in the official statistics list in MD there's a list of character's jumping speeds:
i copied it here because i'm too lazy to figure out how to link to the particular post.
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Jumping Speed - Jumping speed is how long it takes to do a jump from the ground. Every aerial jump (a.k.a. 2nd jump) takes 1 frame (starts instantaneously), as it's proven by the Screw Attack weapon, which hits anything nearby the EXACT INSTANT the character with the Screw Attack item jumps. Also, characters jump slower when they're big (Giant Melee and/or with a Super Mushroom) and they jump faster from the ground when they're small (Tiny Melee and/or with a Poison Mushroom)
Also please note that [for example] Fox (4 frames jumping speed) is in the AIR on frame 4+, so that means that the jumping ANIMATION (frames on the ground) is 3 frames for Fox.
---For more information on jumping speed go here:
http://www.smashboards.com/showthre...1183#post651183
4 frames - Fox / Ice Climbers / Kirby / Pichu / Pikachu / Samus / Sheik
5 frames - Captain Falcon / Dr. Mario / Luigi / Mario / Marth / Mr. Game & Watch / Ness / Young Link
6 frames - DK / Falco / Jigglypuff / Mewtwo / Peach / Roy / Yoshi
7 frames - Ganondorf / Link / Zelda
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9 frames - Bowser
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so according to this, Fox is technically in the air by frame 4. He's in the jumping =animation= for 3 frames.
also, according to the link in that post, you can't be holding the jump button on frame 3 if you want to short hop, which explains why it's so ****ing hard to learn how to sh with fox. =p
imagine if wavedashing required you to sh...oh man waveshining would be nigh impossible...