An IBOC roadblock
Jun 1, 2003 12:00 PM, by Chriss Scherer, editor
In the middle of May, the road to IBOC took a major detour. What has been an ongoing work in progress with a predictable slow and steady pace has been stopped in its tracks. On May 15, the Digital Audio Broadcasting (DAB) subcommittee of the National Radio Systems Committee (NRSC) released a notice to its members stating that it is temporarily suspending its standards-setting process. Ibiquity Digital, the developer of in-band on-channel digital radio, continues working on a final system, but the NRSC has basically said, no more; call us when it's ready.
The key points of the NRSC memo state that:
�As a result of growing concerns over the audio quality of Ibiquity's low bit-rate codec, the NRSC DAB subcommittee is temporarily suspending its IBOC DAB standards-setting process.
�These concerns have arisen recently, as a result of both information submitted to the NRSC by Ibiquity as well as by demonstrations of the Ibiquity AM IBOC system at the 2003 CES, at NAB2003, and at the studios of National Public Radio (NPR) in Washington, D.C. � [At the NPR demo] Ibiquity stated the audio being demonstrated was based on the latest version of Ibiquity's proprietary audio coding algorithm, PAC, and was the version to be implemented in first-generation IBOC receivers.�
The DAB subcommittee members attending the NPR demonstration listened to the 36kb/s demonstration and felt that it was not suitable for broadcast. I'm not surprised. The low bit-rate demonstrations I have heard have obvious coding artifacts. I was always told that this was in development and that the next version would sound better.
We've been told that the next version will sound better for some time. When the so-called final version is being demonstrated and it does not provide an improvement in audio quality, or at least an equal level of audio quality, there is a problem.
As a review, the goals of the NRSC DAB subcommittee were set in 1998. Following the recent action, one major point in the group's stated goals stands out. The subcommittee is to study IBOC DAB systems and determine if they provide broadcasters and users with a digital signal with significantly greater quality and durability than available from the AM and FM analog systems that presently exist in the United States.
I'm pleased that the NRSC subcommittee has taken this action and not allowed the system to continue on its way to becoming a standard until appropriate improvements have been made.
Following the NRSC announcement, Ibiquity issued its own statement, agreeing with the assessment, but also pointing out that the NRSC has taken exception to the audio coding only and not the system architecture.
In demonstrations held as recently as one year ago, Ibiquity was using the AAC encoding algorithm and not PAC. The systems evaluated by the NRSC for its first AM and FM reports were based on AAC. All along Ibiquity has maintained that switching to PAC would be no problem. This obviously is not the case.
The AAC/PAC debate goes back to the USA Digital Radio and Lucent Digital Radio days before the two developers merged to form Ibiquity. PAC is a Lucent product, AAC is not.
One advantage to PAC is that it has the ability to be used in data slices to provide additional flexibility in its operation, particularly with changes in reception. In addition, by using PAC and not AAC, Ibiquity controls the coding and avoids paying a licensing fee to use someone else. Not that PAC is bad; it can sound good. The competition for the ultimate low bit-rate encoder is still going strong.
Some believe that IBOC will be another dark chapter in the radio history book, like AM stereo, RBDS, Amax and quad FM. The preface to the closing IBOC chapter may have been written. We'll see if the complete text follows.
What are your thoughts on IBOC? Is it a viable system or just a pipe dream? Tell us what you think.
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