Omnia 3 Processing Setup

Overview

Standard audio processing for Z/IPStream R/2 is the Omnia 3-band processor. Omnia 3 is intuitive and easy to use. Applying audio will activate movement on the bar graphs, and this is confirmation that processing is occurring.

All audio processing adjustments are performed in the Preset Editor. A “preset” is simply a large table of values representing all of the control values for every control listed in the menu tree. When you choose a preset, the control values are loaded into the processing structure, reconfiguring Omnia 3.

We recommend exploring the provided factory presets. Then, once you find the preset that most closely matches the sound you’re after, you can customize it to your liking. More information about Omnia 3 preset management can be found in Chapter 13 of this manual.

Understanding the Omnia 3 Bar Graphs and Indicators

The bar graphs are capable of indicating more than just level information. The texture and density of the audio signal can be observed, based upon the dynamic action of the bar graphs, and peak-responding “pills”. Of interest are the “pills” at the end of the input and output meters, as they indicate peak level. The bar  represents the RMS average of the signal. Wide dynamic range will display a separation between the pills and the bar, whereas signal with little peak information will cause the pills to ride on the crest of the bar graph. The bar graphs can indicate up to 25 dB of gain reduction.

The bar graphs provide a wealth of information about the processing control in Omnia 3. The algorithms automatically adapt the style of compression/limiting control being employed on a moment-by-moment basis. This can be deduced if the metering is studied over time. During normal operation, the indicators will have a dynamic “bounce” that you will be able to get a feel for. Every now and then, you will see the processor react quickly and show a larger amount of gain reduction. Notice that the response is very fast. This action will recover very slowly, and return to “rest” with the main bar graph. This action will be easily noticed on material that is very dynamic in texture. More on this below.

Another feature unique to Omnia 3 is processor “Hold”. During brief pauses in audio, the bar graphs will “freeze” and the GATE indicators will show the processor has entered the Hold mode of the algorithm. This is most easily noticed when there is a “dry” voice being processed.

The Input/Output level meters will change from green to red whenever the level exceeds –12dBfs. The pills also change color on the Input/Output displays. In the dynamic processing , the pills maintain the same color.

Note: The input and output levels are displayed relative to 0dB full scale (0dBfs). The 0 indicator on the input/output bar graphs means that every available bit of signal level is being used at that time! There is nothing more in the level department, except to create distortion… nasty sounding distortion!

Interpreting the Gain Reduction Meter Displays

Through careful observation of the processing bar graphs, significant information can be acquired and analyzed about the audio signal on a moment-by-moment basis. The bar shows the average value of the gain reduction, while the floating pill indicates the peak value of gain reduction.

Since the processing algorithms in Omnia 3 ‘adapt’ to the audio, it is capable of performing many different processing functions at different times. The processing display bar graphs may appear to indicate different kinds of operation with different program material. This behavior is primarily based on dynamic range differences in the applied program material. For program material that is already processed or lacking dynamic range, the bar graphs will indicate differently than with material that possesses a high degree of dynamic range. This is because audio signals that lack dynamic range, naturally or by previous processing, will possess a lower peak to average ratio. Conversely, audio signals with a wide dynamic range possess a higher peak to average ratio. The Omnia 3 adapts differently to each case.

For program material that has low dynamic range (or high RMS and low peak levels), there will be more activity in the WB-AGC s and less activity in the Multiband Processors. This behavior is due to the WB-AGC response to high RMS energy, while the Multiband  is reacting to lower peak energy. Sometimes the Multiband  may not indicate any action at all. For Omnia 3, this is completely normal! Examples of this behavior might be seen with heavily processed commercials or music, or with music passages of sustained level. A good example is the Aerosmith album “Pump.” This recording has very little dynamic range. Try any up-tempo selection from this recording and you will see the Wideband-AGC  make initial adjustments along with small amounts of limiting. Once adjusted, the Wideband-AGC  will stay deep in gain reduction, although with little movement, and action within the limiters will be minimal.

