Your EDnet supplied Zephyr is compatible with a variety of Layer II and Layer III audio codecs, yet with this sophistication comes a degree of complexity in configuration. The purpose of this document is to provide clear and concise instructions for the configuration of both your Zephyr and the most common compatible codecs you may run into. For more detailed operation instructions and discussion of the compression process please refer to your Zephyr manual.
1. General Compatibility Issues
Regardless of what kind of codec you're connecting to, there are some common issues that need to be addressed, preferably before the session takes place. As most common codecs offer several mono and stereo modes, both sites should be aware of what mode will be used for the session. This is especially important when connecting to another Zephyr in Layer III mode. The transmit mode on one end must be the same as the receive mode on the other end for the units to function. Layer II operation is a bit simpler in this regard, however, you should still go over the mode descriptions presented here to ensure optimal quality for the type of session you're doing.
The second important issue common to all codec types is the data speed used by the codec. In the US, ISDN lines are commonly used for both 56k and 64k calls. Prior to ISDN being widely available the common data service was 56k, and that rate is still the most widely used as it's guaranteed to work to all locations. Using a 64k data rate will give you slightly higher transmission quality, however, and you may find some sites that use 64k primarily. Layer II codecs often use two 56k or 64k calls to provide full audio bandwidth, so you may find some studios who say their rate is 112k (2 * 56) or 128k (2 * 64). On your Zephyr you must specify the per-channel bit rate, so you would set it to 56k for a 112k Layer II connection or 64k for a 128k connection. Here are step by step instructions for changing the mode and rate - guidelines for selecting the proper mode are presented in section 4.
1. Press the HELP key twice to return to the main status screen.
2. Press the UTIL key once to go to the main utility screen.
3. The transmit mode (XMT) should be bracketed, indicating it is selected. If it's not bracketed, use the arrow keys to select it. If it's not on the screen, hit HELP twice to take you back to the status screen and hit UTIL to go to the main utility screen.
4. Press the NO key to toggle through the various modes (i.e. L3 Dual, L2 JSTEREO) . When you've reached the desired mode, press the YES key.
5. Use the down arrow to go to the receive mode (RCV). Again press the NO key to toggle through the available modes (i.e. L2, L3 MONO) and press YES to select the desired mode.
6. Use the down arrow again to go to the rate and change it using the NO key toggle through the various combinations and the YES key to store the selection. The first number (56k or 64k) is the data rate, the second number is the audio sampling rate. If you're using a Layer II mode, you'll be restrained to a 48kHz sampling rate.
7. Press HELP twice to return to the status screen.
2. Layer III Operation
The Layer III algorithm was designed to provide high audio quality at relatively low data bit rates. Using Layer III, a 15kHz mono signal can be attained on a single 56k call; discrete 15kHz stereo is possible with two calls. If you're doing a session with another Zephyr you'll usually be in Layer III. As quite a few Zephyrs don't have the Layer II option installed and are only capable of Layer III, you're guaranteed compatibility with these units by using Layer III. Another characteristic of earlier Zephyrs is that they only offer an audio sampling rate of 32kHz, yielding a 15kHz audio frequency response. You'll see on your Zephyr that if you press the UTIL button to access the utility menu you can change the rate. This setting toggles between the available bit rates (56k and 64k) and audio sampling rates. (32kHz or 48kHz). On your Zephyr you can set either a 32kHz sampling rate or a 48kHz sampling rate, however you'll have to be set to the same sampling and bit rates as the other unit. If it's an older Zephyr, you'll need to be at 32kHz. Even when both of you can select a 48kHz sampling rate, if you absolutely don't need a 20kHz audio bandwidth you'll have better quality using a 32kHz sampling rate. This is because by increasing the sampling rate, you increase the audio range that has to be compressed, therefore requiring more data compression on the audio, which can lead to more artifacts. As the Layer III algorithm only uses 56k or 64k for each audio channel, any reduction in the audio bandwidth will lead to fewer artifacts, and 15kHz is fine for most applications. If you do require 20kHz, we recommend using a Layer II mode.
You'll notice you can set both transmit and receive modes. These can be different, but must match the complementary mode on the other end for the units to communicate. For example, you could send stereo material to the other end, in which case you would be set to L3 JSTEREO for transmit and they would be set for L3 STEREO for receive, while they sent you mono program by having their transmit mode set to L3 DUAL and your receive mode set to L3 MONO. Here are guidelines for which modes to use for various session types. Refer to the Zephyr manual for a more detailed description of the modes.
Mono transmissions - use the L3 DUAL mode for the transmit side and L3 MONO mode on the receive side. Only one call is required, however you may wish to feed both channels with the same mono source and use the L3 JSTEREO transmit and L3 STEREO receive modes with two calls to provide optimal bandwidth.
