ipDTL is an IP codec running in a web-browser and used for remote broadcasts, including television and radio. It is a replacement for classic ISDN audio codecs, with which it has Backward compatibility. It is also capable of video transmissions and can be used in the field with some mobile devices.
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History
ipDTL was developed by former BBC sound engineer Kevin Leach. Leach developed the technology using the open-source codec OPUS from the Google Chrome web browser. He was able to obtain higher audio quality than ISDN by accessing a website through Chrome. Audio quality of 72 kbit/s mono for voice contributors, 320 kbit/s for outside broadcasts with music, and 3 Mbit/s video at 1080p for video contributions on TV programs are possible. Leach launched the technology in 2013 as an initially free service for radio stations, but shifted to a subscription model shortly after.
Overview
ipDTL utilizes the webRTC and web audio technologies. It is designed primarily for Blink-based browsers like Google Chrome or Opera and runs on all platforms except iOS where these browsers are supported. The codecs used are Opus for audio and VP8 for video. The supported audio bandwidth is up to 320kbit/s (stereo), and up to 3Mbit/s for video (1080p).
Connections are DTLS-encrypted and established point-to-point. Where a point-to-point connection is not possible, TURN relay servers are used to route the audio. TURN servers in the US, UK and Japan are available, with an independent backup system being maintained at ipdtl2.com. Connections can also be made through a special URL that allows users to access another account and connect with it. ipDTL uses a proprietary signaling method but also supports SIP for interoperability with other devices and applications such as Comrex Access and Media5-fone, and can transcode between Opus, G.722 and G.711. This also allows for Interoperability with legacy ISDN hardware via cloud based bridging servers.