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

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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:

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:

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.

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

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

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.

That’s all for today! We hope you’ve found this issue of the “Amped Replay Tutorials: How do I do this?” series interesting and useful! Stay tuned and don’t miss the next ones. You can also follow us on LinkedIn, YouTube, Twitter, and Facebook: we’ll post a link to every new tutorial so you won’t miss any!

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