Deinterlacing is the process of converting interlaced video into progressive video so it displays cleanly on modern screens. If you’ve ever noticed horizontal lines or a comb-like pattern on moving objects in a video, you were likely looking at interlaced footage that hadn’t been properly deinterlaced. Understanding why this matters starts with how older video formats store their images.
How Interlaced Video Works
Most modern screens draw every line of an image from top to bottom in one pass. This is called progressive scanning, and it’s how your computer monitor, phone, and most TVs display content today.
Interlaced video works differently. Instead of drawing a complete image all at once, it splits each frame into two “fields.” The first field contains all the odd-numbered lines (1, 3, 5, 7…), and the second field contains all the even-numbered lines (2, 4, 6, 8…). These two fields are displayed one after the other in rapid alternation, and at high enough speeds your eye blends them into what looks like a single image. This technique dates back to early television broadcasting, where it allowed engineers to send a smooth-looking picture using half the bandwidth of a full frame.
The format 1080i, which is still the standard for most U.S. broadcast networks including those owned by Warner Bros. Discovery, Paramount Global, and Comcast, works exactly this way. Each 1080i frame is two separate fields captured at slightly different moments in time.
Why Interlaced Video Looks Wrong on Modern Screens
The problem shows up when you play interlaced video on a progressive display, which is essentially every screen made today. Because the two fields were captured at slightly different moments, anything that moved between those moments will be in a different position in each field. When both fields get combined into a single frame, moving objects develop a telltale “combing” artifact: horizontal lines that make edges look like the teeth of a comb. The faster the motion, the worse the combing gets.
This is the core reason deinterlacing exists. It reconstructs a clean, progressive image from those two interleaved fields so your screen can display it without visual glitches.
Common Deinterlacing Methods
Not all deinterlacing techniques produce the same results. The simplest approaches are fast but sacrifice quality, while more advanced methods take more processing power to deliver a cleaner image.
Weave
Weaving simply layers the two fields on top of each other to reconstruct a full frame. It’s the fastest method, but it’s also the least effective. Because it doesn’t account for motion between the two fields, combing artifacts often remain visible, especially in scenes with fast movement. Weaving works best on footage where the camera and subjects are mostly still.
Blend
Blending averages the two fields together rather than stacking them. This reduces combing, but the trade-off is a softer, slightly blurry image. You lose some sharpness because the averaging smooths out fine detail along with the artifacts.
Bob
Bob deinterlacing takes a different approach entirely. Instead of combining two fields into one frame, it displays each field as its own separate frame. Since each field only contains half the vertical lines of a full image, the missing lines need to be filled in. The simplest version just duplicates existing lines or averages neighboring pixels to create the missing ones. This doubles the frame rate, which can make motion look smoother, but it cuts vertical resolution. The result often has jagged edges and a flickering quality, particularly along diagonal lines where the interpolation doesn’t match the actual direction of the edge.
Adaptive and Motion-Compensated Methods
More sophisticated algorithms analyze each frame to detect which areas contain motion and which are static. Static areas can be safely woven together without combing, while moving areas get processed with interpolation or blending. The most advanced versions use motion compensation, which tracks how objects move between fields and uses that information to reconstruct cleaner frames. These methods produce the best results but require significantly more processing power.
Hardware vs. Software Deinterlacing
Deinterlacing can happen in two places: in your graphics hardware during playback, or in software during video editing or encoding. Hardware deinterlacing, handled by your GPU in real time, generally produces better results for playback than software-based encoding tools. Media players like VLC also offer real-time software deinterlacing filters that perform well.
For archiving or editing older footage, software tools give you more control over which algorithm to use and how aggressively to process the video. One important caveat: not all old video actually needs deinterlacing. Some content, particularly film transferred to video through a process called telecine, has a specific pattern of repeated fields rather than true interlacing. Applying standard deinterlacing to this footage can actually make it worse, creating duplicate and triplicate frames that bloat file sizes and degrade quality. The correct fix for telecined material is a different process called inverse telecine, which removes the extra fields to recover the original film frames.
When You’ll Encounter Deinterlacing
If you’re watching live TV through cable or an antenna, your television’s built-in processor is almost certainly deinterlacing 1080i signals in real time. You never see the interlaced fields because the TV handles the conversion before the image reaches the screen. Most modern TVs do this well enough that you’d never notice.
Where deinterlacing becomes something you actively deal with is in video editing and conversion. If you’re digitizing old VHS tapes, working with footage from older camcorders, or converting broadcast recordings for playback on a computer or phone, choosing the right deinterlacing method makes a real difference in the final quality. Most video editing software and conversion tools like Handbrake include deinterlacing options, typically letting you choose between a basic method (fast, lower quality) and an adaptive one (slower, cleaner results).
Streaming services and digital downloads are almost always progressive, so deinterlacing has already been done before the content reaches you. The main scenarios where you’ll need to think about it yourself are working with legacy video formats, capturing live broadcast signals, or editing footage that originated from interlaced sources.