos-master/examples/lib/FreeBSD/64bit/libportaudio-64.so';
			lib2 := ordir +
				'../uos-master/examples/lib/FreeBSD/64bit/libsndfile-64.so';
		{$endif}

		{$ifdef Darwin}
			lib1 := ordir +
				'../uos-master/examples/lib/Mac/64bit/LibPortaudio-64.dylib';
			lib2 := ordir +
				'../uos-master/examples/lib/Mac/64bit/LibSndfile-64.dylib';
		{$endif}
	{$endif}

	{$if defined(linux) and defined(cpuarm)}
		lib1 := ordir +
			'../uos-master/examples/lib/Linux/arm_raspberrypi/libportaudio-arm.so';
		lib2 := ordir +
			'../uos-master/examples/lib/Linux/arm_raspberrypi/libsndfile-arm.so';
		latency := 0.08;
	{$endif}

	uos_LoadLib(Pchar(lib1), Pchar(lib2), nil, nil, nil, nil);

	sound[0] := Application.Location + '..' + directoryseparator +
		'uos-master' + directoryseparator + 'examples' + directoryseparator +
		'sound' + directoryseparator + 'drums' + directoryseparator + 'HH.wav';
	sound[1] := Application.Location + '..' + directoryseparator +
		'uos-master' + directoryseparator + 'examples' + directoryseparator +
		'sound' + directoryseparator + 'drums' + directoryseparator + 'SD.wav';
	sound[2] := Application.Location + '..' + directoryseparator +
		'uos-master' + directoryseparator + 'examples' + directoryseparator +
		'sound' + directoryseparator + 'drums' + directoryseparator + 'BD.wav';

	// { // using memorystream
	ms[0] := TMemoryStream.Create;
	ms[0].LoadFromFile(pchar(sound[0]));
	ms[0].Position:= 0;

	ms[1] := TMemoryStream.Create;
	ms[1].LoadFromFile(pchar(sound[1]));
	ms[1].Position:= 0;

	ms[2] := TMemoryStream.Create;
	ms[2].LoadFromFile(pchar(sound[2]));
	ms[2].Position:= 0;
	// }

	drum_beats[0] := 'x0x0x0x0x0x0x0x0'; // hat
	drum_beats[1] := '0000x0000000x000'; // snare
	drum_beats[2] := 'x0000000x0x00000'; // kick

	posi := 1;

	for i := 0 to 2 do
	begin
		if uos_CreatePlayer(i) and uos_SetGlobalEvent(i, true) and
			// This set events (like pause/replay thread) to global.
			// One event (for example replay) will have impact on all players.

			// using memorystream
			(uos_AddFromMemoryStream(i, ms[i], 0, -1, 0, 256) > -1) and
			// using file
			// (uos_AddFromfile(i, pchar(sound[i]), -1, 0, 256) > -1) and
			// (uos_InputAddDSPVolume(i, 0, 1, 1) > -1) and
			(uos_AddFromEndlessMuted(i, channels, 256) > -1) then
		begin
			// this for a dummy endless input, must be last input
			if uos_AddIntoDevOut(i, -1, latency, -1, -1, 0, 256, -1) > -1 then // stereo output
			begin
				uos_PlayNoFree(i);
				sleep(250);
				// allok := true
			end // else allok := false
		end
	end;
	// if not allok then application.terminate
end;

end.