[App_rpt-users] Simulcast buffer value issue

[Tim Sawyer]

The DAC issue certainly won't cause audio to break up. It only affects
simulcast systems. But, there may be no DAC issue at all. Here's the
background.

When simulcasting the audio from all (non captured) transmitters needs to
arrive at the receiver with in an acceptable time frame (80 us). The DAC
theory was that it didn't start sending audio at correct clock cycle every
time. That would cause the audio to be out of sync between RTCMs causing
simulcast distortion.

As I said, that was the theory. The new theory is that the external clock
source was causing the DAC to trigger inappropriately. I spoke with someone
I met here on the list (Kevin I think its was) who is using a different
external clock and reports perfect simulcast operations.




On Mon, Feb 12, 2018 at 1:17 PM, Sam Nabkey <sam.nabkey at gmail.com> wrote:

> What is the DAC issue?  I've got horrible breakup issues on a node running
> three RTCM's not voting or simulcasting.
>
> The Hamvoip image does it much better.
>
> Too bad we all can't just get along..
>
> On Feb 12, 2018 15:04, "Tim Sawyer" <tisawyer at gmail.com> wrote:
>
>> That sounds different than the DAC issue. I've noticed variable audio
>> delay even on USB dongle nodes. My hunch is that it is some how related to
>> network latency, strange as that seems. The HamVoIP.org guys say they have
>> improved this to the point where there is consistently very little latency.
>> I once asked them if they thought their fix would apply to RTCMs but they
>> didn't know. As we know HamVoIP is not open source so us intel/AMD folks
>> don't get the improvements.
>>
>> On Thu, Feb 8, 2018 at 6:43 PM, Hayden Honeywood <haydenph91 at gmail.com>
>> wrote:
>>
>>> Hi guys,
>>> Been simulcasting for a little while now, has anyone come across the
>>> following issue, simulcasted or not.
>>>
>>> Sometimes it seems the audio echo back upon unkey seems to be
>>> excessively long. Usually I hear the last syllable, but sometimes at worst
>>> I'll be getting several words worth, probably 2 seconds.
>>>
>>> I had Simulcast launch delay set on one of my mains sites to 10
>>> microseconds and it seemed to happen a lot more often, however I have heard
>>> it happen even when this value is zero on all sites.
>>>
>>> I seem to recall Tim mentioned in a post somewhere that the timing in
>>> the PIC does not always launch at the same time. Is this the likely problem
>>> here? I can't refer that post as I think it was on the now defunct oncosec?
>>> mailing list.
>>>
>>> Internet connections are high quality stable connections with average
>>> ping times of 25-30ms. I haven't correlated it to a particular time of day
>>> yet.
>>>
>>> Regards
>>> Hayden VK7HH
>>>
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>>
>>
>>
>> --
>> Tim WD6AWP
>>
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-- 
Tim WD6AWP
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