The Swezey Digital Filter Program			June 15, 2014

Operators Instruction Manual

Installing the Program

You can place the program ("SwezeyDsp.exe") into any subdirectory. I recommend creating a top level directory for it such as "C:\SwezeyDsp" or a subdirectory for it in the "C:\Program Files" directory such as "C:\Program Files\SwezeyDsp". 

The program will remain completely contained inside that subdirectory.
It automatically creates several ".ini" files when you run the program and stores them in that directory.
Any WAV file output recordings you make using the program will also be placed in that directory.

The program uses no other files, needs no special install or uninstall.
The program does not communicate over the internet in any way to anywhere else.
You can simply delete the directory to completely remove the program and it's files from your PC.

If you want to create a shortcut to the program click on it with the right mouse button and select "Create Shortcut". 

You can cut and paste (or "drag and drop") that shortcut to the Desktop or any other directory you like. 

Puting a shortcut into the "C:\WINDOWS\Start Menu" directory will cause it to show up on your Windows "Start" menu.

You may want to create a shortcut to the directory where you store the input WAV files you want to filter. Placing it in the program's directory will have it show up in the file list when you select an input WAV file name. 

The Preconfiguration Window

To simplify configuration, this window allows you to select whether you are going to use the program for realtime filtering (shortwave listening) or to filter pre-recorded WAV files (phonograph recordings).

Simply click on one of the two large buttons in the lower center of the window.

Click on the "Continue" button to go on to the next window.

If you select "Hide" this window will be skipped at start up and will use previous settings.
You can un-Hide this window later by deselecting "Hide Preconfiguration Window during Program Start Up" under the "Help" Menu 

The I/O Configuration Window

This window is only displayed at start up time.

If you selected one of the options on the Preconfiguration Window, you shouldn't need to change anything here.

Shortwave Listening (SWL) Specific 

For live filtering (Shortwave Listening) you need to select "Use Live Input".

If your computer has trouble running the program in real time you can try reducing the Sample Rate and/or using a smaller FFT size.

Prerecorded WAV Files Specific 

Select Stereo only if you need to process stereo audio such a 33 1/3 RPM LP or 45 RPM stereo record or a stereo tape recording.

All 78 RPM records are monaural so do NOT select stereo for them.

Selecting "Pseudo-Stereo Output" ("false stereo") will spread the output audio to create a slight artifical stereophonic effect which you may find more enjoyable. This is generally only useful for music.

The Sample Rate and Bits per Sample are taken from the input WAV file you select and cannot be changed here.

The FFT size must be a power of 2 (i.e. 256, 512, 1024, 2048, 4096, 8192, etc.).
Large FFTs provide better resolution but add significant processing overhead.

Settings here are stored in an .ini file for use in future runs.

If you select "Hide" this window will be skipped at start up and will use previous settings.
You can un-Hide this window later by deselecting "Hide I/O Configuration Window during Program Start Up" under the "Help" Menu 

The Main Menu

Select the "Profile" that best describes how you will be using the program.
. 
Please pay special attention to features below that are designated - [Key Feature].
You may want to manually adjust these to get the best results. 

Please note: "Acoustical Recording" refers to ANY recording made prior to 1925.
"Electrical Recording" refers to 78 RPM phonograph recordings made after 1925. 

Please note:  FFT refers to the Fast Fourier Transform, a mathematical method 
to break up an audio signal into component frequency "bins" for detailed analysis. 
This is used extensively in this program.

The Controls Menu

Wave File Input Control

Shows or hides the program's Wave File Input Control. This control allows you to select a WAV audio file 
for input to the program. (This item is NOT shown if "Use Live Input" is selected on the Wave I/O 
Configuration Window at startup).

This control also selects prefilteres that are applied to the WAV file immediately before any other 
processing is performed. 

These are automatically set depending on the Profile selected but you can manually set them also.

The program only accepts and creates audio files in a MS-Windows PCM WAV format.

Audio files in other formats must be converted to one of these formats to be used as input into the program.

