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-- Programmed by Jedidiah Barber
-- Released into the public domain
-- This program opens the default libao driver and plays a 440 Hz tone for one second
with
Ada.Command_Line,
Ada.Numerics.Elementary_Functions,
Ada.Text_IO,
Libao;
procedure AAO_Example is
package ACom renames Ada.Command_Line;
package Math renames Ada.Numerics.Elementary_Functions;
package TIO renames Ada.Text_IO;
My_Device : Libao.Device;
My_Format : Libao.Sample_Format;
Default_Driver : Libao.Driver_ID_Number;
begin
-- Initialize
TIO.Put_Line ("libao example program");
Libao.Startup;
-- Setup for default driver
Default_Driver := Libao.Default_Driver_ID;
My_Format := Libao.Create
(Bits => 16,
Rate => 44100,
Channels => 2,
Byte_Format => Libao.Little_Endian,
Channel_Matrix => Libao.Stereo);
-- Open driver
begin
My_Device := Libao.Open_Live
(Driver_ID => Default_Driver,
Format => My_Format,
Options => Libao.Empty_Options);
exception
when Libao.Open_Device_Error | Libao.General_Failure =>
TIO.Put_Line ("Error opening device.");
ACom.Set_Exit_Status (ACom.Failure);
return;
end;
-- Play some stuff
-- This sine wave generation was directly translated from the C example,
-- but it ends up being a little messy playing fast and loose like this.
declare
Buffer : Libao.Data_Buffer (1 .. 16 / 8 * 2 * 44100);
type Wraparound is mod 65536;
Sample : Wraparound;
begin
for I in Integer range 0 .. 44100 - 1 loop
Sample := Wraparound (Integer (0.75 * 32768.0 *
Math.Sin (2.0 * Ada.Numerics.Pi * 440.0 * Float (I) / 44100.0)) mod 65536);
-- Put the same stuff in left and right channel
Buffer (4 * I + 1) := Character'Val (Sample and 16#FF#);
Buffer (4 * I + 2) := Character'Val ((Sample / 256) and 16#FF#);
Buffer (4 * I + 3) := Character'Val (Sample and 16#FF#);
Buffer (4 * I + 4) := Character'Val ((Sample / 256) and 16#FF#);
end loop;
Libao.Play (My_Device, Buffer);
end;
-- Close and shutdown
-- Technically the binding will take care of closing open devices at shutdown,
-- but it is always good practice to close them anyway.
Libao.Close (My_Device);
Libao.Shutdown;
end AAO_Example;
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