Distorted audio when both timeslots are in use?

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Joined: Sun Jan 12, 2020 4:27 am

Distorted audio when both timeslots are in use?

Post by kt4lh » Mon Jul 13, 2020 4:37 pm

Today I've noticed that when there are two continuous conversations going on the same repeater, one on TS1, one on TS2, occasionally the GD77 will start making a pretty terrible fluttering sound. If I flip to another repeater and right back, it's fine again.

At first I though it was because I did not have timeslot filtering on (it was in fact off the first time I heard this) but I switched that on and it happened several more times.

I'm not sure if this is a timing thing, like someone starts talking on both timeslots at once or what. I'm trying to figure out some kind of pattern to the issue but right now I haven't heard it again for a bit. I wonder if it's possible that me turning TS filtering back on and then changing the channel 'fixed' it for now. I'll experiment some more.

Anyone else noticed this before?

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Re: Distorted audio when both timeslots are in use?

Post by VK3KYY » Tue Jul 14, 2020 11:17 am

I've notices snatches of the other TS coming through, but not noticed garbling specifically happening more if both TS's are in use.

On the whole I get less garbling with the OpenGD77 than I used to with official firmware.
With the official firmware, I'd often have to change channels to get rid of garbling, but it now only seems to happen occasionally when someone is doing the new broadcast which is 30 minutes of continuous transmission.

I don't know how the official firmware handles the TS selection, but I think its different from the way this firmware does it.

Possibly if having both TS in use leads to an increase chance of garbling, is probably because we are loading the CPU too much, and it can't always handle the extra things we are asking it to do. e.g. the abilities to not filter by CC or TS come at a cost in terms of CPU usage, even if the filters are enabled, the code still has to perform some extra processing on every DMR frame etc.

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