Interlaced and Progressive Scan

When you set up your encoder preset, and most likely when you set up your video capture equipment, you will need to know the difference between how interlaced and progressive scans affect your broadcast and which will be the best choice for your event. This is especially true in terms of video frame rate and pixel density. This article is intended to give you an overview of how progressive and interlaced scan types work and which will be the best choice for your event. If you would like more information about how to properly configure and convert your frame rate in the encoder preset, you can read over our recommended output formats.

What Is Interlaced Scan?

Interlaced scanning is a method for transmitting video signals by projecting half of the number of horizontal lines captured in each frame. By projecting the “half-frames” at a certain speed, the human eye perceives them as full-resolution images while allowing you to transmit only half of the amount of video data that you normally would. This means that you can effectively broadcast your content with a lower bandwidth than would normally be required.

Although it may be advantageous to utilize an interlaced scan for broadcasting across lower bandwidths, you may run into some video quality degradation, especially in terms of motion blur and lighting effects. This may be especially noticeable when projecting certain patterns such as checkered or striped clothing, buildings with segmented bricks or windows, etc. This is commonly referred to as “aliasing,” “combing,” or “moire.”

It should also be noted that broadcasting an interlaced video to most modern displays and monitors, which typically utilize progressive scan technology, which requires a process known as deinterlacing. As such, video quality can often depend on the device that is being used to transmit this information. In Studio, this often comes down to how your video is converted in your encoder preset.

What Is Progressive Scan?

A video rendered with progressive scanning creates a complete image with each frame. This means that images captured at a higher frame rate will be displayed with minimal to no motion distortion. Since most of the displays made within the past few decades utilize progressive scan technology, this also means that there is no need for other complex signal modifications, such as deinterlacing.

Interlaced video input must be deinterlaced prior to being sent to any web destinations, such as social media destinations or the embed code. This provides the best viewing experience for viewers on a variety of devices, such as desktop and mobile. 

An interlaced signal can be deinterlaced by selecting a progressive framerate in the “Output Format” section of the encoder preset. If you would like to learn more, you can look over our recommended output formats.

Which Scan Type Should I Use for My Broadcast?

When streaming to Web

To maintain the best level of quality from your video cameras through your video infrastructure to the Resi cloud (social media and stream URLs included), a progressive scan should be used without any frame rate conversions in your signal path or within your encoder preset.

When streaming to Multisite

To maintain the best level of quality from your video cameras through your video infrastructure to be used on decoders (or venues), the video signal should be maintained consistently through your video signal path, whether that be interlaced or progressive video. You can manually override the default to deinterlace on your encoder preset. 

When streaming to both Multisite and Web

To maintain the best level of quality from your video cameras through video infrastructure to be used on decoders and web destinations, a progressive scan should be used and maintained consistently through your video signal path, with no conversions on the encoder preset. If an interlaced video signal must be used, it should be maintained consistently through your video infrastructure, with no conversions on your encoder preset. An additional web preset can be used to deinterlace the video to be viewed as progressive on the Web. If this fits your use case, request a web preset from Resi Support.