Capture Input / Output Control

Shows or hides the program's capture input or output controls. These controls allow you to capture (record) the 
audio input to or output from the program. The format of the output file is derived from the same as the input file.
The Capture Input Control is not used with WAV input files since you already have the audio in a file.

These files have a unique predefined name derived from the date and time such as:
_CaptureOut 20070405 132016 574
which was created on April 05, 2007 at 13:20:16 and 574 millesceonds.

Everytime you press the "New File" a new file is created.
If an existing file has zero length it is discarded if not it is closed.
You can rename the file after exiting the program.

Audio Input / Output Level Controls

Shows or hides the program's input/output level controls. These controls adjust the internal input level to 
the filter and the internal output level from the filter. These are not "Volume Controls". They boost or throttle 
weak or strong input/output signals and are also used to set the signal level in Capture Files. Setting them 
too high will result in severe clipping and distortion. Setting them too low can make the signal inaudible. 
Leaving them centered should work fine in most situations.

Stereo Combiner Control - [Key Feature]

This controls how the Left and Right channels are to be added together when combining stereo input into 
monaural output. 

This feature only applys if the input is in stereo and the output in monaural.

Simply Add Channels Together

Simply add the Left and Right channels together when combining stereo input into monaural output.

Use Data Common To Both Channels Only - [Key Feature]

Use only data that appears in both the Left and Right channels when combining stereo input into monaural output. For example: when a 78 RPM record is played on a modern stereo phonograph the monaural music appears the same in both channels but each channel has its own random noise. This feature allows the signal to pass through but reduces the random noise since it is not common to both channels. There are two different algorithms provided to do this the second usually works best.

Invert Right Channel and Add Channels Together

Playing  Edison Diamond Disc recordings and other so called "hill and dale" or "vertical cut" records on 
a modern stereo phonograph results in the two stereo channels being 180 degrees out of phase with each 
other. When combined to form monarual the signals cancel each other. 
This feature inverts the right channel to avoid this.

Invert Right Channel and Use Common Data Only

Combines the two previous features.

Use the Left Channel Only
Use the Right Channel Only

Use only the Left or the Right channel when combining stereo input into monaural output instead of 
adding them together. This is not commonly needed.

Spectral Subtraction Control 

This control allows you to vary the level of constant (background) noise. 
It can substantially reduce background noise but does impact the signal.
Use as little as necessary for best results.

Compression Control 

This allows you to compress the dynamic range of the signal (i.e. the difference between loud and soft 
sounds).

Expansion Control

This allows you to expand the dynamic range of the signal (i.e. the difference between loud and soft sounds). This may useful to reduce low level backgrond noise. 

Low Frequency Turn Over /  High Frequency Roll Off Controls - [Key Feature]

These are used for "electrically" recorded 78 RPM phonograph recordings ONLY (ALL 78 RPM records made after 1925).

Most of these records were recorded using one of several equalization methods depending on manufacturer and year. 

These are defaulted to use the RCA 1938 curves which work well for most records.

Proper equalization can significantly improve reproduction. 

If the Low Frequency Turn Over is set too low there is no base if too high the base is to boomy.
If the High Frequency Roll Off is set too low it will sound "tinny" if too high there is no treble.

Unfortunately curves for some companies are not known and you will have to adjust these.
Try each of the predefined curves to see what's close and then adjust as needed.
You should try to make the sound sound as natural as possible.

Bin Equalizer Control - [Advanced]

This control allows you to boost or reduce the audio for each FFT bin. 
The number of bins is half the FFT size.
To reduce over head this feature is defaulted OFF.
Select "Enable Bin Equalizer" under "Options" on the Bin Equalizer Control's menu.

Bin Auto Equalize

Select "Enable Bin Auto Equalize" to have the program auto equalize the signal.
Frequency usage in the signal is compared to frequency usage of a modern recording.
Weak frequencies are then boosted and strong frequencies are reduced to make them match.

Early acoustical recording equipment (pre-1925) generally had a very uneven frequency response.
This is intended to correct for this.

