how it works

A clock hidden in the hunger bar

Every Minecraft video carries a timestamp that nobody put there on purpose. joltcracker reads it, frame by frame, and checks whether the video's time and the game's time agree.

Why bother?

A cut in a speedrun or a challenge video is usually hunted down by eye: a flicker, a jump in the timer, an item that appears from nowhere. A careful edit leaves none of that. What it can't easily fix is the game's own clock, because nobody watching can see it.

Minecraft counts client ticks: twenty per second, from the moment the game launches, and it stops while a singleplayer game is paused. That number is never shown on screen. But it leaks into one thing you see all the time.

The wiggle

When your saturation runs out, the drumsticks of the hunger bar start to jolt. They look random, but every frame the game seeds its random generator with the tick counter (times 312871). On every tick that's a multiple of 3 × food + 1, each of the ten drumsticks moves one pixel up, one pixel down or stays put, straight from that generator.

That's 3¹⁰ = 59,049 possible patterns, and which one you see follows from the exact tick. So a jolt you can see is a reading of a clock you can't. The bar on the front page runs that same code.

Reading it off a video

1. Find the HUD. We grab a dozen frames across the video and work out where the hotbar is and how big the HUD is drawn (the GUI scale). Videos with a zoomed-in edit, a custom HUD or something covering the bar stop here, as "out of scope".
2. Read every frame. The video is split into one-minute pieces, read in parallel on our machines. In each frame we find the ten drumsticks, how full they are and how far each one sits from its resting place. A jolt lasts a frame or a few.
3. Turn jolts into ticks. Pattern + food level gives the ticks that could have drawn it. Often that's exactly one tick (a precise reading). When it's several, the neighbours decide: the clock runs at 20 ticks per second, so the right candidate is the one that lines up with the readings around it (inferred). What stays undecided is ambiguous and shown as a mark along the bottom of the graph.
4. Compare the clocks. For every reading we take the offset: the game's clock minus the video's own time. In an uncut, unpaused recording that difference never changes.

Reading the graph

• Flat line: one continuous stretch of play. The game clock and the video run together.
• Step down: the game clock stood still while the video kept going. A pause menu, a loading screen, a lag spike, an alt-tab on a paused game. Short ones are normal in every run.
• Jump up: the game clock kept running while the video skipped ahead. Gameplay is missing: a splice.
• Clock goes backwards: impossible within one game session. The game was closed and launched again, and the two recordings were joined: a restart, also a splice.

Hover a point for its tick and food level, and click it (or a marked change) to jump the video there and see it for yourself.

The verdicts

• clean one game session, with only short pauses.
• check by eye one game session, but the clock stopped for more than 10 seconds somewhere. Usually a pause or a long loading screen, but a pause can also hide an edit, so it's worth a look at that spot.
• spliced at least one jump up or a restart: the video isn't one continuous recording.
• no verdict the HUD was found but no clock reading came out (for example, saturation never ran out).
• out of scope we couldn't find a normal HUD to read.

What it can't tell you

• Whether the game was modded. A modded game has an honest clock too. Changed drop rates, a custom seed or a cheat client don't move it. joltcracker checks that a video is one continuous recording, nothing more.
• Anything while the bar is still. It only jolts with zero saturation, so stretches right after eating have no readings. A run that keeps eating golden carrots can have long gaps.
• Videos we can't read. Below 720p, resource packs that change the drumsticks, a facecam over the HUD, or a cropped or zoomed edit: the HUD has to look like vanilla Minecraft.
• Multiplayer and recording hiccups. A server game never pauses, so a step down there comes from lag or loading, not a menu. And a small jump up can be the recording software dropping frames rather than an edit: the size of the jump tells you how much is missing.

What we keep

We never store the video. Each minute is downloaded, read and deleted again. What we keep is what we read from it: the jolts, the clock readings and the verdict, so the next person to look up the same video gets the result right away.

Crack a video →