I did a little test and had WSJT-X offset my WAV file by 300ms.  This idea 
would allow custom correction of Dt values beyond just accurate time.  So audio 
delays could be allowed for.
I do believe this would be a very worthwhile addition to WSJT-X and may explain 
why people have been having problems decoding FT-4 (like me).
I was running PowerSDR and with all the buffer sizes and delays needed to 
prevent dropouts I was getting .6 and .7 Dt values.I've recently upgraded to 
Thetis where audio processing has improved so you see times here of around .3 
I found an example running FT4 just now where this picks up a decode for 
example since KK4HEG was 0.7 seconds off apparently.180000 -12  0.1  563 +  CQ 
EA6XQ JM19                       ? a1180000 -11 -0.0  900 +  YO7CVL KS4OT EM83  
                     180000  -1 -0.4 1941 +  CQ KK4HEG EM95                     
     Instead of the non-offset version180000 -12 -0.2  570 +  CQ EA6XQ JM19     
                  ? a1180000 -11 -0.3  900 +  YO7CVL KS4OT EM83                 
      


The original 2.1.0-rc5 wav file(base) (QT-5.9) 
C:\Users\mike\AppData\Local\WSJT-X\save >\WSJT\wsjtx\bin\jt9 --ft8 -d 3 
190506_170345.wav
170345  -1  0.3  208 ~  K0CYA KM4UJI R+06170345   0  0.3  330 ~  UA3PAB KA5HET 
EM25170345  -8  0.2  483 ~  K4WDY W5GOL EM25170345  -3  0.5  608 ~  N9XHN W2GC 
FM03170345  -8  0.3  784 ~  K3HW KB6PR DM14170345 -12  0.4  843 ~  VE2FZP W2RHS 
FM29170345   2  0.4 1064 ~  AA6DY W8HFJ -15170345  -6  0.6 1121 ~  K7OAC N3TRF 
FM09170345 -13  0.3 1512 ~  CQ CQ W3CCB FN01170345 -12  0.4 1554 ~  W9MDB WO3H 
-12170345   4  0.5 1611 ~  CQ AH6FF EM64170345 -12  0.4 1687 ~  UA3PAB W4MMP 
FM19170345 -20  0.7 1738 ~  CQ KA1AQP FN42                        a1170345  -2  
0.5 2006 ~  M0HAQ K0BLT DN81170345 -17  0.4 2176 ~  CQ SP9KR JO90170345 -10  
0.4 2232 ~  F4ECA KB1EFS -15170345 -13  0.3 2490 ~  CQ DX KK5ZV EL29170345  -7  
0.3  607 ~  IK4LZH N3XKB DM65<DecodeFinished>   0  18
With the 300ms offset done for the FT8 test with one line of code just before 
the wav file is written   
memmove((void*)data,(void*)&data[3600],sizeof(short)*samples-3600);  if 
(!wav.open (BWFFile::WriteOnly)


(base) (QT-5.9) C:\Users\mike\AppData\Local\WSJT-X\save >\WSJT\wsjtx\bin\jt9 
--ft8 -d 3 "..\..\WSJT-X - test\save\190506_170345.wav"170345  -1  0.1  208 ~  
K0CYA KM4UJI R+06170345   0 -0.0  330 ~  UA3PAB KA5HET EM25170345  -8 -0.1  483 
~  K4WDY W5GOL EM25170345  -3  0.2  608 ~  N9XHN W2GC FM03170345  -8 -0.0  784 
~  K3HW KB6PR DM14170345 -12  0.1  843 ~  VE2FZP W2RHS FM29170345   2  0.1 1064 
~  AA6DY W8HFJ -15170345  -6  0.3 1121 ~  K7OAC N3TRF FM09170345 -12 -0.0 1512 
~  CQ CQ W3CCB FN01170345 -12  0.1 1554 ~  W9MDB WO3H -12170345   5  0.2 1611 ~ 
 CQ AH6FF EM64170345 -12  0.1 1687 ~  UA3PAB W4MMP FM19170345 -20  0.4 1738 ~  
CQ KA1AQP FN42                        a1170345  -1  0.2 2006 ~  M0HAQ K0BLT 
DN81170345 -17  0.1 2176 ~  CQ SP9KR JO90170345 -10  0.1 2232 ~  F4ECA KB1EFS 
-15170345 -13  0.0 2490 ~  CQ DX KK5ZV EL29170345  -7  0.0  607 ~  IK4LZH N3XKB 
DM65<DecodeFinished>   0  18
  
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