Most Popular Articles
Establishing a SIP Connection
For two codecs to successfully communicate via SIP through a SIP server, information must be exchanged between the two devices. Codecs manufactured by members of the Audio-via-IP Experts Group are SIP compliant. These manufacturers include AETA, Mayah, Oban/CRL and Tieline.
When one codec attempts to communicate with another via SIP, the two units begin the negotiation process shown in the figure.
Codec 1 first suggests an audio encoding algorithm, sampling rate and coding rate, such as MPEG Layer 2 at 48kHz and 384kb/s. Codec 1 can also suggest an alternate encoding method, such as MPEG layer 3 at 44.1kHz and 256kb/s. Codec 2 is unable to use Layer 2 audio, so it selects the alternative (Layer 3) by responding with those settings. Codec 1 acknowledges the chosen algorithm by transmitting an ACK signal. The two devices are then connected via the Layer 3 option.
It is common for a device to offer several options of encoding to ensure that a connection can be established. The SDP portion of the SIP message carries this information, and the choices are offered in an order of priority for the receiving codec to choose.
Acceptable Use Policy blog comments powered by Disqus
[an error occurred while processing this directive]
Today in Radio History
The history of radio broadcasting extends beyond the work of a few famous inventors.
EAS Information More on EAS
The feed provides feeds for all US states and territories.
Need a calendar for your computer desktop? Use one of ours.
Information from manufacturers and associations about industry news, products, technology and business announcements.
When Northern Community Radio set out to build a new community radio station in rural northern Minnesota 38 years ago, naysayers said that it would be broadcasting “only to a bunch of gophers
Browse Back Issues[an error occurred while processing this directive]
Also in the July Issue
- Trends in Technology: Robust IP STL
- LPFM on The March
- RF Engineering: Modern Modulation Techniques
- Field Report: Tascam TH-2000 Headphones
- Battery Maintenance: Testing and Charging