Stereo audio transmissions - use the L3 JSTEREO mode for the transmit side and the L3 STEREO mode on the receive side. Two calls are required. Note that if you have a mono only Zephyr unit you can still receive in Layer II and Layer III stereo modes. Only transmission is limited to mono.
Discrete two channel material (i.e. TC on one channel) - use the L3 STEREO mode for the transmit side and the receive side. Two calls are required.
3. Layer II Operation (to EDnet codecs)
You'll use the Layer II modes in the Zephyr with other EDnet MPEG/128 (Digital Patch) sites and with a variety of other codecs. Unlike with the Layer III modes, there's only one Layer II receive mode (L2), so setting modes is a bit simpler. Once again, the receive mode must correspond to the transmit mode on the other end for the link to work. (i.e. if you're set for L2 receive and they're set for a Layer III transmit mode, it won't work). Layer II has been optimized to work at slightly higher bit rates than Layer III and you may find mono transmissions will sound better with the L2 MONO128 mode, which uses two data channels, than with the L3 DUAL mode. Note that the Layer II discrete two-channel mode only provides an 8-10k frequency response, so if you need to run timecode with your audio and the other end has a Zephyr, you'll want to use a Layer III mode. The L2 JSTEREO mode offers an 18kHz audio bandwidth, but isn't discrete stereo. See the Zephyr manual for a more detailed explanation of the modes. Here are Layer II guidelines:
Mono transmissions - use the L2 MONO128 mode for the transmit side and L2 on the receive side.
Stereo audio transmissions - use the L2 JSTEREO mode for the transmit side and L2 on the receive side.
Note that if you have a mono only Zephyr unit you can still receive in Layer II and Layer III stereo modes. Only transmission is limited to mono.
Discrete two channel material (i.e. TC on one side) - use the L2 DUAL mode for the transmit side and L2 on the receive side.
4. Compatibility With Other Codecs
Make sure to verify what bit rate is to be used prior to the session. If you're unable to find out in advance, try 56k first unless it's an international site, in which case try 64k first.
The following outlines the steps necessary based on the most common configurations of the codecs specified. If you are unsuccessful after following these instructions, contact EDnet at +1 800 933-3638.
CCS CDQ2000 and CDQ Prima (EDnet MPEG/128 or Digital Patch) - For operation with EDnet CDQ sites, you need only select the appropriate mode for the session as outlined above.
CCS CDQ2000/2001 (non-EDnet) - For use with non-EDnet CDQ2000/2001, if it's a send/receive unit or a receive only unit, the other end will have to make a slight configuration change. No change is necessary on send only units. On the back of their unit are two rows of DIP switches (one row if receive only). On the lower row of DIP switches, switch 6 must be up for operation with the Zephyr.
On the front of their CCS unit, the Line 1 and Line 2 Select switches should be down on both the Encoder and Decoder and the bit rate knob should be at 112k or 128k, depending on whether you are calling at 56k or 64k.
On the Zephyr, select the Layer II mode (L2 MONO128, L2 JSTEREO, etc.) appropriate for the session as outlined above
CCS CDQ Prima - Non EDnet Prima sites will need to change one parameter in the Decoder section. From the front panel they should press the DEC menu button, select Indep , press ENTER, select YES, and press ENTER again. They'll also need to be in CCS 2 Line mode at either 112k or 128k.
CCS CDQ 1000 - The CDQ1000 is a single line 56k or 64k codec offering both MPEG Layer II and G.722 compression. The two modes on the CDQ are selected via front panel switch. Your Zephyr is compatible with both modes.
To use Layer II, select the L2 MONO transmit mode and the L2 receive mode on the Zephyr. On the CDQ 1000, DIP switch 7 should be in the down position and the audio sampling rate will need to be at 48kHz.
For G.722 operation, select G.722 for both transmit and receive.The audio frequency response of the CDQ1000 is limited to about 8kHz.
RE: - This unit should be compatible at 56k or 64k, but we haven't been able to test yet.
MPR LII Blue - This unit should also be compatible, but we haven't been able to test yet.
Comrex DXP-1 and DXR-1 - These are both G.722 codecs and offer an 7.5kHz audio bandwidth on a single call. Select G.722 for both Transmit and Receive modes on the Zephyr. These codecs are also capable of 15kHz audio when used with another Comrex. Should you desire the added quality we can bridge you through EDnet.
CCS Micro56 - Select G.722 for both Transmit and Receive modes on the Zephyr.
Other G.722 Codecs - All G.722 codecs should be compatible with the Zephyr if G.722 is selected for the Transmit and Receive modes.