Hi Joe and all, 

This message summarizes my recent work on jt65 decoding in 1.6.1.

I’ve added 3 new entries to the table summarizing JT-65a decoding results on my 
batch of 333 20m .wav files. 

Program                   Good     Bad   Soft    Decoder
--------------------------------------------------------------------------------------------------------
1. WSJT-X r5922        3125      0     574    BM+kvasd (18.4% kvasd)
2. WSJT-X r5922        3123      2     572    BM+sfrsd (18.4% sfrsd, 
ntrials=10000)
3. WSJT-X r5922        2551      0     0         BM only
4. WSJT-X r5955        2704      0     482    BM+sfrsd2 (17.8% sfrsd, 
ntrials=5000)
5. WSJT-X r5955        2222      0               BM only
6. WSJT-X r5970'       2352             0        BM only (ntrials set equal to 
0, thresh0=2.5)
7. WSJT-X r5970        2930      ?     579    BM+sfrsd2 (19.7% sfrsd, 
thresh0=2.5, ntrials=2000)        
8. WSJT-X r5970’       3013      ?     ?        BM+sfrsd2 (thresh0=1.5, 
ntrials=2000)       

The r5970 version includes a number of tweaks:
 - threshold is now set to 2.5, ntrials is 2000
 - a couple of fixes for out-of-bounds errors related to the switch to the 
sync65 routing that I experienced on my data set
 - new erasure probabilities for use with the simple “sf” symbol metrics
 - simplification of the codeword acceptance criteria in sfrsd2 and extract - 
all acceptance tests moved into sfrsd2. 

I did many runs (my notes from this weekend include 25 runs with various tweaks 
and changes) and concluded that, for my data, I got better results using 
matched sf symbol metrics and erasure probabilities — ymmv. 

While performance is significantly better in r5970 than it was in r5955, the 
overall number of decodes is still less than what it was back in r5922. On the 
other hand r5970 is running much faster than r5922 did, because r5922 used 
ntrials=10000. 

Case 8 shows that we can obtain 83 more decodes by lowering the threshold to 
1.5, but execution time increases significantly because of the larger number of 
spurious syncs.

Also, comparison of cases 6 and 7 shows that the percentage of total decodes 
obtained using sfrsd2 is almost 20% in r5970, and is higher than previously 
seen with kvasd or sfrsd in r5922.

Steve k9an
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