Hi Steve, That was a great explanation. Thank you. Have a happy and healthy
new year. 73, Sam W2JDB
-----Original Message-----
From: Steven Franke via wsjt-devel <wsjt-devel@lists.sourceforge.net>
To: WSJT software development <wsjt-devel@lists.sourceforge.net>
Cc: Steven Franke <s.j.fra...@icloud.com>
Sent: Thu, Dec 26, 2019 10:24 am
Subject: Re: [wsjt-devel] 3 passes??
Mike and Bill,
WSJT-X does three decoding passes, where a “pass” consists of the following
steps:
1. do spectral analysis and make a list of likely FT8 signal candidates, sorted
in order of increasing offset frequency. If a candidate is found near the
current Rx frequency, put that candidate at the top of the list.2. try to sync
each candidate and, if successful, attempt to decode multiple times using
different methods for symbol detection and using different amounts of a priori
(AP) info, depending on the current state of the QSO progress indicator3. for
each successful decode, subtract the signal from the audio waveform before
attempting to decode the next candidate on the list.
Your screenshot shows that your rx frequency was set to something near 1824 Hz
offset, and that successful decodes were obtained on the first two passes. No
decodes were obtained on the third pass in the example that you provided.
73 Steve k9an
On Dec 26, 2019, at 9:06 AM, Bill Somerville <g4...@classdesign.com> wrote:
Mike,
I don't see any evidence of a 4th decoding pass in the list of decodes you
provided in your OP. What makes you think there is such a pass?
I see a single decode at 1824 Hz which I assume is at or very near you
currently set Rx audio offset, I see 24 decodes in ascending frequency offset
followed by another 4 from the final pass, again in ascending frequency offset
order.
Decodes are processed sequentially, there is no "still being worked on". AP
decodes, if enabled, will be tried if the non-AP decoding attempts have failed
to produce a decode for a candidate, before moving on to the next candidate in
a decoding pass.
73
Bill
G4WJS.
On 26/12/2019 14:56, Black Michael via wsjt-devel wrote:
OK...let's call it 4-pass then....I wasn't including the rx offset as
pass#1.
I didn't think anything was happening after what you're calling the 3rd pass
occurs...but 3 more decodes show up. So that's the AP or some decodes are still
being worked on after the 3rd pass?
Mike
On Thursday, December 26, 2019, 08:50:50 AM CST, Bill Somerville
<g4...@classdesign.com> wrote:
On 26/12/2019 14:36, Black Michael via wsjt-devel wrote:
> Is there a 3-pass going on now in 2.1.2?
> I'm seeing 3 passes from the decodes.....
> de Mike W9MDB
Mike,
this is nothing new. The first decode attempt is at the Rx audio offset,
then another across the passband, and a third after subtracting
facsimiles of the decodes so far. There are also different decoding
strategies attempted on each candidate signal depending on the decoding
depth settings and whether AP decoding is enabled, at least until a
successful decode is achieved for each candidate.
73
Bill
G4WJS.
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