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Interlace artifacts in a VHS capture?

Engaged ,
Feb 23, 2024 Feb 23, 2024

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I'm using Premiere to compare captures from VHS tapes. A friend with a whole heap of capture equipment and software, has generated 40 captures of the opening spiel from a professional VHS tape (we assumed it would be a good place to start our investigation), using different capture techniques, so that we can judge which is the method that gives the best results when we capture our own tapes.

 

The captures have been layered and aligned so that I can immediately compare any two by turning the layer visibility on and off.  Two such captures are Video 9 and Video 11 .

 

But something came up straight away that I can't explain. I have uploaded 6 screen shots taken from Premiere.  See attachments.

 

Video 9a, of rolling credits, shows horizontal lines through the letters, whereas Video 11a does not. Such lines are not visible at other points of the captures.

 

I have posted about this on a VCR forum, where it was suggested that the lines are interlacing. I'm not convinced, so I'd like a second opinion.

 

1. Assuming everything was functioning properly, I would have thought that that particular film frame, Video 9a, coming out of Hollywood, would be top quality and have purely white letters; that there should be no interlacing in the letters when that frame was scanned, and then interlaced for transmission (or recording to tape).

2. Further, given that the resolution of VHS tapes has something like 200 lines vertically, how is it possible to capture, and later on view in Premiere, fine horizontal lines such as in Video 9a, lines that correspond to 576 PAL lines? The source is ~200P, but I can see lines at 576P – but only in the letters.

 

I want to try to understand why those horizontal lines are present.

Any suggestions most appreciated

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Community Expert ,
Feb 23, 2024 Feb 23, 2024

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I don't see any interlaced artifacts. VHS is what it is: low quality SD footage.

How was this footage captured?

Upload a short clip to test.

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Community Expert ,
Feb 23, 2024 Feb 23, 2024

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quote

I'm using Premiere to compare captures from VHS tapes. A friend with a whole heap of capture equipment and software, has generated 40 captures of the opening spiel from a professional VHS tape (we assumed it would be a good place to start our investigation), using different capture techniques, so that we can judge which is the method that gives the best results when we capture our own tapes.


By @Guy Burns

 

Make sure that Premiere Pro interprets the correct field order from the files. Premiere Pro is not very good at interpret the correct field order in captured files that has not been captured inside Premiere Pro. So, when you import a file from your friend that is let´s say upper field first Premiere Pro can interpret that file as either lower field first or progressive and the result you get is interlacing artifacts. This can be fixed, but you must know what field order the source footage has.

 

So the first step is to find out that by using MediaInfo (mediaarea.net) that finds that info more correct than Premiere Pro. Install the app and go to File > Open > File and import the file used in Video 9a.jpg. Then go to View > Tree and look for Scan order under the video section. 

 

- MediaInfo: Bottom Field First=Lower Fields First inside Premiere Pro

- MediaInfo: Top Field First=Upper Fields First inside Premiere Pro

- MediaInfo: Progressive=No Fields (Progressive scan) Premiere Pro

 

Now, import the file in Premiere Pro and right click on the file in the Proejct panel and go to Modify > Interpret Footage. Under Field Order, make sure that the settings there matches what you found in MediaInfo and click OK. While you are there, make sure the the Pixel Aspect Ratio is correct as well. (and the frame rate...)

 

Now, create a timeline that matches the clip by dragging the clip to the New Item icon down right in the Project panel and play back the clip. You can verify the settings in the timeline by going to Sequence > Sequence Settings.

 

When you discover that you friends clips are, let´s say Upper Field First, you can change all clips in one go so while it is tedious it gets better once you have found out the properties of the source clips.

 

Any mismatch should be avoided and yes, interlaced footage is a pain sometimes.

 

Did that solve anything?

 

Averdahl_0-1708707103069.png

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Community Expert ,
Feb 23, 2024 Feb 23, 2024

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- MediaInfo: Top Field First=Lower Fields First inside Premiere Pro

 


By @Averdahl

 

There are avi's that do have upper field.

You need to use the Field Options and reverse field dominance.

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Community Expert ,
Feb 23, 2024 Feb 23, 2024

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quote

- MediaInfo: Top Field First=Lower Fields First inside Premiere Pro

 


By @Averdahl

 

There are avi's that do have upper field.

You need to use the Field Options and reverse field dominance.


By @Ann Bens

 

That was a typo, its corrected now.

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Engaged ,
Feb 24, 2024 Feb 24, 2024

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Thanks for the suggestions, but I must apologise for posting this question. I'm still learning about VCR captures and made a big mistake. I was confusing horizontal resolution with vertical resolution. I thought the specs of the VCR player, meant there were ~200 horizontal lines, but Horizontal Resolution actual means what it says: there are ~200 vertical lines across the screen. These are upscaled during capture to 720 to meet the DVD standard of 720 x 576.

 

The vertical resolution (the number of horizontal lines) is 576, meaning that interlacing artifacts, born of moving letters, will be clearly shown. They would not be visible, of course, if the vertical resolution was only 200.

 

Anyway, below is my explanation of what the two captures show, both taken with professional level gear, an AJA unit, similar to this one, which is selling for more than $1000 second hand. The software used was AJA VTR Xchange, exporting to ProRes. My observations below are the result of several hours spent with a knowledgeable friend, comparing all 40 captures, taken with a variety of equipment and software.

 

  • All captures are progressive (720 x 576), but the source is PAL interlaced.
  • Video 9a shows a rolling credit. Because the letters are moving upwards, the letters, when originally scanned and interlaced, had interlacing artifacts – they have been stretched vertically. These artifacts are baked into the VHS tape.
  • Video 11a does not show this interlacing. It was captured using different version of the software, software that was able to succesfully remove the interlacing on the fly, during the capture. None of the other 39 captures were able to do that. A superb result, and to me, a surprising result. Those AJA people have gone to a lot of bother to achieve that.

 

Again, thanks for the suggestions. I've learned a lot in the last day or so about VHS captures.

 

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Engaged ,
Feb 25, 2024 Feb 25, 2024

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I was confused about "horizontal resolution", and now I'm confused about interlacing.

 

The attached file (from the same video as the stills above), clearly shows interlacing in QT7, VLC and Premiere.

However:

  1. When I import it into Premiere, it comes up as "P", not interlaced.
  2. In the timeline, the interlacing is clearly visible.
  3. If I select Field Options > Always deinterlace, the interlacing is still there.
  4. But if I render or export, the interlacing disappears.

 

QT7 Pro does not report interlacing for this file, and neither does Media Info (maybe they never do).

 

I'm wondering about two things:

  • How do you determine if a file is interlaced?
  • Maybe there's a bug with my CS6. If someone is interested and has the time: does this file report as "P" in a more recent Premiere?

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Community Expert ,
Feb 25, 2024 Feb 25, 2024

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File is progressive

If interlaced artifacts are present in a progressive file, then it's backed in.

AnnBens_0-1708864886948.png

Nothing you can do about that. Bad conversion.

Always deinterlaced won't do anything on a progressive file. It only works on a interlaced file ion a progressive timeline.

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Community Expert ,
Feb 25, 2024 Feb 25, 2024

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I have tons of old interlaced footage.

Used Topaz AI to convert to Prores in 720p and did a grand job.

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