Interlaced video is a technique developed for transmitting television signals using limited bandwidth.
In an interlaced system, only half the number of horizontal lines for each frame of video are transmitted at a time. This creates two fields that make up a single video frame:
- The upper field (odd-numbered lines) is drawn to the screen first from top to bottom
- The lower field (even-numbered lines) is drawn next from top to bottom
Due to the speed of transmission and persistence of vision, viewers perceive each frame in full resolution even though only half the lines are displayed at a time.
When and where interlaced video is used
Interlaced video was commonly used in:
- Analog television standards
- Some digital television standards
- Older video cameras and recording formats
It allowed higher perceived frame rates and resolution within the limited bandwidth constraints of early broadcast systems.
Advantages of interlaced video
- Reduced bandwidth requirements compared to progressive video
- Higher perceived motion resolution at lower frame rates
- Compatibility with legacy broadcast and display systems
Challenges with interlaced video
- Visible artifacts like flickering on thin horizontal lines
- Combing artifacts when motion occurs between fields
- Difficulty freezing frames or creating slow-motion
- Complexity in video editing and post-production workflows
Interlaced vs. progressive video
Modern digital video systems typically use progressive scanning, where all lines of each frame are captured and displayed sequentially. This avoids interlacing artifacts but requires more bandwidth.
When working with interlaced footage in Premiere Pro, you may need to:
- Set the correct field order for clips
- Apply deinterlacing effects for certain editing tasks
- Choose appropriate export settings for interlaced or progressive output
Understanding interlaced video helps ensure proper handling of legacy formats and optimal quality when working with or converting interlaced content in Premiere Pro.