When the programming has wide dynamic range (low RMS and high peak levels), the opposite will occur. The Multiband  becomes active, while the WB-AGC  will appear not to respond as much. During these events, the Multiband s could be working aggressively, while the WB-AGC  indicates little activity. Good examples of programming able to cause this behavior: vocal passages, live voice, classical music, and passages with high transient levels. Good test examples: almost anything classical, as well as almost anything by Steely Dan!

Also keep in mind that the WB-AGC  is designed to operate much more slowly than the Multiband s, primarily because of the nature of each function. Remember that the WB-AGC  operates on the program’s RMS energy. During gain calculations, the incoming program’s “average” level is established, and gain adjustments, if needed, are made based on those calculations. This is why the WB-AGC s will appear to move slower as it makes changes over relatively long time periods.

The intent of the Multiband  is to normalize the spectral balance and provide control of the peak levels. Peak energy must be detected and adjusted in a quick and accurate manner while, at the same time, not interfering with the sonic integrity of the audio signal. For this reason, the Multiband s operate faster, with special background instructions to govern their behavior, and strictly on an as-needed basis.

Since the processing displays are capable of providing a wide range of information, we do not recommend setting up the system based on any specified meter indications. Instead, we recommend setting up the processing by using your ears to judge the sound. We’ve provided the meters only to analyze the signals and aid you in adjusting the specific parameters needed to achieve your desired sonic results. Like a speedometer, the meters are a guide, not the road!

The red ticks that appear above the WB (Wideband AGC), L (Low-Band AGC), M (Mid- Band AGC), and H (High-Band AGC) bar graphs are the GATE indicators. They display GATE activity. The GATE function is described above in the  titled “Understanding the Bar graphs and Indicators”

Editing Presets

Once a at least processing or processing/encoding instance has been defined, you are ready to begin the editing process. From the main “Control Panel” screen, click on the pencil icon to the right of the preset name in the desired instance, and you will be presented with a block diagram of the Omnia 3's audio path. Clicking on any of the blocks takes you to the controls available for that . Once you've made your adjustments, click Save or Cancel, depending on whether or not you like what you hear.

Input

Clicking on the Input block displays the input  sub-menu. There are adjustments for the individual Left/Right channels. Drag the slider-bar to adjust the respective level. There is a 30dB range of adjustment between –20dB and +10dB.

Using normal program audio, a correct gain setting results in peak indications (the“bouncing balls”) hitting -12 dBFS (where the level meters turn red) or a little higher. This corresponds to system headroom of 12 dB. You may adjust for more headroom if you wish (lower indications), but setting the input level for less headroom (higher meter indications) is strongly frowned upon.

Wide Band AGC

A very flexible wideband leveler  provides smooth, transparent control of the input program. This is achieved through two significant Omnia innovations: a dual referenced release gate and a hidden, intelligent “makeup” gain algorithm. The dual gate reference is a unique process that correlates the dynamics of the audio input signal to a “rolling” reference level, and from that information makes conditional decisions affecting the character of the release function.

A hidden, Make-Up Gain, control signal determines when the amplitude of the input program suddenly falls to a reduced level. It then adjusts the side chain gain in order to “fill in” the softer program passages so that the average level is increased. This allows the AGC function to operate with slower time constants, while significantly increasing the average audio level. These slower overall time constants yield lower intermodulation distortion, contributing to Omnia’s trademark sound.

Using Classical music for an example, the orchestra often plays forte, and then enters abruptly into a quiet passage. Conventional AGC algorithms would hold the softer passage down until it was able to slowly recover at the static release time setting, making such passages nearly inaudible at normal listening levels. Omnia 3’s makeup gain function allows a hidden, faster time constant to provide quick recovery, but only during the softer passage. As soon as the orchestra starts to play louder, the “makeup” time constant yields control back to the primary AGC circuit, returning gain to the previous platform level. This sophistication preserves the dynamic integrity of the signal while greatly enhancing the listenability of the program.

