# Interlaced vs progressive video, and what 1080i vs 1080p means

> What is the difference between interlaced and progressive video? Learn why 1080i causes comb lines on Mac screens and how deinterlacing (Yadif) fixes it.

Published 2026-10-31 · Motion · https://www.hazenstudio.com/maclc/blog/interlaced-vs-progressive/

## In short

- Interlaced video captures half the picture scanlines at a time (odd then even lines), while progressive video captures every scanline simultaneously.
- Modern computer monitors and smartphone screens are natively progressive, which causes raw interlaced video to display jagged horizontal comb lines.
- Deinterlacing reconstructs full progressive frames using algorithms like Weave, Bob, or motion-adaptive Yadif to eliminate motion artifacts.
- 1080p is superior to 1080i for viewing, but older camcorders, DVD-Video discs, and broadcast TV streams frequently contain interlaced video.

Interlaced video splits each video frame into two alternating sets of horizontal scanlines (odd lines and even lines) captured a fraction of a second apart, while progressive video captures every scanline simultaneously across the entire sensor in a single instant. Progressive formats like 1080p deliver clean, razor-sharp motion on modern computer monitors, whereas interlaced formats like 1080i or DVD 480i produce jagged, comb-like horizontal stripes across moving objects unless properly deinterlaced.

While progressive capture has become the universal standard for streaming video, internet media, and cinema, decades of home camcorder tapes, DVD-Video collections, and digital television broadcasts remain encoded in interlaced formats. Understanding how interlacing operates—and how modern deinterlacing algorithms restore progressive clarity—ensures your older video archives look clean on modern Mac displays.

## What is the difference between interlaced (i) and progressive (p) video?

The letters "i" and "p" trailing a video resolution number describe how the image was captured by the camera and how it is transmitted across a video stream:

- **Progressive Video ("p", such as 1080p or 4K):** The camera sensor exposes all horizontal scanlines simultaneously. When displayed, the screen draws all 1,080 lines from top to bottom in a single sweep. Every pixel in the frame belongs to the exact same instant in time.
- **Interlaced Video ("i", such as 1080i or 480i):** The camera exposes only half the image at a time, creating two alternating **fields**:
  1. **Top Field (Odd Lines):** Scanlines 1, 3, 5, 7... up to line 1,079.
  2. **Bottom Field (Even Lines):** Scanlines 2, 4, 6, 8... up to line 1,080.

These two fields are captured sequentially: in a 60i broadcast, the odd field is captured at Time = 0.00 seconds, and the even field is captured at Time = 0.0167 seconds (1/60 of a second later). When combined, the two fields form one complete interlaced frame.

As standardized in television specifications like [Recommendation ITU-R BT.709](https://www.itu.int/rec/R-REC-BT.709), 1080i provided high spatial detail for broadcast networks while cutting transmission bandwidth in half.

## Why was interlaced video invented in the first place?

To understand why engineers invented interlacing, look back to the physics of early analog television in the 1930s.

Cathode-ray tube (CRT) televisions used a magnetic yoke to steer an electron beam across a phosphor-coated glass screen. The phosphors glowed brightly when struck by electrons, but decayed quickly into darkness. If an analog TV drew fewer than 50 or 60 frames per second, the phosphors dimmed noticeably between sweeps, creating a violent, headache-inducing whole-screen flicker.

Broadcasters faced an impossible engineering trade-off:
1. To eliminate flicker, they needed a refresh rate of at least 50 Hz or 60 Hz.
2. However, transmitting 50 or 60 full, progressive frames per second required massive radio frequency bandwidth that exceeded the capacity of national broadcast airwaves.

Engineers devised interlacing as a brilliant analog compression trick:
- By transmitting only half the picture lines (one field) every 1/50 or 1/60 of a second, the TV screen refreshed fast enough to trick the human eye into perceiving continuous, flicker-free illumination.
- At the same time, the signal consumed only half the radio bandwidth of a full progressive broadcast.

