[pskmail] Re: Robust psk-modes on raspberry pi

  • From: Tarmo Huttunen <tarmopaha@xxxxxxxxx>
  • To: pskmail@xxxxxxxxxxxxx
  • Date: Tue, 5 Nov 2013 11:27:15 +0200

John, you really now what you are talking about!

Reason I started to think this is the fact that raspi indeed handels thor22
well, even with medium sink interpolator, but not psk-r modes at all. Or
lets say I have never get it decoding psk-r, not even slower ones.

You kind of confirmed my thoughts. I take this subject from back of my mind
to my table, start to look it closer when I have time. After all I havent
use raspi much after recent audio-related updates.

Thanks, Tarmo
On Nov 5, 2013 4:04 AM, "John Douyere" <vk2eta@xxxxxxxxx> wrote:

> Hello Tarmo,
>
> If you have correct decoding with PSK modes but not PSKR modes then the
> most likely reason is processing power.
>
> The processing load on the CPU is significantly higher due to the double
> Viterbi decoder and interleavers used for the PSKR decode.
>
> I have seen that issue on the earlier Android devices when I developed the
> andPskmail program.
>
> If you look at the rxpsk source code in the Android program (in Java) you
> will see that I spend time to work around these limitations. One solution I
> used quite effectively was to reduce the order of the filters to free-up
> some resources.
>
> From memory I reduce the order from 64 to 32, which means a slight out of
> band increase in interference but overall better than not having decode at
> all.
>
> But if you say that TXing is also not decodable, then I suspect that the
> CPU is simply not capable of processing that load.
>
> A good test would be to try the MFSK and THOR modes as well because the
> MFSK modes are very resource effective and the THOR modes the most CPU
> hungry.
>
> In my experience on the Android devices (from memory) here is the
> approximate hierarchy of CPU load by mode:
>
> PSK31
> ...
> PSK500
> MFSK16
> ...
> MFSK64
> PSK63F
> PSK125R
> ...
> PSK500R
> THOR8
> ...
> THOR22
>
> So have a look if the top of the list works but not the bottom. That
> should give you a good indication if the CPU is the issue or not.
>
> Also, have a look in Fldigi what interpolator you use. The linear one is
> the most CPU efficient.
>
> I also assume you have already selected the "Slow CPU" option in Fldigi.
>
> 73, John
>
>
>
> On Tue, Nov 5, 2013 at 12:03 PM, Tarmo Huttunen <tarmopaha@xxxxxxxxx>wrote:
>
>> Hello...
>>
>> I have wondered this oddity with raspberry-fldigi-jpskmail for a while:
>>
>> Psk-r modes are not working. Sympton is, after psk-r id is received,
>> raspberry does not decode anything. I mean, there will not come any
>> characters on fldigi window. Is that "normal" sympton related to slow cpu?
>>
>> In normal pc-setups if psk-r decoding fails, there will come at least
>> some nonsense text, am I right?
>>
>> I have started to wonder, if this psk-r problem is after all related to
>> prosessing power at all? Could this have something to do with varicode used
>> on psk-r modes? Missing symboltable or something similar?
>>
>> If I remember right, I also havent got pc to decode psk-r sent by
>> raspberry. (This was not what I was testing, just something I happend to
>> notice, and I am at work now, can not test again.)
>>
>> Do somebody have some advice for me, where should I look? Have somebody
>> used robust psk-modes on some other low-resource machine?
>>
>> Thanks
>> Tarmo, OH6ECF
>>
>
>

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