This works best with frequency rich audio such as an orchestra or band recording.
It works poorly when there are very few frequencies in play such as in a vocal or violin solo. 

This feature is adaptive and needs to run for a few seconds to adjust to the audio signal.
You should find a frequency rich portionof the recording and let the program adapt to it.

Then deselect "Enable Bin Auto Equalize" and restart the recording from the beginning.
You may want to adjust the bin levels manually to obtain the best result.

Limit Maximum Amplitudes

This keeps auto equalization from boosting an individual frequency too high.
If the boost factor exceeds 10 it is cut to 1 on the assumption it is in error.
However there are times where you may want this to adjust beyond that point.
Deselecting this allows that.

During auto equalization you can disable an individual bin and adjust it manually by deslecting the "A" button above it's slider..

Clicking on the "C" button below a slider disables it and centers that bin to be flat (neither boosted nor reduced).

Harmonic Enhancer Control - [Advanced]

This effect is slight and tricky so you may prefer not to use it.

Acoustical recordings (pre-1925) typically only recorded frequencies up to about 3400 Hertz.
This control takes the upper part of the signal, doubles it and adds it back in to create overtones above 
3400 Hertz to try to restore what is missing.

Using it with Bin Auto Equalize above I usually reduce this to 80 or 60 after I deselect Bin Auto Equalize.
If  this is set too high the sound is very tinny sounding.

High Pass and Low Pass Variable Pre-Filter Controls

These allow you to reduce the low or high frequency range of the signal and are applied at the very before the FFT is applied. 
These are usually not needed.

High Pass and Low Pass Variable Post-Filter Controls

Same as the Pre-filters except these are applied at the very end of processing. 
These are usually not needed.

Bypass Most Filtering

Causes the program to pass audio through without any filtering. 
This allows you to quickly see the effect the filter is having on the signal.

Exit the program

Exits the program.

The Profile Menu - [Key Feature]

Select a "Profile" that best describes how you will be using the program.

The Profile you select automatically sets numerous other settings for you to quickly configure the 
program for the specific type of filtering you want to do.

No Profile (no action) use this if you want to manually set all settings - this leaves current settings as is.
Reset Profile (clear ALL to OFF settings) use this to clear all settings and then drop into "No Profile".

Shortwave Listening for features specific to Shortwave Radio Listening.
Electrical Recording for 78 RPM phonograph recordings recorded since 1925.
Acoustical Recording for ANY recordings made before 1925.
High Fidelity Recording for modern sources such as from Tapes, LP and 45 RPM records.

The Display Menu

Use FFT for Display Only (NOT for Filtering)

Uses the FFT* to create the display but bypasses it for filtering. FIR and other Filters are still used. Notice 
that the background color of the display switches from black to dark gray. Features dependent on the FFT 
are also bypassed.

Show Output from FFT Instead of Input to FFT

The display can show either the input to the FFT or the output from the FFT (i.e. before/after filtering).

Show Peak/Average/Smallest Amplitudes

The display typically shows the minimum amplitude of each frequency bin in green, the difference from the minimum to the average amplitude for each bin  in blue and the difference from the average to the peak amplitude in yellow. This allows you to hide these values. This has no effect on the filtering.

Show Grid Frequencies

Shows or hides the frequency grid. This has no effect on the filtering.

Show Frequency at Cursor

Shows or hides the frequency at the cursors location. This has no effect on the filtering.

Display Frequencies 0 to nnn Hz

Selects the frequency width to be displayed. This has no effect on the filtering.

Vertical Zoom In/Out

Selects the displays vertical resolution. This has no effect on the filtering.

The Edit Menu

Normal

Sets the display to normal edit mode. Left clicking the mouse on the display window, dragging it and 
releasing it selects a range of frequencies that can be stopped or passed.

Quick Notch / Passband

Creates a narrow stopband or pass band which you can quickly moved about the display to block or pass 
a narrow band of frequencies. This filtering disappears when a different edit mode is selected.

