Interlaced vs. Progressive

[FoxGarrison]

Can anybody please explain the difference between Interlaced and Progressive encoding? I've looked at all the docs and seem to understand that interlaced is better when encoding but, I'm not sure why. I always thought that interlaced was obsolete given computer screens are generally non-interlaced. Help!

[DivXExpert]

http://www.doom9.org/synch.htm
Nice little article, hope it solves you problems.

[FoxGarrison]

I've checked out the link, thanks. I'm still in the dark about this all. If I make the the rip interlaced will it look better than progressive? If so, why?

[banjazzer]

VCD is not interlaced. SVCD can be interlaced. If the source DVD is interlaced and you are creating SVCD then it will be useful to produce interlaced SVCD. The reason being that by de-interlacing you are losing video information. If you are producing VCD then you must de-interlace. If the source is progressive (ie not interlaced) then you can forget about interlace alogether when encoding VCD or SVCD.

[FoxGarrison]

The reason being that by de-interlacing you are losing video information. If you are producing VCD then you must de-interlace.

So, if I de-interlace then I would be losing quality...why would I want to de-interlace a VCD from DVD if I'll be losing quality? I would like to improve the quality, wouldn't I?

Sorry for pressing this issue, I'm just trying to understand the quality factor regarding interlaced VCDs.

[vitualis]

Because VCDs, which use MPEG-1 doesn't support interlacing at all. It only supports progressive frames.

You cannot physically make an "interlaced" VCD.

From a truly interlaced source (e.g., a TV show), you could end up with interlacing artifacts if you simply converted the interlaced fields into progressive frames. No only do these look bad, they cause sharp lines and edges in the picture which also chews up bitrate --> blockiness.

Thus, you should probably de-interlace first.

However, from DVD, although the video is still stored as interlaced fields, the frames themselves are often progressive (for NTSC -- as 23.976 fps FILM frames and for PAL as 25 fps frames). Thus, no deinterlacing is necessary (or should be done).

If the video on the DVD is truly interlaced, then deinterlacing may not be a bad idea. It at the same time may not be necessary as for VCD you will also be reducing the vertical dimension by a half. This in effect "blends" both fields into one.

My suggestion is to try it out for yourself and see what your EYES tell you.

Regards.

[FoxGarrison]

Thanks, vitualis...I'll try it out!