How To Avoid MPEG-2 Conversion "Motion Streaking"

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Level 2

418 points

How To Avoid MPEG-2 Conversion "Motion Streaking"

I've noticed a problem artifact I'm having when converting an existing QuickTime MPEG-2 clip to .mov, or .avi.

In the original MPEG-2 the motion, in say children playing hop scotch with eachother where their motion (or moving) legs, have a nice smooth transition in the motions.

However, when making a .mov conversion in QuickTime Pro, the motion in her "sweeping leg" now has horizontal lines in it. There isn't the "soft normal motion blur" of their legs, as in the original MPEG-2.

What is the "technical term" for this video artifact, and how can it be prevented, or what settings are best to use to avoid it.?

I would appreciate any input for either QuickTime conversions, or info on how to correct this ... possibly using Squeeze 4.1 (of which I also have installed on my Mac).

-David

800 mhz eMac/Superdrive, Mac OS X (10.2.x), LaCie External Hard Drive, 1 GB RAM

Posted on Aug 31, 2006 1:56 AM

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Answer 1

Aug 31, 2006 6:30 AM in response to DavidMac

The technical term for it is that it's an interlacing artifact. The source video is made up from fields, the odd lines of the image and the even lines of the image. The two fields are recorded at different times, with them being 1/60th second apart for NTSC and 1/50th second apart for PAL. That's enough time for a hop-scotching leg to have moved quite a distance.

Look in Squeeze for an option to deinterlace the video. That will take care of the problem, though it may make the image look slightly softer.

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Answer 2

DavidMac Author

Level 2

418 points

Aug 31, 2006 1:33 PM in response to Colin Holgate

"interlacing" .... that's what I thought it was.

However, using Sorenson Squeeze 4.1 does not solve the issue of
the interlacing from motion. The original MPEG-2 QuickTime has no
interlacing issues, the action is smooth and "artifact" clear.

It's just when I attempt to make a .mov or copy MPEG-2 (where I've slightly cropped the video using Sorenson Squeeze 4), that I always
get the interlacing in the copies.

In Squeeze 4 my settings are:

• CD Quicktime
• Remove Interlacing - Set to Auto
• Data Rate: 768+
• Frame Rate: 1:1
• Sorenson Video 3 Pro
• Sorenson 2 Pass VBR

and yet I still get the interlacing showing as small motion lines off someone's legs or arms in motion.

Any further suggestions?

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Answer 3

Aug 31, 2006 2:01 PM in response to DavidMac

Try something other than Auto. Auto would try to be clever about frames that don't have much movement in them, and would leave both fields in the final picture, but there may be cases where some movement still shows up.

Are you able to post an example output frame, just to make sure that it is a field related issue?

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Answer 4

Sep 2, 2006 1:11 AM in response to DavidMac

In the original MPEG-2 the motion, in say children playing hop scotch with eachother where their motion (or moving) legs, have a nice smooth transition in the motions.

So it sounds like the original clip is progressive.

What is the frame rate of the input vs the output you are using? How did you convert it to .mov or .avi -- with Squeeze, right?? Maybe it adjusted for the different input/output frame rates by blending different frames together in a single interlaced frame (the other field from another progressive frame)? I have purposefully done such things with JES Deinterlacer (I believe QT Player can't do that).

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