Maximum / Minimum Amplitude

Lets you set a hoizontal line across the display depicting the maximum or minimum amplitudes allowed. 
Amplitudes above the maximum are set to the maximum. 
Amplitudes below the Minimum are set to zero.
Use the mouse or <CTRL> with the Arrow Keys to move the line up or down. 
The Minimum Amplitude can be adjusted using <CTRL> with the Arrow Keys anytime the main display window is the active window.

Reset Maximum / Minimum Amplitude

Sets the option to zero which also turns it to the "OFF" state.

The SWL Menu

These features are specific to Shortwave Listening.

Notch at 5,000 / 10,000 Hz

The most common heterodyne tones are caused by a  carrier signal of an adjacent radio station which are 
usually spaced at 5 or 10 kHz increments. These creates notches at these frequencies to remove these.

Anti-fading

This feature reduces the pumping effect produced by the Automatic Gain Control (AGC) on a Shortwave 
Receiver to produce a more even audio level.

Auto Heterodyne Reduction

This feature reduces steady tones ("heterodynes" or "whistles") from the signal automatically.

The SWL FFT Filters Menu

These features are more common to Shortwave Listening.

These are conveniently predefined FFT filters for to you to use as needed.

The Auto Options Menu

These options are automatically set when you select a Profile (recommended).

If you select "No Profile" you can set these manually otherwise these are reset to the current Profile's
default settings at program start up or whenever a new file is selected.

Undo RIAA Equalization

Older phonograph recordings were not recorded using the Recording Industry Association of America 
(RIAA) equalization curve used for most LP and 45 rpm records. This equalization curve is built into most modern phonographs. Aa result during play back old recordings are mistakenly unequalized by them. 

This feature restores a flat equalization to the play back and should be used for nearly ALL 78 RPM 
recordings. 

If you have already "undone" RIAA equalization, for example before up sampling after recording a 78 RPM at 45 RPM, you will need to turn this off when processing that file.

Auto selection of this feature can be disabled by selecting "Default Undo RIAA Equalization to OFF" under the Controls Menu.

Process FFT Frequencies from nnn to nnn

Most of the audio frequencies covered by the FFT are not actually needed. This option tells the program 
to only use the selected range of frequencies. This is solely to reduce processing overhead and speed up 
the program. If you set this manually you need to be sure it includes the entire range of frequencies you 
want to process.

Crackle Reduction Level - [Key Feature]

This is a key feature of this program. Higher levels reduce more pops, clicks and crackle but may also make the sound muddier.
This feature may mistakenly remove short tick sounds such as drums, wood blocks or castanets.
It should be reduced or turned off for such recordings.

Input/Output Smoothing - [Key Feature]

This is a key feature of this program. Old recordings frequently have a ragged sound due to pitting of the 
surface. This feature smooths the overall level to reduce this. 

Quick Set Input/Output Smoothing 

Sets both the Input and Output Smoothing levels (the feature just above) to preset values. 

The Help Menu

Hide nnnn

Hides or shows the different Welcome windows during program startup. You may want to hide all of 
them and un-hide them as needed later. 
Typically you may want to un-hide the Wave I/O Configuration Window to set different sample rates 
or FFT sizes. 
You need to restart the program to see the window.

Using the Arrow Keys to Adjust the Minimal Amplitude 

You can adjust the "Minimum Amplitude" directly by clicking on the main display (to select it),  holding 
down the <Ctrl> key and using the Arrow Keys. Raising the Minimum Amplitude can substantially reduce 
back ground noise. However setting it too high will introduce annoying artefacts.

Remember: the Demonstartion Version of the program has a periodic buzzing sound. 
There is nothing wrong with your PC.

My Web site: http://www.winternet.com/~swezeyt/dsp.htm
Your comments are always welcome, please e-mail me at: swezeyt@winternet.com

Thank you for trying the Swezey Digital Filter Program!

(c) 2014, Thomas F. Swezey. All rights reserved. (06/15/2014)