Interlaced scanning is a video display technique that splits each frame into alternating lines, displaying them in two passes. Originally developed for analog TV broadcasts, interlaced video helped conserve bandwidth while maintaining smooth motion.
While progressive scanning is now the standard for modern digital screens, interlaced video is still used in broadcast TV signals, security cameras, and older video formats.
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How Interlaced Scanning Works
Interlaced scanning splits each frame into two fields:
- First field: Displays the odd-numbered lines.
- Second field: Fills in the even-numbered lines.
Since these fields are displayed in quick succession—typically at 50 or 60 fields per second, depending on the region—they are perceived as a full image. This approach effectively doubles the frame rate without increasing the bandwidth required for transmission.
For decades, interlaced video was the standard for television broadcasting, appearing in formats like 1080i (interlaced) as opposed to 1080p (progressive). While it served its purpose in reducing data transmission requirements, interlacing can introduce artifacts such as flickering and motion blur, particularly on modern progressive-scan displays.
Progressive Scan vs. Interlaced Scan: What’s the Difference?
Unlike interlaced scanning, progressive scan displays each video frame in full, providing smoother, clearer images with fewer artifacts.
- Smooth Image – Progressive scan delivers a clearer, more stable image, making it ideal for fast-motion content like sports and gaming. Interlaced video can introduce motion artifacts and tearing when displayed on progressive screens.
- Bandwidth Conservation – Interlaced scanning reduces the amount of data needed for video transmission, which was useful for analog broadcasts. Progressive scanning, however, requires more bandwidth but provides better overall quality.
- Flicker Resolution – Interlaced scan formats can suffer from flickering, especially on static images or detailed graphics, whereas progressive scan eliminates flicker and produces a more stable picture.
Why Interlaced Scanning Is Outdated
While interlaced scanning worked well for early broadcasts, it doesn’t hold up on modern screens. Interlaced video can introduce motion artifacts, making fast-moving objects look blurry or jagged. It can also cause combing effects, where horizontal lines appear misaligned due to alternating fields. These issues make interlaced video less than ideal for streaming and digital displays.
Deinterlacing techniques solve this by converting interlaced video into a progressive format, improving playback quality. By merging separate fields into full frames, deinterlacing reduces motion issues and makes video smoother and clearer on modern screens.
Where Is Interlaced Video Still Used?
While progressive scanning is now the standard, interlaced video is still found in:
- Broadcast TV – Some cable and satellite TV channels still use interlaced formats, particularly in 1080i resolution.
- Old video recordings – Many archival TV broadcasts, DVDs, and camcorder footage were originally recorded in interlaced formats.
- Security cameras – Some CCTV and surveillance systems still utilize interlaced scanning for bandwidth efficiency.
When working with interlaced sources, it’s important to use proper conversion or playback methods to avoid artifacts when displayed on progressive screens.
Optimizing Video with Resi
When streaming live events, video quality and stability are just as important as reducing bandwidth usage. While interlaced scanning was designed to conserve bandwidth in analog broadcasts, modern streaming relies on adaptive bitrate encoding and progressive scan formats for better efficiency and viewer experience.
Using Resi’s live streaming technology, interlaced video can be automatically converted to a progressive format for seamless playback. This process enhances video quality by eliminating motion artifacts while maintaining a stable image.
For organizations looking to transition from interlaced video sources to a modern streaming setup, Resi’s streaming solutions provide a reliable way to maintain video quality while reaching a wider audience.