All-In-One Hardware Solutions | Streaming Audio: The FezGuys Guide

A handful of expensive hardware tools do the work of most of the processes described earlier, all in one package. These hardware boxes do the job well, but they are only appropriate to those with corporate budgets, a friend in the business, or in dire need. Both units (the Orban 6200S and the Telos Omnia 3-net) come from companies with long experience in the traditional terrestrial broadcast medium.

Using the Orban 6200S

This high-tech $5,000 1-U rackmount box is primarily a digital audio preprocessor for the audio side of digital television transmission. Orban also markets the 6200S as a Webcasting audio optimization tool. Many of the more arcane broadcast features of this unit won't be used in the typical Webcasting environment. Using the 6200S to optimize live audio for low bit rate real-time streaming requires only basic in/out processing. That processing, however, is of a high quality, providing an FM-broadcast style sheen to your stream.

NOTE

Orban also offers a more affordably priced PCI card that gives your Windows computer the functionality of the Optimod 6200S. See www.orban.com for more information.

The weighty manual includes schematics and parts lists. You can install and use the Windows-based remote control software (with a serial cable connection) to configure and maintain your 6200S from your authoring computer.

The front panel has a screen display with four soft key buttons below a small screen, which provide access to functions and controls. Additional flashing Next and Previous arrow buttons are used to horizontally scroll the screen and accommodate menus that cannot fit in the available display space. A large control knob makes changes to settings. Parameter settings are adjusted by holding down the appropriate soft key and simultaneously turning the control knob. A Recall button recalls any of the unit's factory or 32 user presets, and a Modify button edits those presets. A Setup button accesses the technical parameters necessary to match the 6200S with your broadcasting system. An Escape button returns you to previous menu levels.

Front panel input meters show peak input level for digital or analog inputs (referenced to "0 = digital full-scale"). An automatic gain control (AGC) meter indicates the gain reduction of the slow two-band AGC (with Orban's patented bass-coupling system) processing preceding the multiband compressor (with 25dB full-scale gain reduction). A Gate LED shows gate activity. The Gain Reduction meter shows gain reduction in the five-band multiband compressor. Limiter meters show the amount of look-ahead peak limiting in the left and right channels (with 12dB full-scale gain reduction).

This book uses the 6200S as an audio optimizer for authoring a low bit rate live stream (as described in Chapters 3 6). Make sure you have all the cabling and adapters necessary to hook up your mixer (or other audio source) to the Orban and from the Orban to your authoring computer.

Connect your live stereo audio signal into your mixer. Connect the mixer's outputs to the XLR stereo analog inputs of the 6200S. The optimized signal is sent from the analog Monitor XLR stereo outputs of the 6200S to your authoring computer. Your authoring computer will be running an encoding tool authoring a live stream for 56K dialup modems. As always, it's best to begin from factory default settings.

NOTE

The recommended configuration (for the highest quality audio) for the 6200S uses the digital AES/EBU connectors. Because this book is geared toward new streamers who probably don't have a sound card with digital inputs installed in their authoring computer, this particular Step-by-Step tutorial uses analog input and output. Regardless of whether you use analog or digital input, the Orban 6200S operates both digital and analog outputs simultaneously. Follow the instructions in the manual if you plan to use digital in/out.

STEP-BY-STEP: Using the Orban Optimod 6200S to Optimize Your Audio

Connect your audio source into the analog XLR input of the 6200S.
Connect the output of the 6200S to your authoring computer's input.
Press the Setup button to access the Setup Screen, and press the Next arrow button to access miscellaneous Setup parameters.
For MAX LPF (Low Pass Filter), leave the default of 20.0kHz.

