Video editing terms explained – Part 2: Progressive (p) vs Interlaced (i) recordings

August 31, 2012 | By Simon Monahan

HD video is commonly presented in 720 or 1080 sizes, with a ‘p’ or’ i’ after the number, which is a shorthand for either ‘progressive’ or’ interlaced’. But what exactly do these two terms mean? In this second article in a series, which attempts to break down the technical aspects of video recording and editing, I explain how a displayed picture is composed.

When watching a video on screen the picture will be transmitted in one of two ways. The first method, used by computers and some media players, is to output full-frame images, displaying whole frames as single images, one after the other. This is called progressive (p) video. The second method, used by TV broadcasters, is to use interlaced images (i), that are made by blending elements from two adjacent frames one after the other, splicing odd and even lines together to form each frame. When a TV processes interlaced video it separates the lines from the adjacent frames and blends them together in the correct sequence to display the progressive video you’re used to watching. This process is called deinterlacing.

Progressive video contains more data than interlaced video and as a result images displayed appear sharper and more detailed, with no motion artefacts visible when watching sport or other quick motion sequences. The downside however is that because progressive video requires more data to be transmitted it is not a great choice for broadcasters, that instead choose to put out interlaced video, or owners of video cameras with limited storage capabilities. Modern cameras offer the ability to record both ‘p’ and ‘i’ video, with most editing software supporting both formats too. If you have plenty of storage space on your camera and want to record the best quality HD video possible choose progressive, otherwise opt for interlaced.

Frame rate

The last descriptor in this technical shorthand is a number sometimes seen at the end of a video description , e.g. 1080p/24 or 1080i/50. This last number after the slash denotes the speed of the video or TV, measured in frames per second, fps, or Hz (cycles per second). The greater the frame rate, the greater the quality of video displayed. Common video standards are 24Hz for movies and 50 or 60 for TV broadcasts and gaming. Interlaced video sources at 50 or 60Hz are usually deinterlaced and displayed by an HD TV at 25 or 30 progressive video frames per second.

If you have a question about this post, or would like to know more about a particular aspect of video recording & editing, let me know and I’ll try my best to answer it over the coming weeks.

Read the first post in the series, which explains the differences between standard and high definition video.

tom hartnett

I enjoy these posts and have a request for one. Can you demonstrate keyframe modes and how they are applied? I’m speaking of Absolute, Proportional,Relative to Start, Relative to End, Proportional (excl.
transitions), Relative to Start (excl.
transitions),Relative to End (excl.
transitions).

I know that short explanations follow each term in the help section, but what’s given on the page is not very meaningful to me. A demonstration should make things clear and may help my workflow.

thanks,
tomH

http://www.serif.com/ Mark Mauloni

Hi Tom,
I’m glad you enjoy our articles. Thanks for your great suggestion! I’m sure we can create an article that demonstrates keyframes in more depth. Stay tuned!

Michael Beaumont

If one records a video on a Sony DSC-HX20V using 1080i/50, after transferring to my PC, can this then be imported for film making, editing etc on MoviePlus X6 or must it be video’d in 1080p/24?
Mike B

SerifSimon

Hi Michael. MoviePlus X6 does support 1080i/50 & 60 video so you should have no problem editing and exporting this format. I wouldn’t generally recommend trying to export interlaced video as progressive video as the process of de-interlacing doesn’t always achieve perfect results.

Paul Bartlett

My camcorder can record in 1080p/50 but I don’t use it because I cannot edit & export to disc in MovieMakerx6. If I purchased a blu-ray writer and exported 1080p/50 edited footage to a blu-ray disc, would the quality be any better than the 1080i (AVCHD) that I export to a DVD disc, given that blu-ray is 1080p/24?

SerifSimon

Thanks for your
question, Paul. MoviePlus X6 does support
1080p/50 & 60 export but it is a limitation of media that these settings
can only be burned to Blu-ray Discs, not CDs.

1080p/50 & 60 will achieve
a superior picture quality than 1080i AVCHD. For the reasons discussed in the
article, progressive recordings are generally superior to interlaced
recordings. Another factor is that AVCHD
video is constrained to 18Mbps whereas Blu-ray supports up to 40Mbps.

It is worth noting that
not all Blu-ray players support 1080p/50 & 60 video. I think that most modern players do though. Regardless,
1080p/24 should still give a better picture quality than 1080i AVCHD.

MoviePlus does not have
a pre-set for 1080p/50 & 60. The way
to achieve this setting is to select Export Movie>File>MPEG video, choose
a Blu-ray pre-set and customise it to the settings you require.

Slmslm0

Thanks for this. I didn’t know the difference.
I thought television was 24 frames per second and DV was just under 30?

SerifSimon

Glad you’ve found this article helpful. Video is recorded and exported at many different settings and is dependent on a host of factors like where in the world you live, device captured on, storage, and how you want to view the end result.

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