Questions and Poorly Informed Assumptions about Deinterlaced Footage

[Matt McLain]

If I'm right, I understand that shooting with an XL1s produces 29.97 interlaced frames a second, and that when I'm capturing that footage in Adobe Premiere I'm capturing it interlaced.

Via Magic Bullet I know I can convert that footage to 30p, which I believe means thirty full frames of footage per second.

I've heard that regular North American TVs and HDTVs and DVD players all play interlaced footage. So, if I burn 30p footage to a DVD will that DVD play on a standard DVD player hooked up to a standard HDTV?

If not, why deinterlace footage if it's not intended for Film. If your end product is going to be DVD, why deinterlace at all?

I've also heard that the "jaggy edge" problem common to most digital video is caused by interlaced footage, and the way to fix that is to deinterlace. Is that true? And if so, what are you supposed to do if your end product is going to be DVD?

Sorry this post isn't as organized as I would've liked it to be. As you can see, I'm not sure what to do about deinterlacing footage, or what it's implications are.

Thanks for the help.

[Dylan Pank]

Originally Posted by Matt McLain

If I'm right, I understand that shooting with an XL1s produces 29.97 interlaced frames a second, and that when I'm capturing that footage in Adobe Premiere I'm capturing it interlaced.

True, though there is the frame movie mode, which de-interlaces footage before capture. The image is de-interlaced though I believe the stream is still interlaced (or at least in "Progressive Segmented frames)

Via Magic Bullet I know I can convert that footage to 30p, which I believe means thirty full frames of footage per second.

Also true, though actually it's still 29.97 unless you tell it to speed up the footage too.

I've heard that regular North American TVs and HDTVs and DVD players all play interlaced footage.

Also true, but DVD players can also play progressive footage, they can scan it out as interlace. The more expensive ones (and many cheaper ones) can also output it as progressive footage if the source is also progressive (as your de-interlaced 30p footage would be).

So, if I burn 30p footage to a DVD will that DVD play on a standard DVD player hooked up to a standard HDTV?

Yes it will, the DVD player will either output it as an interlaced signal (though the actually frames will be progressive) or it can output a progressive signal that can be read correctly by a progressive scan TV.

If not, why deinterlace footage if it's not intended for Film. If your end product is going to be DVD, why deinterlace at all?

Good question.

There are three answers.

• it's a matter of taste. Film footage is "progressive" in the same way that 30p footage is progressive and many people just prefer that look.
• Some DVD players can only deal with upper field first signals, and some software based MPEG2 encoders (such as Quicktime MPEG2 component) can only pass through the same field order as the signal they get (which if the footage is DV 60i is LOWER field first) which means you get a horrible flickery image. De-interlacing means you avoid this as progressive footage can be unproblematically handled as upper field first footage even if technically the stream is lower field first. These days, pretty much ALL DVD players can tell read field order correctly, provided the encoder set the field order properly when authoring the DVD.
• and the third has to do with...

I've also heard that the "jaggy edge" problem common to most digital video is caused by interlaced footage, and the way to fix that is to deinterlace. Is that true? And if so, what are you supposed to do if your end product is going to be DVD?

This is true if your footage will play on progressive only monitors, basically computer screens. The jagged edges come about because the fields are not separated and appear as comb-edges. TVs don't show this because CRT TVs are inherently designed for interlaced playback, and flatscreen TVs while inherently progressive are designed to handle interlaced footage when they get fed it.

Sorry this post isn't as organized as I would've liked it to be. As you can see, I'm not sure what to do about deinterlacing footage, or what it's implications are.

Basically if you like the look of interlaced footage then don't deinterlace, but make sure, when you author the DVD, that you get the MPEG2 field order correct (i.e. lower field first).

If you are uploading to the internet, deinterlace.


Thanks for the help.

[Matt McLain]

Thanks Dylan. I read your answer pretty much right when you posted it and never did get around to thanking you. The response was incredibly helpful. Thanks again.