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HDVoice In Support of Radio: Tieline At TAB 2010

Some would say that HDVoice is my major passion. I’m not sure that this is true, but I will admit that I grow increasingly dissatisfied with the quality of PSTN audio I encounter in the course of life.

I am especially aggravated by radio & TV stations that use the PSTN to pass production audio. It’s as if they simply don’t care about the technical quality of their broadcast. Why not just give every reporter an old Sony Walkman style cassette recorder? That would actually sound better than a phone call in many cases.

I accept that for call-in style radio shows the PSTN is still the primary means of connecting to the audience, and many people will use cell phones as a matter of convenience. Given these facts audio quality is going to be variable…never great…and often very bad indeed. However, for cases where there is a reporter the field, or passing audio between remote studios, there are much better options.

Last month a reader question prompted a short investigation of how you might leverage wideband (HDVoice) telephony in support of a podcast or online radio show.

This past week I was tasked with working a booth at the Texas Association of Broadcasters annual convention and exhibition in Austin. While at the show I stumbled upon Tieline Technology, a company that makes IP-based wideband audio connective gear for radio & TV stations.

The various products that this Australian company offer are centered around sending production quality audio over IP-based transport. Their products are compatible with legacy PSTN codecs like G.711 for obvious reasons, but support wideband in various forms including G.722.

The solution that they were demonstrating comes in two parts; the first of which is a hardware interface they call Bridge-IT.

Bridge-IT is an interface between the two realms of IP and audio. It’s essentially an embedded Linux system running a soft phone.

Of course, that analogy doesn’t hold up very long. Bridge-IT is a SIP end-point for someone who doesn’t care to know anything about SIP. It has an impressive set of capabilities:

  • Suitable for point-to-point and multi-point (multiple unicast) IP connections over a variety of connection transports, including WANs like the internet.
  • Linear audio with a suite of high quality broadcast algorithms as standard, plus optional LC-AAC, HE-AAC v.1 and HE-AAC v.2.
  • Tieline’s loss-tolerant MusicPLUS algorithm provides up to 22 kHz stereo audio quality with 20ms coding delay at bit rates as low as 96kbps – making it ideal for today’s IP and 3G networks.
  • Tieline Music can deliver up to 15 kHz FM quality mono audio at bit-rates as low as 24Kbps, with only 20 milliseconds encoding delay.
  • QoS Performance Engine automatically manages jitter buffering, forward error correction and packet repair.
  • Full hardware front panel interface including navigation, LCD display, PPM metering and dialing key pad.
  • Web GUI for programming codec functionality and RS232 data connections.
  • TieServer for automatic software upgrades, peer-to-peer dialing using STUN and automatic buddy list dialing.
  • Broadcast quality analog XLR inputs/outputs.
  • XLR digital AES/EBU input/output.
  • Simultaneous analog and digital AES/EBU audio outputs.

Tieline offers two proprietary codecs that they call “Music” and “MusicPLUS.” These sound interesting, and show that the company has an awareness of the need for wide-bandwidth (15 or 22 KHz) at modest bit-rates and with low-latency.

These proprietary codecs would only come into play when both ends of a connection are Tieline devices. When interop with other end-points is required Bridge-IT falls back to G.722, or can optionally support various flavors of AAC.

In speaking with a representative from the company I asked if they have any awareness of SPEEX or CELT. He showed considerable enthusiasm for  open source codecs in general. They had some knowledge of SPEEX, but not CELT.

I went on to ask about G.719. He was not aware of that new ITU standard codec, but expressed some interest and actually took notes! He seemed genuinely interested in interop with other systems.

The gentleman went on to explain that G.722 was fine for voice application, but that the extended frequency response of other codecs yielded superior intelligibility when conducting an interview in a noisy environment….like on the TAB exhibit floor!

Unlike the net-top/Freeswitch combination that I was pondering previously, Bridge-IT is a proper commercial product. It’s an appliance. And you know how I feel about appliances. Bridge-IT lists for $1395 USD.

The second part of their solution is an iPhone application called Report-IT Live. Report-IT is available in several versions; from a limited function free version to a full-featured version for $250.

The principle behind Report-IT is very simple, it’s a dedicated function soft phone that doesn’t need to be setup. Just install the app and enter the IP address of the Bridge-IT device one time. The app turns your iPhone into a field recorder and IP uplink.

Report-IT “calls” back to the studio over 3G or Wifi establishing a bidirectional audio link capable of production quality audio. That might just make the iPhone the most cost effective and commonplace, high-quality, real-time audio connection available to a broadcaster.

I’m told that NPR is making use of Bridge-IT and Report-IT to send reports back from the field. In fact, Report-IT can act an an offline audio recorder and the FTP the recording back to the studio once it is complete.

Rarely does my professional life in broadcasting cross paths with my personal interest in audio & VoIP. Bridge-IT and Report-IT exist at this nexus, and I find them both immensely interesting.

This Post Has 4 Comments

    The Tieline Report-IT application will be handicapped unless a pro level XLR microphone can be easily connected to the 3.5mm iPhone 4 mic input. I have found such a solution.

    All the audio links must be in place to have HD quality field audio. The key is a special adapter / cable to interface an XLR mic to the iPhone 4.

    8/26/2010 KV Connection said to George Jones: “We did some testing with the low impedance microphone and there is no noticeable difference when using a 10ft or 15 ft or 30ft cable. The audio comes through well in all cases.” Below is a link to the 15ft $26.50 custom cable you requested.

    DESCRIPTION: Custom iPhone 4 Y-Cable with a
    (A.) 3.5mm TRRS male right-angle plug to a
    (B.) 3.5mm TRS Male headphone jack with 3 inches of cable, to a second branch with 15ft of cable to
    (C.) XLR female microphone jack.
    This cable incorporates impedance matching circuitry specifically to match the Sennheiser MD46 350 ohm low impedance dynamic microphone (and similar low impedance mics) to the iPhone 4. Connector A: 3.5mm TRRS Male Connector B: 3.5mm TRS Female Connector C: XLR Female Cable Type: Premium Mogami Shielded Audio Cable Cable Length: 3 inches to connector-B and 15ft to connector-C.

    The key here was the “special impedance matching circuitry” to connect a low impedance mic to the higher (> 800 ohms) requirements for the iPhone 4.

    George Jones

    1. Not to my knowledge. As of last summer when I met them they only had iOS apps available. That may have changed. Worth contacting them to find out.

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