DMcCloy said:
...Why would the audio on the actual legal feed KLZK-HD3 be behind the 97.7 translator feed?
I too can confirm that both the HD2 and HD3 signals are roughly 30 seconds behind their analog counterparts.
Like DMcCloy, I'm flummoxed at how the HD signals can be BEHIND the analog translators they're supposedly feeding. The only explanation I can think of is that RAMAR is NOT using HD to feed their analog translators, despite what the online article suggests.
Kent has it partially correct- there is some delay in the HD, but it depends on which multicast signal one is talking about. An HD radio receiver is just like an audio player on your PC- it takes several seconds for the file to buffer before anything plays. Analog radios start playing the moment you turn them on (old tube-types excepted of course), but digital receivers have to fill the buffer first before they play anything. This was a serious design limitation because no one wants a radio that doesn't start playing the moment you turn it on. So Ibiquity's solution was to have the HD receiver START in analog, then once the digital buffer was full, it would then TRANSITION to the HD signal. In order for this solution to work, the analog signal needed to be delayed by several seconds- roughly the time it took for the digital buffer to fill, like 8 to 10 seconds or so. As Kent mentioned, some HD stations do a better job at synchronizing the "blending" on HD1 than others.
The delay in HD2 and HD3 varies by the encoding scheme and equipment used. When I setup KOHM's HD2 signal, the delay was almost a full minute: audio would feed the HD2 encoder and it would be almost 60 seconds before the sound was broadcast over HD2. HD3 was about the same. One downside I realized was that EAS alerts sent over HD2 & 3 would be delayed by another minute!
If RAMAR was indeed using the KLZK HD signal to feed their analog translators on 96.9 and 97.7, the analog audio should FOLLOW what is heard on HD2 and HD3. That is not the case. The audio on analog 96.9 and 97.7 are almost 30 seconds AHEAD of the audio on KLZK's HD2 and HD3. As Kent suggests, there are other ways to feed translators and I submit that might be the case here. Anyone else care to hazard an explanation?
As for the poor quality of KLZK's HD3, that's the result of slicing the total bandwidth for multicasting. I don't recall the actual numbers, but after full fidelity on HD1, and reasonable fidelity on HD2, whatever is left over is available to use for HD3. I know that in early generation encoders, the broadcaster could choose how to split the available bandwidth between HD2 & HD3. There's also HD4 available now, but there's not many bits left over for it to work with.
