Volume problems and poor advertising affect the listening experience
Recently, I was asked by a radio manager to evaluate his station’s stream and suggest improvements because listeners had been complaining about it.
Audience reactions affect ratings and revenue, so of course this situation had to be taken seriously.
A common complaint was about the station’s mobile app, which kept crashing and timing out after a certain amount of time, but since this was an issue with the app developer and not the engineers, I’ve put it aside for this discussion.
However, listeners also complained about advertisements. Their timing was not right. The advertisements started too late. Or they cut off the end of a song or other content.
The ads are triggered by metadata, so we checked the triggers (or “cue points”) to make sure they arrived correctly. We checked them at the output of the playback system, then at the pre-encoder, at the post-encoder (at the CDN), and at the player.
The encoder used by the broadcaster allowed for a delay in the metadata. By experimenting with the metadata delay settings in the broadcaster’s encoder, we were able to resolve the issue through trial and error.
In addition to triggering, metadata can also be used to achieve other functions. For example, information about the current track, station and album art are sent to the player. The beauty of metadata is that it is extensible – you define which data fields are sent and how many. Yes, as the creator you can define what the fields are and what they can do.
I strongly recommend that you “Streaming Audio Metadata Guide” published by the National Radio Systems Committee. I was involved in the project of putting this guide together. It provides a comprehensive toolbox to help you work with any stream. As well as explaining how to use metadata, it provides an incredible glossary of terms and issues surrounding streaming audio. It will be useful to any engineer working with streaming audio.
Another problem my client had was that the audio levels of the content and the audio levels of the inserted commercials did not match. This drives listeners crazy but can usually be solved with volume normalization.
For example, if the volume level for the inserted interstitial is set on the CDN (e.g. -18LKFS), make sure your produced content is at the same level. I suggest you refer to the AES standard AES77-2023: AES recommended loudness guidelines for Internet audio streaming and on-demand distribution.
With the adoption of this standard across the industry, streams from different broadcasters should reach comparable levels and listeners will no longer be shocked by a sudden increase of several decibels when they change sources or an interstitial is inserted.
Please note that the AES77 standard corresponds to what is AES-TD1008based on AES77. Some stream and podcast distributors refer to TD1008, so don’t be confused.
The volume is usually measured according to BS.1770 standard. It is measured in LKFS which stands for Loudness K-weighted Full Scale. LKFS is the equivalent of LUFS which stands for Loudness Units relative to Full Scale. This measurement is usually in decibels or dB. There are many loudness meters to measure the volume level.
The stream volume was normalized to -18 LKFS. Repairing the stream took a few days and everyone was happy in the end.
The resources above will help you with your own streaming efforts, but remember: the final judges are your eyes and ears—and those of your listeners.
(Check out more tech tips from Radio World)
