README

Real-time Voice Changing

Real-time voice changing demo written in Delphi for .NET around 2007. It records audio from the microphone, processes it in short windows using FFT (Fast Fourier Transform) with a Hanning window, applies simple spectral transformations, and plays the processed audio back in near real time. The application also provides basic visualization of the waveform / spectral data.

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Overview

• Platform: Delphi for .NET (Borland VCL assemblies)
• Audio processing:
  • Uses a fixed window length of LenWindow = 1024 samples.
  • Each window is first passed through a Hanning window.
  • An FFT is applied to analyze the signal in the frequency domain.
  • Additional FFT passes on the real and imaginary parts are used to shape or redistribute spectral content.
  • The processed data is transformed back to a time-domain buffer and sent to the audio output.
• Real-time loop:
  • A custom TRecorder captures audio into an input buffer.
  • A custom TPlayer plays from an output buffer.
  • A timer periodically checks the recorder position; when a full window is ready, it calls Change(t) to process that block and fill the playback buffer.

This project serves as an experimental FFT-based real-time voice changing application, distinct from the matrix-precomputed Fourier-style approach used in the older “Real-time Voice Conversion” project.

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Project Structure

• VoiceChanging.dpr – Project entry point; references:
  • Main.pas – Main form, audio loop, and high-level signal processing.
  • ..\Units\Fourier.pas – FFT, Hanning window, and related math routines (external).
  • ..\Units\MultiMedia.pas – TRecorder, TPlayer, and audio I/O helpers (external).
  • ..\Units\Drawing.pas – Drawing helper routines (external).
  • ..\Component\DrawLinePoint.pas – UI frame for drawing / frequency mapping (external).
• Main.pas – Implements:
  • Setup of the FFT environment (FFTInitial(LenWindow)).
  • Buffers for time- and frequency-domain data (X, Y, A, Data, etc.).
  • The processing routine Change(t) that:
    • Copies a window from the input buffer.
    • Applies HanningWindow.
    • Runs FFT and additional transformations.
    • Writes the resulting samples into BufferPlay.
  • Visualization code (ShowShapeWave) for drawing simple waveform/analysis views.
• Main.nfm – Form definition (layout, images, panels, etc.).

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Building and Running

1. Open VoiceChanging.dpr in Delphi for .NET (e.g. Borland Developer Studio era with support for the Borland.Vcl assemblies).
2. Make sure the external units referenced in the project file exist and are in the expected relative paths:
   • ..\Units\Fourier.pas
   • ..\Units\MultiMedia.pas
   • ..\Units\Drawing.pas
   • ..\Component\DrawLinePoint.pas
3. Build the project.
4. Run the executable:
   • Ensure your microphone and audio output device are correctly configured in Windows.
   • Use the UI (e.g. clicking on the main image/button) to start and stop recording / playback.

Because the project targets an older .NET 1.1 / Borland VCL toolchain, you may need a compatible development environment or a legacy virtual machine to build and run it.

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Features

• Real-time voice changing using FFT-based processing.
• Windowed processing with a Hanning window to reduce artifacts at block boundaries.
• Custom Recorder/Player classes for audio capture and playback.
• Simple visualization of waveform / analysis data on the form.
• Experimental spectral manipulation via additional FFT passes on real and imaginary components.

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License

This codebase is shared without a formal license. It is intended for educational and personal use; you may use, study, and modify it as you wish. If you reuse or publish derivatives of this project, attributing the original Delphi/.NET “Voice Changing” demo is appreciated.