I am editing an HDV timeline but adding some DV footage using FCS 6 on Snow Leopard. If I change the clip speed of the DV footage in a DV timeline, it renders fine (see "good-DV" attachment). However, if I do the same thing in an HDV timeline, I get a judder as shown in the "bad-HDV" attachment. Applying the de-interlacing filter does nothing to address the problem (I tried all variations). Also, the problem only happens if I select "Blending" in the Clip Speed popup.

Any ideas to make it work? TIA

That looks like a field order problem. Check the clip. Did Final Cut automatically add a "switch fields" filter to the DV clip? If so, remove it.

Though actually, HDV and DV have opposite field orders, so I would expect that you should ADD the switch fields fiter to the DV material (on an HDV timeline) in order to get rid of your problem.

When adding the DV clip to the HDV timeline, FCP adds a switch (-1) field filter. Removing it does not fix the problem. Adding a de-interlace (Upper-Odd) after rendering the clip does not solve the problem. I have attached clip of the source DV footage.

Do the clips have the same framerate?

Yes. All clips are 29.97FPS in the original.

I'm stumped....

Have you tried bringing it into another sequence?

You could try exporting a self contained movie from the DV sequence with the time change & then re-import it.

Chris's post is the correct workflow for FCP; you can't import a differing codec than the original sequence settings and do a time remap of any kind and have it "conform" properly. Do your speed change to the DV clip outside the original sequence, either in a separate timeline or, in Motion, then import that *pre-rendered* clip into FCP. Note that if you attempt to cut that imported clip and then re-render you'll end up with the same judder problem again.