<html><head><title>SqueekySynth 1.1 Instruction Manual</title></head>
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<h2>The Main Page</h2>

The main page of SqueekySynth -- that is, the page that is shown when you first start SqueekySynth, or when you click the "Main" tab -- is illustrated in the following image:<p>

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There are several important controls here, which you may need to adjust during playback for optimal results. All changes take effect in real-time and are memorized when you close SqueekySynth.<p>

The controls are described from the top down, as follows:<p>

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<dt><b>Output Meter (Output Level Section)</b></dt>
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The output meter indicates the current <i>peak</i> audio level that SqueekySynth is generating. The meter is calibrated accurately in dB, with each segment representing 1dB. Generally speaking, it is desirable to avoid the signal reaching 0dB or above. If you let this happen, the meters will "go into the red", and you may hear audible "clipping" (distortion). If this happens, use the output level slider (see below) to adjust the output level.
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<dt><b>Output Level Slider (Output Level Section)</b></dt>
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The slider immediately below the meter controls SqueekySynth's output level. It is calibrated accurately in dB, with each notch representing 1dB. Since SqueekySynth is a synthesizer, not a digital audio recorder, its output level will vary dramatically depending on how many notes are playing, and how loudly. For this reason, the default setting is -12dB, not 0dB. Generally you should keep it substantially below 0dB if you wish to avoid clipping.
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<dt><b>Clear Peak Button (Output Level Section)</b></dt>
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The "peak hold" feature of the meter serves to memorize the highest level it has encountered as a pair of dots. This enables you to see at a glance if SqueekySynth has clipped, without having to keep your eyes on the meter at all times. If you wish to clear the memorized peak (for instance, after changing the output level), click the "Clear Peak" button. Since both the meters and the output level slider are calibrated, it is possible to accurately address a clipping problem. For instance, if the peak hold indicates that +6dB was reached, the output level slider should be reduced by 6dB to ensure clipping-free audio.
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<dt><b>Sound Quality Pop-up Menu</b></dt>
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This allows you to select which resampling algorithm SqueekySynth should use. Higher settings provide better audio quality, at the expense of higher CPU usage. The default setting of "Medium" (fourth-order resampling) provides a reasonable trade-off, although you may wish to raise this to "High" (seventh-order) for critical work. "Low" (linear resampling) should only be used when CPU usage is critical, as it causes a very large loss of quality.
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<dt><b>Polyphony Slider</b></dt>
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Allows you to determine how many voices SqueekySynth can play at once. If this is set too low, notes will be audibly "cut off" in order to make room for new notes. If this is set too high, it is possible to overload your CPU by playing too many notes, resulting in audio glitches (crackle / stutter) and a very unresponsive operating system. The default setting is 128 voices, but there is no universal "optimal" setting, as it varies from computer to computer. Ideally this should be set high enough that no notes are being cut off, but low enough that the CPU is never overloaded.
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<dt><b>Panic Button</b></dt>
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The Panic button turns all notes off, resets all controllers, and selects preset #0, bank #0, for each channel. Essentially this is equivalent to a "system reset". If you are experiencing stuck notes, or a MIDI file is not playing back correctly, try pressing this button and then attempt playback again.
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<h3>Further Information About Audio Levels (Advanced)</h3>

SqueekySynth uses floating-point audio, both internally and externally. Floating point audio is a way of transporting audio that is very similar to analogue audio cables.<p>

With analogue audio cables, there is a universally defined "nominal" signal level, which is around 1 volt peak, and most professional equipment generates and expects signals in this range. However, there is no realistic limitation to the specific signal levels which can be transported over analogue audio cables. 0.1 volt peak, or 100 volts peak would also transport the audio perfectly well. With these extremes, you may need to adjust the gain on your input equipment (e.g., mixer, tape recorder, amplifier) an excessive amount.<p>

Floating point audio is much the same. Signals are represented by numbers instead of voltages, with the "nominal" level being "1". However, no quality loss is incurred by using smaller or larger signals than normal -- the only downside is, like analogue audio, the gain may need to be adjusted excessively at the receiving end.<p>

Sooner or later, digital floating point audio has to be converted to conventional 16 or 24 bit audio, in order that it can be recorded to a CD, or played through the soundcard.<p>

It is at this point where "clipping" occurs. The Media Kit Mixer, when the "Master Volume" and "SqueekySynth L/R" faders are in their default positions (0dB), treat a floating point level of "1" as "full scale", and any higher signal level (as a result of setting the gain too high in SqueekySynth, or running two different software synthesizers at the same time) will clip the outputs on the soundcard.<p>

The meters on SqueekySynth indicate 0dB when a floating point level of "1" is reached. While it is perfectly valid to set the gain higher, so the meters are running in the red, you will need to reduce the gain on the Media Kit Mixer to avoid the soundcard clipping. Likewise, if you are running close to 0dB on SqueekySynth, but have another software synthesizer playing at the same time, you will need to reduce the "Master Level" on the Media Kit Mixer, or the output levels of the software synthesizers, to avoid the outputs clipping from the sum of both signals.<p>

Unfortunately, the Media Kit Mixer, at least in BeOS R5, does not have properly calibrated faders -- it is impossible to tell where the 0dB point is, and there is no output metering. For this reason, it is suggested that you avoid touching the faders in the mixer, because it would be difficult to restore them to their 0dB point. Likewise, it is best to avoid running several audio-generating applications at the same time, as there is no output metering in the mixer. If you wish to run several applications at the same time, the best current solution is to use a BeOS-supported multi-channel soundcard (e.g. Echo Darla, Gina, Layla, Gina 24, Layla 24, Gina 3G or Layla 3G) or several different soundcards, with each audio-generating application assigned to its own dedicated pair of outputs. Under these conditions, there are no other signal sources being introduced to clip the outputs, so the built-in metering in SqueekySynth and other software synthesizers will work perfectly, even with multiple applications running at once.<p>

Hopefully the Haiku and Zeta Media Kit Mixers will address this issue in the future, and provide full output metering and detailed calibration marks for each fader.<p>

In summary, the output metering on SqueekySynth is accurate providing you have not changed the faders in the Media Kit Mixer, and providing no other audio-generating applications are producing audio at the same time.




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