Eisenhamer Engineering

Tieline Codec IP Broadcasts

Original notes on IP broadcasts with Tieline codecs.
(update coming soon)

IP Codec Notes

It takes much testing to get the right "balance" between quality and usability.  The balancing act for this are the data rate and the jitter buffer and FEC (Forward Error Correction).  The codecs default to a jitter buffer of 500ms.  That is a 1/2 second from remote to station and a 1/2 second from station to remote location.  For interactive shows this can become a bit troubling.  Take time to find the right balance.

How?  Remember that the internet is a cloud of uncertainty.  Know your equipment and its limitations.  If using Music mode on your G3, which we most always do, note that the encoding of the audio takes an impressive 70ms.  That is fast compared to other encoding schemes.  Next is that "cloud".  Run a Ping from a computer and get a feel for what latency will occur through the internet.  Do not be surprised at some of the numbers you find.  Start with an FEC of 20% just to help things along.  Bandwidth is your friend and enemy.  As an example we successfully ran 16 hours over IP with an iMixG3 setting of 64kbps, 200ms jitter buffer, and 20% FEC.  A good trick:  Press the MS knob while connected and scroll down to the actual jitter buffer reading, then pick a jitter buffer setting that is slightly higher than the highest reading shown in the window.

Also remember what your download capabilities are at the station/studio.  Tieline recommends attaching each codec to its own DSL line.  That is good advice unless you are at the end of a CO (central office) run and the maximum data rate is 384kbps.  That is maximum.  Reality is slower, so beware.  We are about to install a T-1 that will feed both our G3 rack mount gear.  The chances of us running both simultaneously is slim, but not improbable.  This will give us easily 500kbps upload even if both are used; and being that the maximum rate of a G3 is 384kbps we will have room to spare!  The fact that it will not fight with our normal day-to-day network traffic makes this a real winner.  I will report on our success in the blog.

The Toolbox

I will fill you in on some stuff to make configuring your Tieline gear a bit easier to understand.  Remember that the folks at Tieline are very helpful and friendly.

Learn how to use the Toolbox. I have many profiles configured for the different venues that we visit. Most of these profiles are for existing ISDN lines and certain working settings for IP locations where either a static address is required or a certain bit rate works better than others.

Note: This was written some time ago. I plan on updating this informtion. Some items that have been improved by Tieline Technology is the encoding. Their Music Plus mode is quite amazing sounding with the customary 70ms encoding time which still beats ACC-LD. In addition we are learning more about IP and IP broadcasts. With this information we are quite happy with our results.