The 2017 NAB exhibits open April 24, but the Broadcast Engineering and Information Technology Conference is happening the day before. Let’s preview Paul Shulins’ upcoming presentation on “The Effects of Bit Rate Reduction on Acoustical Watermarks for Ratings Systems.”
A short description of his presentation:
“Depending on market size, stations have the resources to employ the PPM, therefore tagging the market as a 'PPM market.’ PPM encoding is important for ratings measurements and it requires listeners to wear the meter on their belt. For the technology to work, PPM encoding is used. However, multiple factors are in play concerning the audio data bitrate and its effect on the PPM watermark. This paper will address the results of rigorous testing done using several stations in Boston.”
I spoke with Paul to learn more.
Doug Irwin: What are the multiple factors, and what are their effects on PPM?
Paul Shulins: On Sunday morning, I will be talking about the methods I used to test the effects of BRR on PPM. I will describe the reasons why I felt the need to run some tests, and will talk about the results, and some of them are surprising!
There are many variables that come into play when trying to ensure that watermarks get transmitted properly. The type of program material, the amplitude, frequency distribution and spectral content of the program material, along with a bit rate reduction, all these factors can all have a significant effect on the throughput of acoustical watermarks.
Irwin: Can you talk some about the testing procedures?
Shulins: The advent of the TVC-15 by 25/7 made this research practical. The TVC-15 is a new tool that is available for broadcasters that will accept any audio source, and allow you to evaluate it to extract the quality and efficiency of the PPM Watermarks. Using this tool, and running audio though various codecs, was an interesting experiment that produced some repeatable results that I will be sharing on Sunday.
I also compared linear off air audio to HD Radio audio at 64 kbps to see if there was any difference and graphed those results.
The session will for the first time explore some of the effects of BRR on watermarks, and encourage broadcasters to think about how much compression is acceptable, and whether it is worth risking possible PPM watermark transmission quality.
Sunday, April 23 is a day you should be in Las Vegas! Paul will deliver his presentation at LVCC, N256, at 9:30 a.m.