TagStation provides the album art and meta data to your playout system which in turn broadcasts the information over HD. Detailed below are a handful of factors that impact "how" and "when" a listener sees the information being broadcast.
Timely delivery of images over HD requires images to be broadcast ahead of audio events due to the limited bandwith available for HD transmission. Broadcasting images ahead of an audio event is possible with automation systems that support “next up” capability. If you are running a system that does not support “next up” capability, expect a delay between the start of the audio/text within the HD receiver, and the presence of the image.
Length of automation event
If an audio event is too short, the associated image is not likely to arrive for display before the next event begins. Delivering the image in this scenario would create an image "traffic jam" that results in a disparity between the audio broadcast and the visual displayed on the receiver.
TagStation accounts for these factors in accordance with the iBiquity spec and will not send images for automation events less than 27 seconds in length. In these cases, station logo will be delivered.
HD Reception factors
Transmission of artwork over HD Radio is dependent upon device reception. If HD reception drops out while the image is being transmitted, the data transferred is lost and the receiving device must wait until the image is rebroadcast before the image can be displayed.
Tune In factors
“When” a listener tunes to your HD signal also impacts whether or not they'll see an image displayed for a song.
If a listener tunes to your HD signal after the initial transmission of the image, they will not see an image until it is rebroadcast by your playout system. It’s also very possible that the listener may not ever see an image for the song.
Your playout system relies upon a piece of HD software developed by iBiquity called “JMSAC.” JMSAC enables your middleware to insert album art (received from TagStation) into your HD stream. It also controls how often the image is rebroadcast, based on these factors:
- The size of the image.
- The length of the song.
- The portion of the song’s duration for which an image can be rebroadcast (determined by the “Fraction of Song Duration Images Can Be Sent” setting in JMSAC).
- The number of HD channels set in JMSAC (determined by the “Duty Cycle For Number Of Repeat Calculation” setting in JMSAC).
- The bandwith available for the broadcasting of an image on the HD Importer (determined by the “Configuration Set” on the Importer).
With this in mind, here's the flow:
The image is transmitted at the time the song is broadcast (for automation systems that have “next up” capability).
If the listener tunes in after the initial image transmission, they must wait until the next transmission of the image – and that re-transmission is executed by JMSAC, based on the factors above.
At a certain point in the song, however, JMSAC's queueing of the image for re-transmission ceases - because it sees the end of the current song is near and begins the look ahead process to queue up the image for the next song. A user tuning in at this point of the process will not see an image for the current song.
Related Content: Troubleshooting image display issues on HD receivers