NOTE

Advanced users who know that the sample rate of their encoded stream is lower than 44.1kHz should set MAX LPF to approximately 45% of that sample rate. This allows the Orban to do a better job optimizing its audio. Using the encoder tool to find out a stream's individual sample rate settings might require some digging. You advanced users can handle it!
For ST CHASSIS, leave the default of No unless you're using another automatic gain control device elsewhere in your audio pathway.
Leave MONO/ST (mono or stereo) at the default Stereo setting. This allows the encoder to make the choice of whether to convert to mono.
Press the Prev arrow button to return to the first page of Setup options, and press the soft key under I/O CALIB to calibrate your input and output levels.
Start your source audio.
Press the soft key under ANLG IN CALIB.
1. Make sure that INPUT is set to "analog."
2. Adjust the AI CLIP by selecting the loudest portion of your source audio so that the program peaks at approximately 10dB on the Input meters. This calibration is most important to the optimal efficiency of the 6200S. Spend the necessary time getting this level correct. Keep an eye on those meters and adjust accordingly.
3. Adjust the AI REF VU level to approximately 10.0 on the AGC meter. Watch for a slight delay in the AGC meter adjusting after you change the value. This is because the AGC needs to listen for a moment before it decides on the appropriate level. Observe the AGC meter for a little while to make sure that AI REF VU is set correctly.
Press the Escape button and select the soft key under the ANLG OUT CALIB. Verify that MON OUT is set to Post Lim, and if it is not, change it.
Press the Escape button repeatedly to return to the top level.
Press the Recall button and use the big knob to scroll to TV 5B-GEN PUR W/NR. Select this preset from the preset menu. These presets are based on an anticipated format of a station.
To activate the preset, press the soft key button under RECALL NEXT. The preset you have just chosen is now active. The 6200S is processing your source audio and feeding it into your authoring computer's input.
Press the Modify button to modify the setting.
Press the soft key under LESS-MORE and tune between 1 10 to your preference. Increasing this setting reduces the dynamic range of the output audio by increasing the volume of the quieter sections of your source audio. Crank it to 10, listen, and back off as necessary.
Press the Escape button repeatedly to return to the top level. The main page now displays your preset and modif prefix for the on air (currently active) preset. Your selected preset will be displayed after the on air: label. Because you modified the preset, the text modif will be displayed before your preset. A SAVE PRESET option will be available for you to save your changes to a new preset.
Set your authoring computer's input signal appropriately and continue the encoding process as noted in Chapters 3 6.

The configuration outlined in the Step-by-Step is based on your subjective taste as a good starting point for a 56K modem stream of music in any format. If you're working with voice only, try the TV 5B-NEWS preset as a starting point. Many other customizable audio optimization settings are available within the 6200S. Advanced users can play with configuring the equalizer and FULL CONTROL settings (available by pressing the Modify button).

The manual for the 6200S includes a detailed description of what each preset does as well as extra information about the acoustic properties of this kind of industrial-strength audio processing.

NOTE

When using the 6200S to optimize high bit rate streams, you might want to use the PROTECTION presets as your starting point. Check the manual for information on these presets, designed for the highest possible fidelity.

The Orban 6200S is an audio optimization tool of choice for the big television and radio broadcast networks. It uses industrial grade materials, architecture, and software, and because of its ubiquity within the industry, the Orban 6200S is part of the reason for the current state of broadcast (TV, FM, and AM) audio quality. Tools like the Orban, increasingly efficient compression technology, and faster Internet connectivity to the home are all helping the state of streaming audio quality approach broadcast standards.

Using the Telos Omnia-3net

This unit is a digital audio preprocessor specifically designed to optimize source audio prior to streaming audio encoding. The Omnia-3net is based on the Omnia-3FM, a terrestrial broadcast preprocessor.

The 2-U rackmount box (less than $4,000) has a simple and functional design. Besides the display screen, it has two interface controls on the front panel: a push button and a jog wheel. The push button toggles the display between menus and bar graphs. These vertical bar graphs display input and output levels. Turning the jog wheel displays current gain reduction levels. The jog wheel is primarily used in the menu mode to select menu items and to change various parameter values. Pressing the jog wheel selects the highlighted menu item or accepts the current parameter value. This is a commonsense interface that's easy to operate.

On the back panel are AES/EBU digital and analog stereo XLR input and output connectors. The internal PC card holds software as well as user and factory presets. An RS-232 serial port connector is available if you want to use optional Windows software on your computer to configure the Omnia. Advanced users can use many other features, such as Daypart Automation to set and schedule program-level changes.

The manual is much more than a dry laundry list of settings. Using common English to describe technical processes, the manual provides an informed layman's grasp of relevant issues, continually reminding the reader of the larger audio/broadcast/streaming implication behind each parameter modification. The manual even includes a single-page Menu Tree with a flow chart detailing the location of every menu option. Telos is passionate about its technology, exhorting the reader to carefully take advantage of the many features of the Omnia-3net, and going so far as to recommend the amount of time to spend configuring the unit to appropriately work within a given system.