For CRT televisions—where the electron beam naturally drew alternating lines with slight optical phosphor persistence—interlacing worked exceptionally well.

## Why do interlaced videos look jagged with comb lines on a Mac?

The visual problem with interlaced video began when the world transitioned to digital flat panels: liquid crystal displays (LCDs), OLEDs, and modern Apple Retina screens.

Unlike analog CRTs that illuminate scanlines sequentially, modern computer monitors and MacBook displays are **natively progressive**. They hold all pixels active simultaneously and update the entire grid at once.

When an un-deinterlaced 1080i video file is displayed on a progressive Mac screen:
1. The video player draws the odd field (lines 1, 3, 5...) and the even field (lines 2, 4, 6...) together in the same window.
2. If the scene is completely static—such as a stationary landscape—the two fields align evenly into a crisp 1080p image.
3. However, if an actor walks past the camera, an athlete kicks a soccer ball, or the camera pans horizontally, the subject moved during the 1/60-second gap between field 1 and field 2.
4. Because odd lines show the actor where they were at Time 0, and even lines show the actor where they were at Time +16.7 ms, every moving boundary displays jagged horizontal teeth known as **combing artifacts** or "mice teeth."

On high-resolution Retina displays, combing artifacts look like harsh, distracting horizontal slats that destroy image sharpness.

## What is deinterlacing and how do weave, bob, and Yadif work?

To display an interlaced video cleanly on a progressive computer monitor, the media player must process the fields through a mathematical algorithm called **deinterlacing**.

Deinterlacing reconstructs a smooth, progressive image from alternating fields. The three primary methods vary dramatically in visual quality and computational complexity:

### 1. Weave Deinterlacing (No Processing)
Weave simply stitches adjacent odd and even fields together without any filtering.
- **Advantage:** Preserves 100 percent of the original vertical resolution on static backgrounds with zero CPU load.
- **Flaw:** Produces severe, unwatchable combing artifacts across any object in motion.

### 2. Bob Deinterlacing (Line Doubling)
Bob separates each field into an independent video frame and scales it vertically by 200 percent (interpolating the missing lines).
- **Advantage:** Completely eliminates combing artifacts and doubles temporal motion rate (converting 60i into smooth 60p).
- **Flaw:** Cuts vertical spatial resolution in half (reducing 1080i to 540 lines of real detail per frame), causing thin horizontal lines to shimmer and vibrate vertically in an annoying jitter.

### 3. Motion-Adaptive Deinterlacing (Yadif)
Modern video playback relies on motion-adaptive filtering, exemplified by the open-source **Yadif** (Yet Another DeInterlacing Filter) algorithm documented in [FFmpeg filter specifications](https://ffmpeg.org/ffmpeg-filters.html#yadif).

Yadif evaluates video on a pixel-by-pixel basis across spatial and temporal dimensions:
- If a pixel block is **stationary** (no movement between fields), Yadif applies weave filtering, preserving 100 percent of the original vertical detail and sharpness.
- If a pixel block is **in motion**, Yadif applies edge-directed spatial interpolation to fill in the missing scanlines without comb artifacts.

By combining the strengths of weave and bob, motion-adaptive deinterlacing renders crisp progressive video with sharp edges, stable static details, and zero comb lines.

MacLC, the free media player from Hazen Studio, includes built-in deinterlacing filters from VLC. When you open an interlaced 1080i broadcast recording, MPEG-TS stream, or unencrypted VOB file, MacLC can remove combing lines during playback without re-encoding: press D to turn deinterlacing on or off.

