From: "Robert Rossmair" <Robert.Rossmair@t-online.de>
Subject: Re: How to programmatically control the volume slider?
Date: Wednesday, February 07, 2001 9:03 AM

Rob schrieb:

> I want to have, on my app that uses a tmediaplayer, a slider that when
> moved, controls the sound cards output level. This is what you can do in the
> commercial media players, where they have the level slider which controls
> the output. This basically controls the volume slider of the app on the
> taskbar. Can anyone give a method or example of how to do this?

Below an example project which shows how to do this using my Mixer
component (freeware w/ source, available from
http://home.t-online.de/home/Robert.Rossmair/#TrrMixer).
To control the recording volume, replace "Playback" by "Recording".

-------------------8<-------------------8<-------------------8<-------------------
unit VolDemo1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms,
ComCtrls,
  rrMixer;

type
  TForm1 = class(TForm)
    Mixer: TrrMixer;
    VolumeL: TTrackBar;
    VolumeR: TTrackBar;
    procedure VolumeLChange(Sender: TObject);
    procedure VolumeRChange(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    procedure PlaybackVolumeChange(Sender: TrrMixer; Control:
TAudioLineControl);
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.VolumeLChange(Sender: TObject);
begin
  Mixer.Playback.Volume.Position[0] := VolumeL.Max - VolumeL.Position;
end;

procedure TForm1.VolumeRChange(Sender: TObject);
begin
  Mixer.Playback.Volume.Position[1] := VolumeR.Max - VolumeR.Position;
end;

procedure TForm1.PlaybackVolumeChange(Sender: TrrMixer; Control:
TAudioLineControl);
begin
  VolumeL.Position := VolumeL.Max - Mixer.Playback.Volume.Position[0];
  VolumeR.Position := VolumeR.Max - Mixer.Playback.Volume.Position[1];
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Mixer.DeviceID := 0;

  VolumeL.Min := Mixer.Playback.Volume.Minimum;
  VolumeL.Max := Mixer.Playback.Volume.Maximum;
  VolumeL.Position := VolumeL.Max - Mixer.Playback.Volume.Position[0];

  VolumeR.Min := Mixer.Playback.Volume.Minimum;
  VolumeR.Max := Mixer.Playback.Volume.Maximum;
  VolumeR.Position := VolumeR.Max - Mixer.Playback.Volume.Position[1];

  Mixer.Playback.Volume.OnChange := PlaybackVolumeChange;
end;

end.
-------------------8<-------------------8<-------------------8<-------------------
object Form1: TForm1
  Left = 192
  Top = 120
  Width = 217
  Height = 277
  Caption = 'Form1'
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'MS Sans Serif'
  Font.Style = []
  OldCreateOrder = False
  OnCreate = FormCreate
  PixelsPerInch = 96
  TextHeight = 13
  object VolumeL: TTrackBar
    Left = 24
    Top = 16
    Width = 45
    Height = 205
    Orientation = trVertical
    Frequency = 1
    Position = 0
    SelEnd = 0
    SelStart = 0
    TabOrder = 0
    TickMarks = tmBoth
    TickStyle = tsManual
    OnChange = VolumeLChange
  end
  object VolumeR: TTrackBar
    Left = 100
    Top = 16
    Width = 45
    Height = 205
    Orientation = trVertical
    Frequency = 1
    Position = 0
    SelEnd = 0
    SelStart = 0
    TabOrder = 1
    TickMarks = tmBoth
    TickStyle = tsManual
    OnChange = VolumeRChange
  end
  object Mixer: TrrMixer
    DeviceID = 0
    Left = 164
    Top = 16
  end
end
-------------------8<-------------------8<-------------------8<-------------------

Greetings, Robert
--
Robert Roßmair