Horizontal tearing
Also called: picture tearing, line tearing, sync tearing, horizontal sync loss
Horizontal tearing is the sideways shearing of bands of lines when analog sync fails. See what breaks in the signal and how to build it with STATIC DRIFT.
WHAT CAUSES IT
Horizontal tearing is the sideways displacement of groups of scanlines that happens when a display cannot keep its horizontal timing locked to the incoming signal. Every line starts with a horizontal sync pulse, about 4.7 microseconds wide and sitting below black level, which a sync separator detects by slicing the signal near the middle of the pulse. A phase-locked loop in the display, the horizontal oscillator, compares those pulses against its own free-running 15.734 kHz clock and nudges itself into step. When noise, tape damage, a weak broadcast, or a processor corrupts the pulses, the separator misses some and triggers falsely on others. The oscillator then coasts or is yanked to a new phase, and the lines drawn in the meantime start at the wrong horizontal position. Because the loop has some inertia, the error builds over several lines and recovers over several more, so you get a band that leans, then a snap back. Digital screen tearing from a graphics card is a different fault: it is a mismatch of whole frames, not of scanline timing.
WHAT IT LOOKS LIKE
Horizontal slices of the picture slide left or right against the lines above and below, producing a stair step or a sawtooth along vertical edges. Mild cases show a few lines bending near a bright area. Severe cases cut the picture into bands tens of lines tall, each offset by a different amount, and the black blanking edge on one side becomes visible as the lines shift. Often the band leans, with each line offset slightly more than the last before it snaps back, which gives a slanted shear. The disturbance moves between frames and is rarely in the same place twice, unlike a tape crease, which stays put.
WHERE YOU SEE IT
Weak or noisy over-the-air analog television, damaged or worn tapes, paused VCRs, bad cable connections, game consoles with unstable output, and security recorders. It is a staple of glitch art, music videos, horror trailers, and any title sequence that wants to say the signal is breaking. In editorial work it often appears at the start or end of a shot to mask a transition, as a sign that the picture has been interrupted rather than cut.
RECREATE IT
STATIC DRIFT
CONTROLS STATIC BREAK, DRIFT, STATIC CHAOS
STATIC BREAK drives the sideways displacement of line groups, and DRIFT controls how much each group lean builds before it snaps back. Keep STATIC CHAOS low at first so the tears feel like sync failures rather than random noise. Animate in bursts of a few frames and then hold a clean picture, since constant tearing reads as a broken file.
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HOW TO MAKE IT IN AFTER EFFECTS
1. Pre-compose the footage and apply STATIC DRIFT. 2. Start with STATIC CHAOS and DRIFT low, and raise STATIC BREAK until one or two bands of lines shift sideways. 3. Raise DRIFT until the bands lean instead of stepping, so the shear has the sawtooth shape of a loop recovering. 4. Add STATIC CHAOS in small amounts if you want the tears to land in unpredictable places. 5. Keyframe STATIC BREAK as a burst: a clean frame, then a sharp rise for three to eight frames, then a quick fall. 6. For a transition, place the burst across the cut so the new shot arrives while the old one is still tearing. 7. If the effect is a sustained signal failure, hold a moderate value and add a slow keyframe so the intensity breathes. 8. Check a frame-by-frame scrub; single-frame tears are the most convincing. 9. If you need a vertical roll as well, add DRIFT ROLL with a very low value in the same effect.
QUESTIONS
- What causes horizontal tearing in analog video?
- The display fails to lock to the horizontal sync pulses at the start of each line, usually because of noise, tape damage, or a weak signal. The horizontal oscillator drifts, and groups of lines start at the wrong position, which creates visible sideways shifts.
- Is horizontal tearing the same as screen tearing in games?
- No. Screen tearing in games comes from presenting two different frames in one refresh, so a single horizontal seam appears. Analog horizontal tearing changes the sideways position of lines because of sync timing, and it usually shifts many bands. The two are easy to confuse because both show a visible seam, but they come from unrelated causes.
- How is it different from time base error?
- Time base error is a small, continuous ripple of line timing that wobbles edges by a pixel or two. Horizontal tearing is a larger failure of sync lock in which whole groups of lines are displaced, often with a visible snap back.
- Can tearing be repaired in a capture?
- Not really. The displaced lines are recorded in their wrong positions. A line-aware restoration tool can realign some of them, but fixing it at the source, with a better signal or a time base corrector, is far more reliable. Prevention matters most here, since cleaning the tape, trying another deck, or using a capture device with a time base corrector avoids baking it in.