Conventions
In this article I will use the following conventions:
[LIST=1]
[]light attack: jab punch or short kick;
[]impact freeze: period of time a character shakes right after being hit or blocking an attack;
[]hitstun: the time it takes to jump or attack after being hit;
[]blockstun: the time it takes to jump or attack after blocking an attack.
[/LIST]
Motivation
So there was a discussion a while ago in the Super Street Fighter II: Turbo HD Remix section about recovery or impact freeze being different somehow during combos or either as the first attack or a combination or isolated attacks. The issue is illustrated by the following fact:
*Factual CPS-2 SF2 information
Ryu can only combo a jab or crouching short into a hadouken if the light attack is the first hit of a combo.*
In other words, say you select Ryu and the round starts. you approach the enemy and do a crouching short canceled into a hadouken. If you were close enough, you will obtain a 2-hit combination: if the enemy did not block the kick, he will not be able to avoid getting hit by the projectile. On the other hand, would you perform a combination of an aerial attack then a crouching jab or short, then special-canceling it into a hadouken, the enemy would always be able to block or reverse the hadouken. It is impossible to obtain a 3-hit combination that way.
Tests
Maj has said that one could test it going frame by frame, which is what I have done. This test can be done with a 60 Hz camera and the actual game, or with an emulator, as suggested.
At first, I have tried it in Super Street Fighter II X: Grand Master Challenge, which is the Japanese version of Super Turbo. This had the same problem Super Turbo would present, which is that the game has all speeds with frame skipping, which makes the results inconsistent. In order to avoid the problem, I have tested it in Super Street Fighter II: The New Challengers (or S2, for short).
In S2, I have selected Ryu as player 2. I have done so by pressing forward kick, which yields a more pleasant color for the gi. As player 1, I have selected Ken. He has no such appropriate colors, so I have chosen the default one, with sad results. Ryu would be the attacking player, while Ken would be the dummy. The test would proceed as follows:[LIST]
[]I press an attack button for Ryu;
[]as the attack makes contact with the enemy, the score increases and I pause the game. This would be frame 0;
[*]I start counting frames and take notes of what happens in the screen.
[/LIST]
The first test consisted of Ryu hitting Ken with a cr.short, with no previous attacks. The data obtained was:
[LIST=1]
[]16th frame: dummy still locked
[]17th frame: dummy gets pushed back
[]18th frame: Ryu retracts his leg
[]22nd frame: Ryu recovers
[*]28th frame: dummy recovers.
[/LIST]
The second test consisted of Ryu hitting Ken with a crouching short kick after aerial roundhouse. The data was:
[LIST=1]
[]15th frame: dummy still locked
[]16th frame: dummy gets pushed back
[]18th frame: Ryu retracts his leg
[]22nd frame: Ryu recovers
[*]27th frame: dummy recovers.
[/LIST]
This shows that impact freeze and recovery do not change for the attacker. However, the character being hit is held locked in impact freeze one extra frame when the crouching short is the first attack of a combo. The remaining recovery does not change, but is delayed by one frame due to the referred fact.
The next test was Ryu hitting Ken with a crouching strong punch, with no previous attacks.
[LIST=1]
[]16th frame: dummy still locked
[]17th frame: dummy gets pushed back
[]18th frame: Ryu retracts his arm
[]21st frame: Ryu gets his arm close to his body
[]24th frame: Ryu recovers
[]33rd frame: dummy recovers
[/LIST]
The following test was Ryu hitting Ken with a crouching strong punch after aerial roundhouse.
[LIST=1]
[]15th frame: dummy still locked
[]16th frame: dummy gets pushed back
[]18th frame: Ryu retracts his arm
[]21st frame: Ryu gets his arm close to his body
[]24th frame: Ryu recovers
[]32nd frame: enemy recovers.
[/LIST]
This also presents constant impact freeze and recovery for the attacker and constant (delayed) recovery for the character being hit, with the impact freeze being one frame longer when the cr.strong is the first attack. Certainly, the same would happen for fierce or roundhouse, that is, the impact freeze does not depend on the attack itself, but it is longer by one frame for isolated attacks and the first ones in combos.
Finally, I have tested what happens on block. The following two tests are about a blocked crouching strong as a single attack or after a previous attack. In that case, I have used an aerial roundhouse, but any other attacks would give the same results. The difference is that blocked attacks do not increase the score, but it was easy enough to pause when Ryu extends his arm, which is the first active frame of his crouching strong punch.
Blocked crouching strong as a single attack:
[LIST=1]
[]16th frame: character still locked
[]17th frame: character gets pushed back
[]18th frame: Ryu retracts his arm
[]21st frame: Ryu gets his arm close to his body
[]24th frame: Ryu recovers
[]34th frame: enemy recovers.
[/LIST]
Blocked crouching strong right after blocked aerial roundhouse:
[LIST=1]
[]15th frame: character still locked
[]16th frame: character gets pushed back
[]18th frame: Ryu retracts his arm
[]21st frame: Ryu gets his arm close to his body
[]24th frame: Ryu recovers
[]33rd frame: enemy recovers.
[/LIST]
Similarly, the impact freeze is longer if the move is the first attack of a block string. However, the recovery time for blocked attacks is a frame longer with respect to attacks that are not blocked.
Conclusion
In S2, impact freeze is 16 frames for isolated attacks and 15 frames during combos and block strings. The recovery for jab or short is 12 frames after impact freeze ends, while the recovery for strong or forward is 17 frames after impact freeze. These recoveries are one frame longer for blocked attacks.
Extra info
The inconclusive results when testing with Japanese Super Turbo, which has frame skipping, were:
cr.strong
11 frame: character still locked
12 frame: character gets pushed back
14 frame: Ryu retracts his arm
16 frame: Ryu gets his arm close to his body
18-19 frame (varies): Ryu recovers
25-26 frame: enemy recovers
11 frame: character still locked
12 frame: character gets pushed back
14-15 frame: Ryu retracts his arm
16-17 frame: Ryu gets his arm close to his body
19 frame: Ryu recovers
24-26 frame: enemy recovers
cr.short
12 frame: character still locked
13 frame: character gets pushed back
14-15 frame: Ryu retracts his leg
17-18 frame: Ryu recovers
21-22 frame: enemy recovers
11-12 frame: character still locked
13 frame: character gets pushed back
14-15 frame: Ryu retracts his leg
17-18 frame: Ryu recovers
21-22 frame: enemy recovers
This is only what I could see and results would vary, due to frames not being shown.