i think i've found out why EAC would return a rather strange GAP layout sometimes.
it's only a 1 special case, but it happens time to time.
when uncertain you can use Subcode Analyzer to take look at subchannel by yourself.
and so you will see something like this:
Frame P Q-CONTROL Q-ADDRESS Q-TNO Q-INDEX Q-MIN Q-SEC Q-FRAME Q-ZERO Q-AMIN Q-ASEC Q-AFRAME Q-CRC16
76661 000000000000000000000000 0 1 07 01 01 57 62 00 17 04 10 232f
76662 000000000000000000000000 0 1 07 01 01 57 63 00 17 04 11 995f
76663 000000000000000000000000 0 1 08 00 00 01 74 00 17 04 12 5021
76664 ffffffffffffffffffffffff 0 1 08 00 00 01 73 00 17 04 13 27d4
76665 ffffffffffffffffffffffff 0 1 08 00 00 01 72 00 17 04 14 fd62
76666 ffffffffffffffffffffffff 0 1 08 00 00 01 71 00 17 04 15 0391
.....
76811 ffffffffffffffffffffffff 0 1 08 00 00 00 01 00 17 06 10 6d70
76812 ffffffffffffffffffffffff 0 1 08 00 00 00 00 00 17 06 11 d700
76813 ffffffffffffffffffffffff 0 1 08 01 00 00 00 00 17 06 12 a0b0
76814 000000000000000000000000 0 1 08 01 00 00 01 00 17 06 13 1ac0
76815 000000000000000000000000 0 1 08 01 00 00 02 00 17 06 14 84f5
76816 000000000000000000000000 0 1 08 01 00 00 03 00 17 06 15 3e85this is a PostGAP for Track 07 from some PSX CD:
(last sector for this track from TOC is 76812)
TNO increase; INDEX=0; MSF - resets and counts back
(since it's 74 this time, we can assume result will be a multiple of 75)
and afterwards: INDEX=1; MSF - reset again and count forward
Q=76813-76663=150=2 sec;
this is i think what EAC would do on a 'Detection method A'
'Detection method B' appears to be something less raw since it works on drive that
can't do a full subchannel read and will return correct gaps for 1Data+1Audio CDs
on the other drives it would return a rather random numbers but somewhere close to 2"
so maybe it's just some command for a drive to get pauses and is like outdated by now.
i don't know what 'C' is
P=76814-76664=150=2sec
P goes with a little offset from Q but most of the time yields the same result
but sometimes it would differ, like on older Mega CD games P usually is 186 when Q=150
i guess for this or some other reason it is not used in the most soft at all i think.
#1
01:74>>02:00
Mega CD
[G-6003] Quiz Scramble Special
[G-6010] Pro Yakyuu Super League CD
[T-49014] Cosmic Fantasy Stories
Saturn
[GS-9101] Fighting Vipers (V1.010)
Frame P Q-CONTROL Q-ADDRESS Q-TNO Q-INDEX Q-MIN Q-SEC Q-FRAME Q-ZERO Q-AMIN Q-ASEC Q-AFRAME Q-CRC16
55506 ffffffffffffffffffffffff 0 1 18 01 00 16 09 00 12 22 05 8f53
55507 ffffffffffffffffffffffff 0 1 18 01 00 16 10 00 12 22 06 1316
55508 ffffffffffffffffffffffff 0 1 18 01 00 16 11 00 12 22 07 a966
55509 ffffffffffffffffffffffff 0 2 00 00 00 00 00 00 00 00 08 a07d
55510 ffffffffffffffffffffffff 0 1 19 00 00 01 73 00 12 22 09 6bc2
55511 ffffffffffffffffffffffff 0 1 19 00 00 01 72 00 12 22 10 428b
55512 ffffffffffffffffffffffff 0 1 19 00 00 01 71 00 12 22 11 bc78so this is what happens:
ther's ADRESS=2 sector right on boundary, actually it shadows last frame before Pause
(how can you know it's not shadowing a part of a Pause? you can do calc on P.
compared to other tracks, it should increase if it would. it does not in this case)
but EAC counts it as 1st sector of Pause and thus GAP increase by 1 frame
why it is there i don't know, i think it belongs to Audio CD standard and should not be
on mixed mode at all. though it is. on Mega CD and Saturn - every 98th frame.
CDRWin can get GAPs correct in this case.
#2
Other
Mega CD
[T-44024] Capcom no Quiz: Tono-sama no Yabou
GAP 01->02=04:00
[T-49014] Cosmic Fantasy Stories
GAP 56->57=01:73
Saturn
[GS-9015] Panzer Dragoon (V1.001)
GAP 01->02=02:01; rest are 02:00
[GS-9050] Godzilla: Rettousinnkann (V1.000)
GAP 05->06=02:39; rest are 01:74
[GS-9097] Virtua Cop 2 (V1.004)
GAP 10->11=01:74; rest are 02:00
even though strange GAPs appear to be valid.