## 1080i vs 1080p: which format should you use?

| Specification | 1080i (Interlaced HD) | 1080p (Progressive Full HD) |
| :--- | :--- | :--- |
| **Active Scanlines per Instant** | 540 lines (half-frame field) | 1,080 lines (complete frame) |
| **Temporal Presentation** | 50 or 60 fields per second | 24, 30, or 60 full frames per second |
| **Transmission Bandwidth** | Low (engineered for 2000s TV broadcast) | Moderate to high |
| **Display Artifacts** | Combing lines unless deinterlaced | None; natively artifact-free |
| **Optimal Use Case** | Legacy cable television, broadcast archives | Digital cinema, Blu-ray, streaming media |
| **Modern Recommendation** | Avoid for new recordings; deinterlace old files | Standard high-definition choice |

According to technical studies by the [European Broadcasting Union (EBU Tech 3299)](https://tech.ebu.ch/publications/tech3299), progressive video formats consistently deliver superior perceived image quality and compression efficiency compared to interlaced formats, especially for fast sports action.

For an overview of how 1080p compares against modern ultra-high-definition displays, explore our guide on [1080p vs 4K video](/maclc/blog/1080p-vs-4k/).

## How to deinterlace video on a Mac without slow re-encoding

Many guides on the web advise users with interlaced camcorder tapes or broadcast recordings to download transcoding tools like HandBrake and re-encode their entire media library with a deinterlacing filter.

While re-encoding works, transcoding a two-hour 1080i video file on your Mac takes substantial time, consumes high CPU power, and inevitably introduces generational compression loss.

A much faster, non-destructive approach is using a modern video player that features real-time hardware-accelerated deinterlacing:
1. **Preserve Original Bit-for-Bit Files:** Keep your original master MPEG-2, DV, or AVCHD files intact without modifying their codecs.
2. **Real-Time Deinterlacing:** Modern players utilize Metal shaders and Apple Silicon's unified memory architecture to apply motion-adaptive Yadif deinterlacing on the fly at full 60 fps playback speed.
3. **Instant Playback:** Double-click your file and watch immediately with zero export delay.

If you are dealing with legacy physical media or camcorder archives, explore our guides on [how to play DVD VOB files on a Mac](/maclc/blog/how-to-play-dvd-vob-files-on-mac/) and [how to play TS and M2TS files on Mac](/maclc/blog/how-to-play-ts-m2ts-files-on-mac/). To understand how temporal presentation influences cinema, review our article explaining [what is frame rate](/maclc/blog/what-is-frame-rate/).

## Enjoying vintage and broadcast media on modern Retina screens

Interlaced video was one of the most brilliant engineering compromises of the 20th century, enabling flicker-free television broadcasts over limited radio bandwidth. But on the razor-sharp progressive Retina displays of modern Apple Silicon Macs, raw interlacing produces glaring combing artifacts.

By leveraging real-time motion-adaptive deinterlacing in media players like MacLC—or opting for progressive 1080p capture when creating new content—you get rid of comb lines and watch old footage, concert DVDs and TV recordings with clean motion.

## Questions people ask

### What is the difference between 1080i and 1080p?

Both formats have a resolution of 1920 × 1080 pixels. 1080p is progressive, capturing all 1,080 horizontal lines at once for a crisp, artifact-free image. 1080i is interlaced, sending 540 odd lines followed by 540 even lines 1/60 or 1/50 of a second later, which requires deinterlacing on computer screens.

### What causes horizontal 'comb lines' in old video files?

Comb lines (also known as combing or mice teeth) occur when interlaced video is displayed on a progressive monitor. Because the odd and even fields were captured at slightly different instants in time, moving objects have shifted position between fields, creating visible horizontal serrations.

### What is the best deinterlacing algorithm?

Yadif (Yet Another DeInterlacing Filter) is widely regarded as the best general-purpose deinterlacer. It is motion-adaptive: it preserves 100 percent vertical resolution in static parts of the image using weave filtering while intelligently interpolating only the pixels that moved.

### Do I need to re-encode my interlaced videos to play them on a Mac?

No. While tools like HandBrake can permanently deinterlace files, players like MacLC deinterlace in real time during playback, with no waiting and no re-encoding.

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MacLC is a free, open-source video player for Apple Silicon Macs: https://www.hazenstudio.com/maclc/ · download: https://www.hazenstudio.com/maclc/donate/