This is the first processing  within the Omnia 3, so the controls in this  affect the overall signal, its density, and hence affect every other processing  following it. The job of the Wideband AGC is to erase long-term audio level fluctuations, while doing so in a very unobtrusive manner. This sub-menu provides a few parameters that tailor the action of this.

Drive

The sets the audio level that enters the WB-AGC. Increasing the Drive will produce more compression. This control is calibrated between –6dB and +6dB, and adjusts the signal level into the Wideband AGC. It should be adjusted to net approximately 12dB of gain reduction with typical programming. Too little gain reduction can defeat the “leveling” function of the Wideband AGC. Too much gain reduction has little additional benefit. Nominal gain reduction values for the Wideband AGC are between 10 and 15dB.

Gate

When set to ON, it will freeze the gain at the last level of processing action that occurred before the audio signal fell below the threshold of operation. This control helps to minimize “pumping”, and the increase of background noise during pauses in programming.

Release

Controls the speed of recovery for any given amount of gain reduction. Faster action yields less dynamic range and the presence of more density to the audio. The Release control sets the time constants in relative terms using Slow, Medium, and Fast. Because the time constants are program-dependent, calibrating these controls in absolute time values (ms/dB) would be useless—therefore we use simple terminology.

Clicking Save after adjusting any of the parameters in this  will save the change and close the sub-menu.

Bass

This  contains the Bass EQ controls. In the the unique Omnia 3 signal processing architecture, these controls are placed in their optimal position — just before the multiband processor s. Each of the Deep Bass and Phat Bass controls can boost the level up to 12 dB. Be careful here not to overdrive the following s or over emphasize these lower frequency ranges. When used properly this specialized low frequency enhancement tools can deliver the thunderous bass and warmth that the Omnia is known for, and it can do so without making the sound muddy.

Phat Bass

A unique enhancement that adds filtered harmonics of the lower registers to the upper bass frequencies. The algorithm extracts information contained in the initial attack to do its work, and low frequency texture is therefore emphasized. Older recordings sound fuller (or phatter) with the added illusion of loudness. Phat Bass EQ also helps devices with small speakers sound like they have more bass than they actually do. A little of this effect goes a long way so be careful not to apply too much boost. Be sure to listen on several different types of both fixed and mobile media devices to arrive at a setting that works best for all of them.

Deep Bass

For those who demand thunderous bass, the Omnia 3 has it! Up to 6 dB of “thunder” can be dialed in. And we're not talking about a simple bass boost, but a rather sophisticated concept that takes into consideration the time alignment of the low frequencies as they pass through the entire Omnia system. It allows a loud, clean low end, with absolutely no sacrifice to the overall loudness of your signal. We won't tell you where the control is in the signal chain. But we will tell you that Deep Bass function is a shelf boost at 90 Hz, utilizing a phase compensated 12dB/octave slope to emulate the EQ function.

X-over

This  contains no adjustable parameters, but here's a bit of information about why we did what we did. Most multiband audio processors make a compromise in the crossover area in order to provide a flat dynamic frequency response. This is done to avoid audible peaks or dips in the recombined frequency response as the individual band gains change during processing. In an effort to minimize this problem, most processors use a fixed phase-offset in the crossovers. While such treatment helps to minimize frequency response peaks and dips, it also results in a loss of phase linearity, usually causing an increase in “smearing”, as well as reducing musical clarity.

In Omnia 3’s implementation, the crossover network is carefully time-aligned so that the recombined spectrum remains flat, regardless of the amount of gain control being applied within any band. This true phase linear response assures that harmonic overtones are not displaced in time. The result: the truer, more natural, and more musical Omnia sound.

Multiband AGC Sections

Similar in character to the wideband AGC described above, but expanded to three bands, this  has the ability to significantly add power and loudness to the audio while tailoring and pre-processing it for delivery to the final limiter . The system uses different algorithms for each of the bands: The low and mid bands use a feedback configuration, which produces a larger, warmer sound on lower frequencies. The high band utilizes a feedforward design that maintains a more open, natural and musical texture on higher frequencies.

