Interlace or Progressive??

[Browncoat]

I have an ADVC100 which I use to capture home video off my camcorder, I then convert the DV to DVD compliant mpg and author it to a DVDR. I recently started using Tmpgenc 4 Express which I reckon is great. Tmpgenc gives me the option of making the mpg as progressive or interlaced. What do you, my video guru pals, recommend?

[jagabo]

Interlaced.

[Browncoat]

erm.. I was kinda hoping for a "why" as well.

[guns1inger]

Interlaced video is shot at 50 (PAL)/60 (NTSC) fields per second (OK, not quite, but it makes the numbers easier to read), with each field taken 1/50th or 1/60th of a second apart. During motion, the two fields do no line up exactly, which isn't really a problem because when they are displayed on an interlaced device - a CRT TV, for example - they are never on the screen at the same time.

When you deinterlace the fields to get a single frame, the two fields have to be blended together in some manner. Most deinterlacers choose a single method (or have a choice or a number of methods, but can only use one at a time) to do this, however none of them do a great job. Some throw away one field, and stretch the other to full height. Some just blur the two fields together. Some are smarter than that, but ultimately all of them do more harm than good.

If you have an interlace display device then you see the video as it was shot. If you have a progressive display device then the hardware built-in to it will do a much better and smarter job of deinterlacing on the fly than you can do in software, and you don't have to irrevocably damage your video to get it happening.

A little extra reading if you want it

http://www.100fps.com/

[Browncoat]

Thanks as always gunslinger.

[RickA]

Very well put guns1inger. Props to you. I usually learn something valuable from your posts, thanks. I knew it was generally not good to de-interlace but not exactly why.


@browncoat, you a Firefly fan?

Cheers,
Rick

[shashidar]

I have KWorld TV Tuner/Capture card. I connect my cable box audio/video out to inputs of this card for capturing. (I don't use TV Tuner as I record paid channel)
Looks like this capture card gives progressive NTSC DVD out. (only one preset for NTSC DVD).
(built in mpeg2 hardware does the video encoding, audio comes through the sound card)

When I burn it on to DVD I think it goes as progressive. But my standalone DVD player (Pioneer DV-333) is not progressive and I have LCD 720p TV connected on component video.

How this combination works ? Are there any interlace/de-interlace problems ?

I also have Sony SR200 camcorder, which I think gives interlaced NTSC out in 16:9 format.

Please explain.

[jagabo]

Interlaced video is broadcast (or travels down the wires) as a series of fields. Each field is half a picture. One field contains all the even numbered scanlines, the other all the odd scanlines. You see one field a time on an interlaced display, 60 different fields per second on an NTSC TV. There are no frames in an analog NTSC signal.

When interlaced video is captured by a digital device pairs of fields are woven together to make frames. If the picture was different between those two fields there will be obvious interlace "comb" artifacts when viewed on a progressive computer monitor.

When sent to an interlaced TV the two fields in each frame are sent to the TV one at a time, restoring the original sequence of fields.

If your capture device is deinterlacing the incoming video into progressive frames, those frames now contain one picture, not two half-pictures. when these are sent to the interlaced TV they will still be sent one field at a time. But by deinterlacing the source you have halved the temporal resolution. Instead of the 60 fields per second representing 60 different pictures they will represent only 30 pictures. In addition, deinterlacing generally introduces artifacts (there is no perfect way of creating one full picture from two half-pictures).

The situation is further exacerbated with film sources which are 24 frames per second. After being telecined for broadcast, then deinterlaced by the caputre card they will play noticably less smoothly -- one film frame out of every 4 is displayed twice creating six little jerks per second.

[shashidar]

Thanks for the info.

[Browncoat]

RickA Posted: Jan 31, 2008 07:30

@browncoat, you a Firefly fan?

Cheers,
Rick

Sure am.

Firefly is the best TV show ever made. Why Fox killed it i'll never know..