[MacDV] Re: iMovie HD bugs

[Matti Haveri]

Jan E. Schotsman:

>  Sounds like a lot of deinterlace-related bugs in iMovie 5.

Yes. Jan, you are the expert in interlacing. Do you have any idea 
what is behind these iMovie interlacing bugs? Are they scaling bugs 
in QuickTime or in the Timeline Movie.mov??

JES Deinterlacer can be used as a workaround for the Slow-motion and 
Reversed Effects bug (see below #2).

There are at least five interlacing-related bugs:

1. The worst bug is the interlacing distortion when adding titles or 
effects because the workarounds are so bad. The bug is clearly 
visible in moving scenes.

The error can be seen in both fields in NTSC. In PAL there seems to 
be something wrong with every 8th even field, and the distortion can 
be best seen by deinterlacing off the odd fields. Here are images 
illustrating the problem in NTSC and PAL (188 and 290 KB, View at 
100% size to best see the distortion in interlacing lines after 
iMovie HD titles are added). BTW, the NTSC sample is a clip from the 
old iMovie Tutorial.

<http://www.sjoki.uta.fi/~shmhav/iMovie_HD_title_distortion_NTSC.jpg>
<http://www.sjoki.uta.fi/~shmhav/iMovie_HD_title_distortion.jpg>

Notice how before adding a title the interlacing lines are correctly 
and evenly distributed, just how they should be. After adding titles, 
the interlacing pattern is distorted and this can be seen as 
artifacts also when viewed on a TV.

Workarounds: a) dont use titles, b) use titles only on footage with 
no motion, c) or revert to iMovie 4.0.1!

The titles and effects bug smells like a QT scaling bug with the 
reference Timeline Movie.mov:

I noticed that I get EXACTLY the same distortion in the interlacing 
pattern if I save the iMovie_project/Cache/Timeline Movie.mov as .dv 
via QT Player with the "High Quality Enabled" playback setting ON 
(and the other playback settings unchecked). (It is odd that the QT 
Player's playback quality setting affects the exported video quality, 
i.e. whether fields blending is used etc). I then noticed that the 
PAL Timeline Movie.mov is automatically stretched as 784x576 for 
viewing (when iMovie's "Show Full Video Resolution" is ON). If I 
resize the QT Player window to 720x576, THEN the exported .dv's 
interlacing is OK. The same applies to NTSC: the NTSC Timeline 
Movie.mov is stretched as 720x528 for "Full Video Resolution" viewing 
-- resizing to 720x480 fixes the interlacing in the exported .dv).

2. When iMovie HD slows down a clip (0.5-0.2x), it doesn't anymore 
deinterlace it like iMovie 4 did. This can be seen as flicker when 
watched on an interlaced TV. The error can be best seen in 0.2x 
slow-motion.

When iMovie HD reverses a clip, it doesn't anymore change its field 
dominance like iMovie 4 did. This can be seen as flicker when watched 
on an interlaced TV.

Workarounds: You get smoother slow-motion with 3rd party applications 
so slow-motion clips don't need iMovie's rendering. JES Deinterlacer 
can also change the field dominance in reversed clips.

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