What is Interlacing?

Today's AVCHD cameras can shoot in interlaced or progressive mode. NTSC modes are 60i for interlaced and 24p for progressive. The PAL equivalents are 50i and 25p. Early AVCHD cameras were interlaced only.

Interlacing is the practice of displaying a single frame of video as two 'half' frames. Each frame is split into alternating lines, so that the first frame displays lines 1,3,5 and so on, while the second frame of the pair displays lines 2,4,6 and so on.

For all of the gory detail on why interlacing came about, read this Wikipedia article.

If you look at a raw interlaced clip converted by VoltaicHD for Mac, you will see the interlacing on playback. If you look at a clip from the same camera taken in progressive mode (24p or 25p), there will be no interlacing.

When you look at the same clip under iMovie or Final Cut, you won't see the interlacing. This is because the editor uses a small preview window and you won't notice the interlacing. When scaling a clip down in size by more than 50%, the video player will just drop every second frame, so the interlacing disappears. The underlying clip is still interlaced.

When you export your completed movie from iMovie, it will be deinterlaced for you automatically. If you are using Final Cut you will need to apply the Effects->Video Filters->Video->Deinterlace filter manually to your sequence timeline.

New AVCHD cameras generally have a progressive scan mode (e.g. 24p on NTSC, 25p on PAL) which is more 'HD friendly'. New cameras from Panasonic have 50fps and 60fps progressive modes, which are great for action movies. As the HD workflows mature, these will most probably become the standard.