Musicam RoadRunner™
 
 
 

Your EDnet supplied Musicam RoadRunner is compatible with a number of MPEG Layer II and Layer III, as well as G.722 audio codecs, bringing with it a certain degree of complexity in configuration. The purpose of this document is to provide clear, concise instructions for the set up of both your RoadRunner and other compatible codecs. To fully understand the capacity of this device, the complete manual is recommended. Nevertheless, a good grasp of this guide should facilitate day to day operation.

I. RoadRunner Specifics

A) General Configuration Issues

Like all ISDN gear, the RoadRunner's terminal adapter requires certain configuration info specific to the attached line. This includes switch protocol, directory numbers, and SPIDs. If EDnet has provided your telco line as well as your RoadRunner, then most likely we've taken care of this for you and you're ready to plug and play. Should the RoadRunner need to be reconfigured (e.g., when placing it on a different ISDN line) use the [TA 301] menu option.

As outlined in on pages 36-37 of the RoadRunner manual, Musicam provides a slate of Quick Configurations, which are essentially a set of speed dials that configure the unit but do not place calls. An excellent tool, these Quick Configs should not substitute for a clear understanding of all relevant parameters. That said, this feature can prove invaluable when connecting to a site not well versed with their unit's operation. For a snapshot of how the unit's audio parameters are currently configured, use the [Status] menu option. This will report algorithm type, bit rate, sampling frequency, and whether calls are connected on the respective B-channels.

B.) Menu Navigation Basic menu navigation is accomplished by the left most column of keys. The top (?) key brings you up the menu tree, the middle two (?????? keys move you horizontally within a given menu level, and the bottom (Enter) key both moves you down the menu tree and, if at the root level, invokes a parameter change. Note that, while manipulating horizontally across a given root level, the current setting will remain in parenthesis and the potential new setting will be in brackets. The ??will get you out of the "Status" screen.

C.) Transmission Modes 1.) MPEG Layer II
Uses perceptual coding techniques to achieve compression factors of about 6-8:1, dividing the frequency spectrum into 32 bands. The frequency response is 20Hz-20kHz in ÔCCS 2-line' mode, utilizing both ISDN bearer channels (B-channels); and 20Hz to approximately 9kHz in "1-line" mode (one B-channel).


2.) MPEG Layer III
Employs the same general perceptual coding scheme as Layer II, but divides each of the 32 frequency bands into 18 sub-bands, for 576 total bands. Uses only a single B-channel, achieving compression factors of about 12:1. In Layer III the sampling frequency can be set to either 48kHz for 20kHz frequency extension or 32kHz for 15kHz frequency extension.   (Tip: EDnet recommends that when using Layer III mode that you utilize the 32kHz setting. We find that audio quality is questionable when attempting full bandwidth transmissions in Layer III.)


3.) G.722
An algorithm with extremely short delay time, popular for remote broadcasting feeds. Uses one B-channel for 7.5kHz of top end. If a site has a Comrex codec, it's probably G.722.

D.) Operation Menu Allows you to configure the encoder section of the codec manually rather than loading a Quick Configuration. This menu walks you through a "set-up sequence" where you'll be prompted to enter the following:


1.) Algorithm
Sets the algorithm type (e.g., MPEG2 or MPEG3).


2.) Sample Rate
MPEG Layer II only supports a 48kHz sampling frequency. Other valid sample rates include 32kHz for MPEG Layer III and 24kHz for use with a Musicam CDQ1000 (see ÔGeneral Compatibility Issues').


3.) Bit Rate
Scalable from 56 to 128 (kb/sec). In most applications this should be set at 112 or 128, depending if the session will be at 56 or 64 per B-channel.


4.) Line Format
Determines the number of Ôlines' (B-channels) that will be employed. "CCS 2-line mode" is the highest quality setting, meaning that the two B-channels are being aggregated together to form the data stream. E.) Advanced Menu Although few scenarios will necessitate use of this menu option, it contains one important parameter known as "Independent," which provides compatibility to certain other codecs. For more on this setting, see sections III (A3) and IV.

(Tip: Some Layer III Quick Configurations don't properly set "Independent" to yes. It may be necessary to manually set this parameter to yes despite the fact the RoadRunner reports that the Quick Config has already done so.)
 

II. RoadRunner Controls/Connectors



A.) Front Panel
  1.) Inputs
Two "microphone level" inputs are provided on the front panel along with knobs to adjust the gain. Note that the RoadRunner does not supply "phantom power," a 48V signal that many mics require to operate. If you plan to plug such a mic into the RoadRunner then you'll need an external microphone "pre-amp" or "power supply." If you aren't using these mic inputs be sure that the gain knobs are fully counterclockwise. The "Input 3" knob sets the gain for the third input jack (see "Rear  Panel").

(Tip: It is critical that any microphone input you don't use have its gain knob turned all the way down. Otherwise an unacceptable level of noise will be added to your transmission.)


2.) Monitor Outputs
Two headphone inputs, along with corresponding level controls, are provided. The "Local" knob will bring the audio signal being presented to the RoadRunner to the headphones; the "Return" knob will bring the signal received from the far end codec to the headphones.


3.) LEDs
The Norm light should come on frequently when presenting input signal. The Clip light, by contrast, should come on only occasionally during peaks. The On Line light has three distinct states: (1) OFF, indicating no calls are present; (2) FLASHING, indicating one or two calls are present but the unit isn't "locked" to the far end codec; (3) SOLID, indicating not only are call(s) present but that the unit is "locked" to the far end codec. In order to receive far end audio, the On Line light must be in this condition.

B.) Rear Panel

1.) Line/Mic Input
A 3rd input is provided on the RoadRunner's rear panel, switchable between mic and line level. The gain for this input, labeled "Input 3," is on the front panel.

IV. Compatibility With Other Codecs

A.) CCS CDQ2000
This codec does MPEG Layer II only. All four CDQ2000 "line select" switches must be in the down position, and its the large silver knob should be at either 112 or 128, depending on whether the individual B-channels are dialing at 56 or 64k. If an EDnet site, you'll typically need "Independent" set to "yes". The matching setting on the CDQ2000 is on the unit's rear panel on the bottom row of dip switches. Dip switch 6 up = Independent YES; dip switch 6 down = Independent NO.