As with any multiband processor, improper adjustment can exaggerate noise at high frequencies, particularly with older recordings that possess a good deal of tape hiss. This can especially occur if the highest AGC band is driven so that significant gain reduction occurs, and the band’s gating control is set to the lower end of the scale. During audio segments that have little or no HF content, the AGC will try to increase its gain in an effort to restore treble balance. Even during periods when the gate function is in the default Freeze mode, the problem might still exist with some programming.

Since the user parameters are the same for all three bands, only the LF Band will be detailed here.

Drive

Sets the audio level that enters the AGC. Increasing the Drive will produce more compression. This control is calibrated between –6dB and +6dB, and adjusts the signal level into the AGC. It should be adjusted to net approximately 12dB of gain reduction with typical programming. Too little gain reduction can defeat the “leveling” function of the Wideband AGC. Too much gain reduction has little additional benefit. Nominal gain reduction values for the AGCs are between 10 and 15dB.

Release

Controls the speed of recovery for any given amount of gain reduction. Faster action yields less dynamic range and the presence of more density to the audio. The Release control sets the time constants in relative terms using Slow, Medium, and Fast. Because the time constants are program-dependent, calibrating these controls in absolute time values (ms/dB) would be useless—therefore we use simple terminology.

Gate

When set to ON, it will freeze the gain at the last level of processing action that occurred before the audio signal fell below the threshold of operation. This control helps to minimize “pumping”, and the increase of background noise during pauses in programming.

Mix

This is where the three multiband processors are mixed together. Use care in adjusting this , as too much level from one particular band may cause an excessive amount of emphasis to that range of frequencies. Such adjustment may also drive the final limiter bands in that range of frequencies too hard, causing the sound to become unnatural, dense, and squashed. As explained earlier, if your desire is to “EQ” the sound, you should perform that function using the drive levels in the multiband . The mixer is primarily intended for minor “EQ” changes to the overall sound. There is a +/-6dB range of adjustment for each band.

Final Limiter

Omnia 3 employs a lookahead limiter to provide absolute and precision peak control. This limiter has been designed to minimize processing side-affects like IMD, which are usually associated with limiters of this type. Using an innovative design that cancels intermodulation products before they develop, allows this limiter to sound extremely transparent. The limiting function is derived using numerous control signals that monitor one another.

This type of peak controller is used instead of a clipper because it does not generate the same high levels of THD as a Clipper does. THD causes added difficulties in a coded audio system, as the harmonics generated from the clipping action, create added artifacts in the encoder. These are especially annoying at high frequencies.

On the other hand, a lookahead limiter, yields extremely low levels of THD, although it will create some IMD component, and this allows the audio coder to operate with minimal sonic artifacts. There are tradeoffs in how each of these peak controllers sound when they are set to produce added loudness. When a clipper is pushed, the audio may appear edgier. This is from the added harmonic content. In contrast, the lookahead limiter will appear busier, or dense as the action of the control signal may be heard, when more limiting is applied.

Limiter Drive

This is where the loudness versus quality is most evident! This limiter’s adjustment range is +/-3 dB, in 0.1dB steps. It is advisable to make minor changes, primarily as the “loudness fine tuner”. Be careful, there is a lot of power here! A little bit goes a long way!

Output

The peak output level adjustment is done using the individual Left/Right output controls. The control range is from –26dB to +6dB of gain. This level is normally set to the maximum input level, or just below it, of the device that the Omnia 3 is connected to.

Output Filter

For webcasting applications, especially at lower bitrates, it is sometimes desirable to reduce the audio bandwidth. This is particularly useful if you are using a low cost sound card to feed and external encoder as the filtering in many sound cards in inadequate.

A pull-down menu provides eight different filter response curves that can reduce the spectrum down to 4kHz.

Bypass

The processing can be bypassed simply by clicking on the BYPASS button located in the lower right hand corner of the processing panels. This is a simple and fast method to compare the before and after affects of the processing.

To save changes to the current processing preset and return to the main “Control Panel” screen, click “Save”. Click “Cancel” to return without saving changes.