How Can I Correct a Stretched Video That Has Half of the Lines?

Table of Contents

Reading time: 3 min

amped replay tutorials

Dear Amped fellows, welcome to this week’s post of the “How do I do this?” series! Today we’ll show you how Amped Replay can deal with a not so common yet very annoying artifact: stretched videos due to field-based recording. If the last words mean nothing to you, don’t miss this opportunity to learn something new! Keep reading to learn how to correct a stretched video that has half of the lines.

If your video looks stretched, go to Amped Replay‘s Enhance tab and activate the Correct filter. The “Auto” mode will typically solve the issue, but if it doesn’t, try the “Stretched Video” mode.

Before jumping to the solution, let’s spend a few moments understanding the issue. Say you’ve got a video that looks like this:

Screenshot of Amped Replay software showing video metadata with resolution width 704 pixels and height 240 pixel highlighted.

It’s definitely strange, isn’t it? This is the result of field-based recording. If you’ve read last week’s post about deinterlacing, then you know that some CCTV systems store interlaced videos. Some DVRs, instead of deinterlacing the video by weaving odd and even fields together, or interpolating the missing lines, directly write down fields to the output video file, treating them as if they were entire frames. This is shown in the picture below:

Visual diagram showing deinterlacing process with separate video fields and omitted interpolation to reconstruct progressive frames from interlaced video footage.

The result is a video that has half the number of rows than the original, and therefore looks heavily stretched. However, if you have Amped Replay, this is not an issue: it takes just one click to fix it.

How to Correct a Stretched Video Using Amped Replay

Let’s move to the Enhance tab and activate the Correct filter. By default, the filter is in “Auto” mode: it will examine the video and, if field-based recording is detected, it will apply the line doubling algorithm, as shown in our example:

Screenshot of Amped Replay software showing the Enhance tab with automatic correction settings applied to surveillance footage.

When you generate the report, you’ll get an explanation of what the “Auto” processing did in your specific case:

Processing Information section displaying video correction settings with mode set to Auto (Line Doubled) for deinterlacing in forensic video analysis.

If you stumble in a case where the “Auto” mode does not work, you can manually set the filter to the “Stretched Video (Line Doubling)” mode and check the result.

Dropdown menu in Amped Replay  software showing correction option Stretched Video (Line Doubling) for processing interlaced footage.

Conclusion

That’s all for today! We hope this tutorial helped you understand how to correct a stretched video caused by field-based recording. You can also follow us on LinkedIn, YouTube and X: we’ll post a link to every new tutorial so you won’t miss any!

Table of Contents

Share on

Subscribe to our Blog

Subscribe to Blog via Email

Enter your email address to subscribe to this blog and receive notifications of new posts by email.

Subscribe to our Blog

Related posts