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No streaming delay on HD subchannels

V

vw86

Since the advent of streaming radio I have always known there to be a delay between the OTA audio and the streaming audio. Depending on buffering and the streaming platform it usually ranges anywhere from 30-90 seconds.

I am in a loaner car for a few days with my first access to an HD radio in several years. After scanning the dial I was trying to find where some of these stations were streaming. I noticed the audio on the HD2/HD3 signals in the car were exactly in time with the streaming audio almost to the second. But if I flipped to the main HD1 channel, the customary minute-or-so delay was there.

Is there any particular reason for this? Is the audio feed for the HD2 signals coming from the same stream as available in the apps? All of the HD subchannels were iHeart O&O properties if that makes a difference.
 
vw86 said:
Is there any particular reason for this?
Click to expand...
No.

vw86 said:
Is the audio feed for the HD2 signals coming from the same stream as available in the apps?
Click to expand...
Couldn't be, because the HD encoding process takes several seconds. If the iHeart app was feeding the transmitter, the transmitter would be 10-12 seconds behind your phone.

This encoding delay affects all HD feeds, including the HD1.
 
vw86 said:
Since the advent of streaming radio I have always known there to be a delay between the OTA audio and the streaming audio. Depending on buffering and the streaming platform it usually ranges anywhere from 30-90 seconds.

I am in a loaner car for a few days with my first access to an HD radio in several years. After scanning the dial I was trying to find where some of these stations were streaming. I noticed the audio on the HD2/HD3 signals in the car were exactly in time with the streaming audio almost to the second. But if I flipped to the main HD1 channel, the customary minute-or-so delay was there.

Is there any particular reason for this? Is the audio feed for the HD2 signals coming from the same stream as available in the apps? All of the HD subchannels were iHeart O&O properties if that makes a difference.
Click to expand...
The playback analog signal is delayed slightly to match the encoding time of the digital. Therefore, when bouncing between analog and digital on a consumer radio in an area where the digital signal does not lock, the transition between the two types of signals should, it tuned correctly on the station's end, be aeamless.

With analog translators that "relay" a signal off an HD subchannel, it depends on how the transmitter of that particular translator receives the signal. Sometimes it's direct from the HD, sometimes it could be sent via a dedicated Internet stream or microwave.
 
vw86 said:
I am in a loaner car for a few days with my first access to an HD radio in several years. After scanning the dial I was trying to find where some of these stations were streaming. I noticed the audio on the HD2/HD3 signals in the car were exactly in time with the streaming audio almost to the second. But if I flipped to the main HD1 channel, the customary minute-or-so delay was there.

Is there any particular reason for this? Is the audio feed for the HD2 signals coming from the same stream as available in the apps? All of the HD subchannels were iHeart O&O properties if that makes a difference.
Click to expand...

If I were guessing, I would say the delay on the HD multicast signal was the same as the delay on their streams. Remember, your stream buffers and also has a slight delay. Not sure if that's something that can be done by design or if it just happened to be a fluke, but that would be my best guess.

Board-op is correct that the stream feeding the digital signal would result in an HD signal behind the stream. If a station is running HD, it's theoretically possible for your stream to catch up with (or even pass) the OTA audio depending on where the stream is encoded because both run on delays. The other direction, however, is not possible (or at least it isn't as far as I know).
 


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