Field Report: Tieline Bridge-IT

February 1, 2012


When better-than-phone quality is needed, or a new STL is to be installed, IP is discussed more and more. In the case of the Flames Sports Network we chose the IP route for college football and basketball broadcasts, and we're relying on the Tieline Bridge-IT to get us there and back.

Tieline Bridge-IT

Bridge-IT fits into one half of one rack space. It has an LCD display and a complement of buttons and keys, making it fully configurable from the front panel. The LCD screen displays the navigation menu tree and PPM metering of input and output levels. The back panel houses XLR jacks for dual-channel analog and stereo AES3 in/out. A 1/4" jack allows for local headphone monitoring. A Phoenix plug facilitates closure contacts. Programming data is connected through USB and RS-232 jacks. A standard LAN connection is available with connection and traffic indicator LEDs. The 1A rated power supply is a typical wall-wart providing 12Vdc.

Oooey GUI

Local control and programming is done using the front LCD display, which features an easy-to-navigate menu tree. The front panel is useful in that sometimes Web browser GUI control isn't readily available. In our experience, the GUI is used mostly for remote troubleshooting and monitoring. Most, if not all our connection procedures are achieved using the front LCD screen. Bridge-IT is also controlled via an Internet GUI. Most of the configuration features are accessible using the GUI, including primary connection and monitoring settings. The codec is controlled via USB connection as well.

While the front LCD panel on the Bridge-IT is a straightforward control feature, the Web-based GUI is a friendly navigational and control interface. Assuming the user's computer has network access to the codec, and Java is enabled, simply entering the Bridge-IT IP address will launch the GUI. The codec can be set for DHCP or static IP address configuration. Once inside, several on-screen panels display input and output audio levels, connection speed dial and contact lists, connection status and many other features.

Audio hook up and control

Audio input levels (analog or AES3) are adjusted via the front panel or GUI with the key feature being the 18dBu of available headroom. Simply put, input levels peak at +22dBu, making clipping difficult. The analog inputs can be adjusted to line level or microphone level to accommodate different inputs. Bridge-IT can also be set to accept unbalanced connections. 15V phantom power is also available. The AES3 inputs can accept 32kHz, 44.1kHz and 48kHz sampling rates. Additionally, the codec features Intelligent Gain Control (IGC), which controls audio peaks and transient levels. The linear response of the IGC can work automatically or be fixed. The IGC works transparently, ensuring proper level control throughout a dynamic broadcast.

Performance at a glance
◊ XLR digital and analog I/O
◊ Control via front panel or GUI
◊ QoS Performance Engine manages network errors
◊ 29 broadcast audio algorithms
◊ RS-232 data control and relay closures

The unit ships with 29 broadcast-quality algorithms, the selection of which is based upon available bandwidth and IP connection quality, and the material being broadcast. MP2, G.711 and G.722, and PCM can be configured for stereo or mono broadcasts with bitrates ranging from 16kb/s to 1.54Mb/s. AAC and Enhanced Apt-x algorithms are additional licenses available. Bridge-IT features "Music" and "Music Plus" which are proprietary Tieline algorithms that allow for minimal bandwidth usage while providing high quality audio. Depending on program material, very low bandwidth connections can facilitate surprisingly pristine audio with little or no artifacting.

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Traffic issues

When public data routes carry critical broadcast audio, care and planning must be exercised in knowing how IP gear will behave. By way of preparing for heavy network traffic, auto jitter adapter, fixed buffer level and forward error correction (FEC) can be configured when lost data packets compromise broadcast quality. Auto jitter adapter is adjusted by buffer priority, meaning Bridge-IT will introduce latency to make up for lost or late packet delivery. Each auto jitter setting is a compromise between delay and audio quality. The codec will make necessary adjustments based on how the priority is set.

The user can set a fixed level buffer, which prescribes the amount of latency on the audio stream. The delay is constant at all times. Forward error correction uses more bandwidth, but it allows Bridge-IT to duplicate a certain percentage of the audio stream to account for lost data packets. In situations where bandwidth is limited, FEC can make the situation worse, so use caution. FEC is recommended for connections that have plenty of data headroom, but lose packets occasionally. Packet and stream data and connection statistics can be monitored via the web GUI or front panel.

Bridge-IT also features QoS settings, where data packets can be instructed for different prioritization through several different networks. This is achieved by changing the DSCP field in the data packet header. IT administrators should be contacted when using the QoS settings. The codec uses "line quality" readings to monitor connection stability. "L" shows the quality of the local connection. "R" indicates network behavior on the remote end. A reading of 99 on both ends is optimal.

Contacts list

Sometimes a single Bridge-IT connects to several remote Bridge-IT units or other codecs for differing purposes. When this is the case, the GUI is useful for storing lists, programs and contacts previously set up by the user. Creation of programs allows for one-button dialing to other units. For example, a remote talk show studio may connect to a network master control each day. Instead of having to enter the IP address, algorithm, connection type, bit rate, jitter buffer and several other settings each time, a program can be configured with a contact. This allows for quickly calling another codec.

Sometimes a single Bridge-IT connects to several remote Bridge-IT units or other codecs for differing purposes. When this is the case, the GUI is useful for storing lists, programs and contacts previously set up by the user. Creation of programs allows for one-button dialing to other units. For example, a remote talk show studio may connect to a network master control each day. Instead of having to enter the IP address, algorithm, connection type, bit rate, jitter buffer and several other settings each time, a program can be configured with a contact. This allows for quickly calling another codec.

Tieline
◊ 888-211-6989
www.tieline.com
sales@tieline.com

In the event the codec is being used as an STL, and the connection is lost for an extended period, an SDHC card loaded with music or special messages can be inserted in the receiving Bridge-IT. The codec will begin playing the MP3 files until the audio stream is restored. This prevents dead air situations if IP connectivity is lost.

In an era of exploration that puts our valuable audio chains on the public IP infrastructure, having robust gear to navigate is vital. Bridge-IT is smart and concise in its operation. It negotiates difficult networks well, and makes up for costly data packet errors. It takes up very little space in equipment racks, and it travels unbelievably well. The front screen LCD display and buttons provide quick, on-the-fly operation, meaning everyone from seasoned engineers to new sportscasters can use Bridge-IT to accomplish fantastic remote or STL audio connections.


Wygal is the programmer and engineer for Victory FM at Liberty University, Lynchburg, VA.



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