Tips & Tricks

Here is a collection of hints and code snippets related to NewAC or audio processing in general.

Documentation Note

If you’re inserting a single snippet, put a new topic in the Snippets section. If you’ve got a mini-tutorial, make a new section.

Summary

Tips & Tricks	Here is a collection of hints and code snippets related to NewAC or audio processing in general.
Snippets	Bits of code to do things related to NewAC.
How to decrease the delay before audio playback	The TDXAudioOut component buffers its output in order to make it smoother.
How not to crash or hang when exiting an application	If you exit a NewAC application while it is playing without stopping it, it may crash or hang.
Create Class Based on Filename	These functions create a TAuFile component of a class based on the file extension of a filename.

Snippets

Bits of code to do things related to NewAC.

Summary

How to decrease the delay before audio playback	The TDXAudioOut component buffers its output in order to make it smoother.
How not to crash or hang when exiting an application	If you exit a NewAC application while it is playing without stopping it, it may crash or hang.
Create Class Based on Filename	These functions create a TAuFile component of a class based on the file extension of a filename.

How to decrease the delay before audio playback

The TDXAudioOut component buffers its output in order to make it smoother. This buffering introduces some delay at the beginning of audio playback.

You can decrease the delay by decreasing the size of the TDXAudioOut buffer. The size of this buffer is set up by the DS_BUFFER_SIZE constant in ACS_DxAudio.pas.

If you decrease the buffer size you may also want to decrease the DS_POLLING_INTERVAL value which determines how often the component requests data from its input.

How not to crash or hang when exiting an application

If you exit a NewAC application while it is playing without stopping it, it may crash or hang. To prevent this, provide an OnClose event handler for the form where NewAC components reside. In this hander call Stop methods for all output components. A typical OnClose handler might look like this.

procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  DXAudioOut1.Stop(False);
end;

You pass Stop a False value if you are closing an application and don’t want any events. Remember that it is not harmful to call Stop even when the output component is idle.

Create Class Based on Filename

These functions create a TAuFile component of a class based on the file extension of a filename.

uses
  ACS_Classes, ACS_smpeg, ACS_WavPack, ACS_Wave, ACS_FLAC, ACS_MAC, ACS_Vorbis;
...

function CreateInputFromExt(sFilename: string): TAuFileIn;
var
  sExt: string;
begin
  sExt := ExtractFileExt(sFilename);
  if sExt = '.wav' then
    Result := TWaveIn.Create(nil)
  else if sExt = '.wv' then
    Result := TWVIn.Create(nil)
  else if sExt = '.mp3' then
    Result := TMP3In.Create(nil)
  else if sExt = '.flac' then
    Result := TFLACIn.Create(nil)
  else if sExt = '.ape' then
    Result := TMACIn.Create(nil)
  else if sExt = '.ogg' then
    Result := TVorbisIn.Create(nil)
  else
    Result := nil;
end;

function CreateOutputFromExt(sFilename: string): TAuFileOut;
var
  sExt: string;
begin
  sExt := ExtractFileExt(sFilename);
  if sExt = '.wav' then
    Result := TWaveOut.Create(nil)
  else if sExt = '.wv' then
    Result := TWVOut.Create(nil)
//TODO: Find out what is used to play MP3s
//  else if sExt = '.mp3' then
//    Result := TMP3Out.Create(nil)
  else if sExt = '.flac' then
    Result := TFLACOut.Create(nil)
  else if sExt = '.ape' then
    Result := TMACOut.Create(nil)
  else if sExt = '.ogg' then
    Result := TVorbisOut.Create(nil)
  else
    Result := nil;
end;