In this Step-by-Step tutorial, you'll optimize a live stereo audio signal for a low bit rate 56K live stream.

STEP-BY-STEP: Using the Telos Omnia-3net to Optimize Your Audio

Connect your audio source into the Omnia's input (either AES/EBU or analog XLR). This example uses the analog input.
Connect the Omnia's output to your authoring computer's input.
Start your source audio.
To set the Omnia to use the analog input and outputs, go to the main menu and use the jog wheel to select and enter the Input & Output menu.
1. To set the Omnia to use the analog input, use the jog wheel to scroll to Input Source and verify that ANALOG is chosen. If necessary, select ANALOG.
2. For Mono Mode (setting the number of channels), leave the default of Stereo and allow the encoder to convert to mono, if necessary.
3. For LPF Freq (Low Pass Filter), change the default values of 16kHz to 22kHz. This is necessary because some formats (such as QuickTime) use 44.1kHz even at 32Kbps.
  
  NOTE
  
  The LPF Freq setting is only mentioned in documentation about the Omnia-3am (an only slightly different configuration of the Omnia than the 3net used here), so it is assumed that this is a standard low-pass filter. For that reason, the highest LPF Freq setting is chosen to allow for encoders that encode up to 44.1kHz. Choose the maximum setting of 22kHz so that the encoder has access to the full frequency range that the Omnia supports. Advanced users who know that the sample rate of their encoded stream is lower than 44.1kHz can set LPF Freq to approximately 45% of that sample rate to prevent aliasing distortion. This allows the Omnia to work more efficiently. Using the encoder tool to find out a stream's individual sample rate settings might require some digging. You advanced users can handle it!
4. Use the jog wheel to scroll to and enter the Input Levels menu. Because you're using an industry standard mixer to send your feed into the Omnia, you shouldn't need to adjust the Omnia's default input level settings of 10dB. Your mixer should be sending at +4dB. Tune the mixer's master level as loud as possible without clipping. If you're sending a stronger or weaker signal, adjust the Omnia's left and right inputs accordingly. After you've chosen a setting, check your levels by pressing the front panel button to toggle between the bar graphs and level settings.
  
  NOTE
  
  Earlier manuals for the Omnia-3net refer to an Analog Gain menu option to control the input level. This option has been removed in recent units. If your unit has this option, then read the manual about how the earlier process will differ from this description.
5. Use the jog wheel to scroll to and select the backward arrow to return to the Input & Output menu, and then enter Output Levels. The system default of +4dB should be fine. Unless severe level disparities are present, it's preferable to use the default output level and adjust the authoring computer's input level. Use the jog wheel to scroll to and select the backward arrow twice to return to the main menu.
Use the jog wheel to select and enter Audio Processing, which places you in the Preset menu.
To select a preset, use the jog wheel to select and enter Select Preset. For your 56K modem stream, choose Lo-BR-Aggr (for "low bit rate aggressive"). The Omnia is now optimizing your audio signal for a 56K live stream. Advanced users can enter Edit Parameters from the Preset menu to modify the selected preset from its default values. Numerous options allow you to fine-tune (or ruin) your audio, depending on your skill and patience. Also from the Preset menu, the Save to Card As function allows you to save the preset with any modifications to the internal PC card.
Set your authoring computer's input signal appropriately and continue the encoding process as noted in Chapters 3 6.

The Lo-BR-Aggr preset used in this Step-by-Step is one of five factory defaults included with the Omnia-3net. It was selected based on the authors' subjective listening for a 56K modem stream of music in any format. You might find any one of the other modifiable factory presets (Lo-BR-Lite, Lo-BR-Aggr, Hi-BR-Lite, Hi-BR-Mod, or Hi-BR-AGGR) more to your tastes.

These factory presets are based on the Omnia engineers' long experience with coded and compressed audio. More advanced users can use them as a starting point. Uneducated modifications of the presets can make things worse, however. Refer to the manual for details on configuring the specific components of each preset.

For more information on preprocessing audio for streaming, refer to the White Paper "Audio Processing for Digital Audio Broadcasting and the Internet" (see the Appendix for Web site URL).