Progressive Scan VS. Interlaced Scan: What are the Differences?

The two main ways of displaying video are progressive scan and interlaced scan. The former is especially common today, with the ‘p’ in 1080p short for ‘progressive’ (and not ‘pixels’, like many believe).

It’s vital that you know the differences between these options so you can decide which screen type works for you. Want to learn more? Keep reading to discover the pros and cons of each format.

Sign up to our newsletter

What is progressive scan?

Progressive scanning draws every line of a video frame in sequence (i.e., from top to bottom). In the case of 1080p video, each frame has 1080 unique lines. Most high-definition televisions and all LCD screens use this format; HDTVs are even able to convert interlaced video to progressive.

This technology was first available for 240p televisions during the 1930s, and is now incredibly popular in the 21st century. This is mainly due to the format’s smoother motion. When watching nearly any modern video, your device will most likely use progressive scan to render the footage.

What are the advantages of progressive scan?

As a highly popular way of rendering video, progressive scanning has plenty of benefits. This is the case whether you are watching television, playing video games, or just browsing the internet.

The main advantages of progressive scan include:

1. Less noise and distortion

By showing the full frame all at once, progressive video offers generally better quality and a more accurate image. Interlaced video, in contrast, can sometimes appear blurry as it does not render every part of the frame at the same time.

2. Higher resolution

Along similar lines, progressive scans use higher bandwidth compared to interlaced scanning and can produce high-resolution images more easily. This means progressive displays usually have a far better range of resolution options.

3. Better, more accurate colors

As progressive scans show the full frame every time, they only display the colors of that specific image. The end result is a more vibrant picture, whereas interlaced scan technology struggles to render accurate human skin tones.

4. Smoother motion

Progressive video has no ‘lag’ from previous frames. This is especially important if you intend to watch a fast-paced film or play a game. In the case of the latter, smoother motion will improve your reaction times while playing.

What are the disadvantages of progressive scan?

While this format is impressive, there are still some limitations to keep in mind. You can only make an informed decision on which type of display to use with a full idea of the drawbacks.

Here are the disadvantages of progressive scan:

1. More prone to image tearing

If you watch a video with a different refresh rate to your progressive scan display, this might lead to screen tearing. This is when the image retains information from previous frames, distorting the picture.

2. Requires more bandwidth

This format’s bandwidth requirements are what give you a high-quality image, with each frame taking up more data. However, this can slow the video (as well as your device) down while also using more space.

3. Higher processing intensity

In addition to high bandwidth, progressive scan also requires stronger technology with far better processing power. Videos with high resolutions or high frame rates (such as a 4K video at 60 frames per second) take this further.

4. Compatibility with other technology

Progressive scanning is very common and forms part of most displays, but older devices might not support this functionality. Analog cables and even some wireless networks often struggle to transmit these images without interference.

What is interlaced scan?

Interlaced scanning splits each frame into two fields, alternating between them with each line on the screen. This technology displays the odd-numbered lines first, followed by the even lines, to effectively double the video’s frame rate. With this, interlaced video creates a new half-frame 50 times each second.

An interlaced approach uses half the bandwidth and is thus a lot more efficient. These displays were once the best way to prevent flickering video, but are less common today. However, this is still a better choice than progressive scanning in certain situations. Ultimately, you must choose the technology that works for you.

Get to know more about DCATPoE

Get to know more about DVP500x-4U

What are the advantages of interlaced scan?

Most displays use progressive scanning, but interlaced video still has its uses that may make it the best choice for you. For example, most CRT and some plasma displays use interlaced video.

The advantages of interlaced scanning include:

1. Cost-effective

As these displays were once highly commonplace, the hardware is a lot cheaper and far more readily accessible. Broadcasting these signals is also usually easier in terms of cost, as they run along more channels on the available spectrum.

2. More resistant to image tearing

The alternating fields of interlaced video have less time between each frame, making them far less prone to screen tearing. There may still be inconsistencies between images, but the higher frame rate makes this less noticeable.

3. Less flickering

Similarly, interlaced displays are less likely to have issues with flickering due to the rapid refresh rate. This means that the frames blend together near-seamlessly, which is necessary to ensure a more comfortable experience when watching videos.

4. Low bandwidth use

Another key advantage of interlaced scan is its efficiency. Every frame only displays half-new information with each pass, it uses half the data while generating a smooth, high frame rate video. This approach was instrumental for older broadcast systems.

What are the disadvantages of interlaced scan?

With progressive scan mainly replacing interlaced video, there are notable downsides to this approach. It is up to you to decide if the low bandwidth and cost makes up for these issues.

Here are the disadvantages of interlaced scanning:

1. Produces lower quality video

The individual images of interlaced scanning offer lower quality when compared to progressive technology. This is most obvious when watching fast-motion video or playing video games; even with less screen tearing, there might be visual artifacts.

2. Not suitable for live video

An interlaced approach is less useful for live video, especially as it is not wholly compatible with many modern broadcast systems. Live broadcasts that make use of interlaced displays typically use deinterlacing to remove visual artifacts.

3. Visible scan lines

If you are close to an interlaced screen or pause the video, you might see the ‘scan lines’. These are afterimages of previous frames, which make the experience less seamless and are typically more noticeable on high-contrast monitors.

4. Limited resolution

The alternating fields of an interlaced display result in a lower vertical resolution. For example, a 1080i video signal has 540 lines in each field. However, combining them often leads to a loss of quality and sharpness.

Image scanning over the years: methods, changes

Before progressive and interlaced displays, televisions used ‘mechanical scanning’ with the aid of a rotating disk. From the 1920s onwards, the reduced flickering of interlaced displays allowed them to quickly become popular. CRT televisions using interlaced scanning soon dominated the market, in part due to their relatively low technical demands.

Analog broadcast systems throughout the 20th century mainly made use of interlaced video. As these technologies grew in efficiency, progressive scanning slowly became more practical and affordable. This approach was niche until the late 1970s, when the growth of home computing made progressive video essential due to the higher image quality.

Full HD television developed throughout the following decades, with displays typically favoring a progressive approach. LCD and LED screens grew in popularity, and mainly relied on progressive scans in contrast to CRT televisions. Today, though HD channels often broadcast an interlaced signal (usually 1080i), televisions generally convert this to progressive.

Progressive scan vs. interlaced scan: What are the differences?

Sign up to our newsletter

Progressive scan vs. interlaced scan: which is better, how to choose?

Progressive and interlaced scan displays each perform better in different situations, so you must carefully pick which one is best for you. For example, if your setup has limited bandwidth and needs to show several screens at once, an interlaced approach might be smoother.

However, if you want a high-quality image and can meet the requirements, you might fare better with a progressive monitor. An office setting or one where the quality may be less important can also save on money and bandwidth by selecting an interlaced display.