Audio Player with Reverb by Erick Tejkowsi
05-09-02

The REALbasic 4.5 development cycle is really starting to heat up! Among various improvements, REALbasic 4.5a9 adds significant new QuickTime functionality to the mix. This week we'll take a look at some of these new REALbasic 4.5 QuickTime features, focusing primarily on sound. We'll build a simple audio player, add real time reverb effects, and give users the option of saving the result. Try to do that with iTunes!

Introduction

Before you get started, you will need to download a copy of REALbasic 4.5a9 or higher. Keep in mind that REALbasic alpha releases are works in progress. You shouldn't rely on them for professional development. The features and appearance of pre release versions can change at any time. Always back up your projects when using REALbasic alpha releases. Since we will be working with existing media files this time (e.g. mp3, aif, wav, mov, etc...), it would be a good idea to make back up copies of these files as well. You don't want an errant REALbasic to wreak havoc on your only copy of that Kajagoogoo tune you snagged from LimeWire. In other words, take the usual ResEdit precautions: always keep a back up!

Build the Interface

Launch REALbasic and open Window1. To this window, add the following controls:

Arrange the interface however you wish. It might look something like this:

Source Code

Before we get started with the code, we need to do a few preliminary tasks. First, select the Edit-File Types menu. In the File Types dialog, add these two file types:

Next, double click Window1 to open the Code Editor. Select the Edit-New Property menu to create the following 3 properties:

1. e as editableMovie
2. reverb as QT3DAudio
3. sndTrack as QTSoundTrack

Okay, now we're ready for some code. Add the following code to the Action event of OpenButton:

  dim i as integer
  dim f as folderItem 
  dim trackCount,sndTrackIndex as integer
  dim foundOne as boolean 
  
  
  f=GetOpenFolderItem("any")
  if f<>nil then
    e = f.openEditableMovie
    e.SaveOnClose=FALSE 
    
    //load the player
    //with this movie
    MoviePlayer1.movie = e
    
    //find a soundtrack
    //trackCount = e.TrackCount
    trackCount = e.TrackCount
    foundOne = FALSE
    
    if trackCount>0 then
      for i=1 to trackCount
        if e.track(i).MediaType="soun" then
          foundOne=TRUE
          sndTrackIndex=i 
          //force ourselves out of the loop next time
          i=trackCount
        end if
      next
    end if
    
    if foundOne then
      sndTrack=e.SoundTrack(sndTrackIndex)
      reverb = nil
      reverb = sndTrack.Get3D
      if reverb=nil then
        //no 3D settings in this track
        //so we'll add them
        reverb = new QT3DAudio
      end if
      reverb.SourceMode=1
      reverb.RoomSize = val(RoomSizePopup.text)
      
      //attach the 3D info to the soundTrack
      sndTrack.set3D reverb
      //set the sndTrack's volume
      sndTrack.volume = val(VolumePopup.text)
      
    else
      MsgBox "No SoundTrack in this file"
      return
    end if
    
  end if
  

Next, navigate to the Action event of the SaveButton and add this code:

  
  dim exportMovie as editableMovie
  dim destTrack as QTSoundTrack
  dim f as folderItem 
  
  f=GetSaveFolderItem("video/quicktime","WithReverb.mov")
  if f<>nil then
    //create a new movie to hold the reverb track
    exportMovie=f.CreateMovie
    
    //add a new soundtrack to the movie
    destTrack = exportMovie.NewSoundTrack
    
    //copy the soundtrack from the source soundTrack
    //to the new soundTrack
    destTrack.InsertSoundTrackSegment sndTrack,0,sndTrack.duration,0,TRUE,TRUE
    
    //add a QT3DAudio object to the SoundTrack
    destTrack.set3D reverb 
    
  end if
  

The final step is to add some functionality to the two PopupMenu controls. To the Change event of RoomSizePopup, add the following code snippet:

  reverb.roomsize=val(me.text)
  sndTrack.set3D reverb

Then, add this snippet to the Change event of VolumePopup:

  if sndTrack<>nil then
    sndTrack.volume = val(me.text)
  end

Conclusion

That's it! To test, select Debug-Run. Press "Open" to load your favorite audio file. Since we left it open-ended (i.e. file type="any"), you can load many common audio formats (mp3, aif, wav, mov). Once the audio is loaded, adjust the room size (in meters) to your liking and press "Save" to save the result as a movie. You can download the finished project here. Have fun and see you next week!