Audio Mixer and DSP

Digital Signal Processing research project

This was a term-long school assignment, running during fall of 2015. It was an opportunity to explore a wide range of concepts, many of which were completely new to me. By the end of this project I had my first experiences in:

• Low-level Win32 multimedia functions
• The C# language
• Integrating C code with C# code
• The Windows clipboard

The concepts researched included:

• The discrete Fourier tranform (DFT)
• Filtering via DFT, Convolution
• Convolution and Filtering faster
• Windowing your filters and DFT (just for viewing)
• Finite and Infinite Impulse Response Filters and filtering in real-time!
• Time and pitch shifting

Controls:

Mixer:

• Buttons to click for primary actions: New, Open, Save, Record, Stop, Play/Pause
• Menu items for changing sampling rate, bit depth, channels. (note: only 8-bit and 16-bit are fully supported)
• Menu items for special effects (reverse, amplify,

WaveForm:

• Can be resized, Time/Freq domain panels can be resized as well by dragging divider.
• Additional information about selection and wave file found in status bar at bottom.
• Select in time or freq domain with mouse -> click & drag
• Scroll mousewheel to zoom in/out in time domain
• Playback plays only current selection, or current selection to the end if a single point.
• Filter and Window by (first selecting, and then) right-clicking in the time domain. Select frequencies to curtail.
• Hotkeys:
  • <spacebar>: play
  • <shift> (home | end): expand or move the current selection marker to the start/end of the timeline (time domain)
  • <delete>: Delete selected frequencies in the frequency plot. (uses default filter: convolution)

Assets:

Code Files:

File	Description
Complex.cs	Complex numbers. Used in DFT
DSP.cs	DSP algorithms, and effects.
FourierPanel.cs	UI element, displays frequency domain. Also manages frequency selection.
Fraction.cs	For converting a double to a low-magnitude fraction. Used in resampling.
Mixer.cs	Main UI window, has menu and buttons. Initiates most functionality. Controls, playback, but only via a WaveForm
Program.cs	Main function. Starts Mixer.
WaveFile.cs	Object that contains wave header and samples. Controls reading/writing. Has cut, copy, paste functions.
WaveForm.cs	Main wave UI window. containes WavePanel and FourierPanel. Manages playback, user interaction, clipboard actions
WavePanel.cs	Draws a sample set to screen. Allows interaction: zooming, scrolling, selecting.
WavePlayer.cs	Spawns a thread to handle playback. All C#, using some win32 functions.
WaveRecorder.cs	Spawns a thread to handle recording. All C#, using some win32 functions.
WinmmHook.cs	Definitions for WaveHeader and WaveFormat structs. Imports win32 function calls

Images:

New, Open, Save, Play, Pause, Stop, Record. Disabled versions of all but pause. All in png format, created by Joe.