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DVD 16x9 strobing issue on moving shots

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Chris Blair
DVD 16x9 strobing issue on moving shots
on Mar 16, 2009 at 6:37:15 pm

I posted this in the DVD authoring forum too.

We do a lot of compression and a fair amount of DVD encoding and authoring. We've encountered an annoying issue on our last couple of 16x9 projects that we've never seen before.

The DVD authored projects exhibit weird alaiasing on wide panoramic shots during diagonal moves (especially shots with lots of detail). This only occurs when played from a hardware DVD player and ONLY occurs on the extreme wide shots with diagonal movement. The moves are very slow and adhere to motion picture film panning rules for focal length, panning speed etc.

The aliasing isn't visible on camera moves on medium shots or closeups, or at least it's not objectionable. This only affects about 5 or 6 shots (our of hundreds) in either video.

Both projects used a variety of footage, from HD material shot on an HVX-200, to SD material shot on an SDX-900. All was shot widescreen and in 24P mode, then captured via SDI at 720x486 and edited 16x9. The videos look great playing back from the timeline on any monitor (even crappy ones) via component, SDI, S-video, composite, etc., and look great once output via SDI to DVCPro50 tape.

The ONLY difference in our workflow is we previously used Sonic ReelDVD software for DVD authoring, and now we're using Sony DVD Architect. I cannot imagine this would make a difference as we never recompress the video once it's exported from out NLE system (VelocityQ). MPG2 exports are done with years old presets and we know the files are compliant, not to mention we've done scores of projects using these in the past without seeing this issue.

There have also been no software updates to the non-linear software since this cropped up.

The videos look fine when played on a software DVD player on a computer, even if it's scaled to fill the frame at high resolutions on an LCD monitor. So I have to think there's something going on with the 3:2 pulldown or with progressive scan to cause the issue on a hardware DVD player.

Could the 16x9 flag that instructs a DVD to letterbox for playback on a 4:3 TV be the culprit?? The aliasing isn't as bad when played on a 16x9 TV, but it's certainly there.

Thanks





Chris Blair
Magnetic Image, Inc.
Evansville, IN
http://www.videomi.com


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