Deinterlace for progressive?

[akrako1]

I've got a simple question (or maybe not that simple...)

I'm running my DVR-320 into my HDTV thru component video inputs, so I'm getting a proper progressive scan display. The TV supports it, and it looks damn nice. Here's my question, I do all my encoding with TMPGEnc. When I'm converting video for DVD use, should I always choose to de-interlace, and thus get a progressive picture? Is there any circumstance where de-interlacing would degrade the quality of the source?

Theoretically... if I converted interlaced video to non-interlace (progressive), and then played it on a non-progressive system, would the quality look the same, worse, or better than the original?

Thanks!!

[daamon]

Hi akrako1,

You'll need to confirm this by looking into how deinterlacing a source actually works, but my belief is that either the odd or the even fields are removed to produce the progressive picture. Clearly, if information is being removed, quality will be reduced.

Even if all the odd (or all the even) fields are replaced by interpolated fields and set to display progressively, the interpolation of the data will (probably) cause a reduction in actual quality.

As for whether you should encode to progressive or not - sorry, I can't help there. I'm not lucky enough to own a HDTV and so have no need to know this stuff...

What I will say is that it's not possible to make something look better than the original. That implies that extra information / data is being added. There are things that can be done to make the picture look better to the observer but technically speaking, it's not improving the actual quality, just the perceived quality.

Hope that helps some. Good luck...

[Baldrick]

deinterlacing is not authoring. moving you the advanced conversion forum.

[junkmalle]

All types of deinterlacing, except inverse telecine, degrade the picture.

[vhelp]

Theoretically... if I converted interlaced video to non-interlace
(progressive), and then played it on a non-progressive system, would the
quality look the same, worse, or better than the original?

It would (will) look worse. But, your bitrate will probably be better than
a bitrate distribution over an Interlaced source
.
The "worse" part, (about it) comes from method of de-interlace you use, hence
the blurryness. There are all sorts of various techniques to de-interlace,
and some are good, while others are poor, and yet, others are "worse".

But, fwiw..

de-interlacign a source (to progressive) will add a form of "strobbing"
when played back on a TV set. Test this out for yourself to see how far
your mileage go.

-vhelp 3280

[akrako1]

Thanks for the feedback. Does 'inverse telecine' really not degrade the picture, or introduce the strobing effect that vhelp mentioned? I seem to remember when using that filter, that the encoding time is significantly increased.

I guess it comes down to,.. (even if using inverse telecine) is there any benefit to de-interlacing an interlaced video clip for progressive viewing? Or should I just stick with the original interlacing setting of the source? Thanks!

[jeanl]

There's some interesting info in this thread. Look for edDV's answers. Your progressive TV is able to display interlaced material, and that's probably the best solution. That's what I remember from his posts.
jeanl

[junkmalle]

Does 'inverse telecine' really not degrade the picture, or introduce the strobing effect that vhelp mentioned?

Yes and no.

First of all, any time you convert to a lossy format you will lose some quality. If you use a high enough bit rate the loss can be negligible.

Secondly, inverse telecine will only work with film based movies that have been telecined. It converts the 59.94 field per second video back to the original 23.976 film frames per second. It will not work with live video footage like football games, local news, home camcorder footage, etc.

Thirdly, the IVTC has to be done properly. Otherwise some interlaced frames will get through or frames may be dropped. For the most part you have to have a movie that has been perfectly telecined (no breaks in the telecine pattern, no editing at the video stage, no commercials) and a perfect capture (no dropped frames). Otherwise you will have to spend a lot of time identifying the telecine pattern breaks and encoding in sections.

[jeanl]

junkmalle, this is a bit off topic, but can you clarify something for me? If you do inverse telecine, you end up with a video stream of 23.976 frames per seconds. What can you do with that? You can't watch it as is, right, because it's not NTSC or PAL. What would the next steps be then? A bit confused as you can see...
jeanl

[junkmalle]

junkmalle, this is a bit off topic, but can you clarify something for me? If you do inverse telecine, you end up with a video stream of 23.976 frames per seconds. What can you do with that? You can't watch it as is, right, because it's not NTSC or PAL. What would the next steps be then? A bit confused as you can see...
jeanl

You burn it to DVD marked for 3:2 pulldown. The VOB file on the DVD will be progressive 23.976 fps and the DVD player will perform the telecine for 29.97 fps interlaced devices. Most commercial movie DVDs are done this way.

[jeanl]

I see, now I get it. I suppose this is where the repeat_first_field flag is used in the MPEG headers. Thanks for that!
jeanl

[bugster]

If your source is interlaced, encode it as interlaced. Let the DVD Player or TV do the de-interlacing for a progressive display. It will do a much better job than any software will.

[akrako1]

If your source is interlaced, encode it as interlaced. Let the DVD Player or TV do the de-interlacing for a progressive display. It will do a much better job than any software will.

This seems to be the general consensous. I've never payed much attention to TMPGEnc's interlace/deinterlace setting before now... By default, will it keep the output video the same format (interlace or prog) as the original? Or should I be checking it every time?

Thanks for all the replies!

And jeanl, that link to your previous thread was very informative. Are you now totally happy with your dv->dvd encodes? Did you end up buying something new?

[jeanl]

No, I'm a happy camper. I realized that I wasn't looking at my interlaced DV video (encoded into MPEG2) with the right tools. Once I started using vdubmod to compare original and encoded on a field-by-field basis, things got much much better. I encode at about 6Mb/s, and at that level the encoders that I tested gave very similar results. In the end, it's more a question of convenience/price for me. But HC keeps on improving (there's a new version since my test), so I'm still watching!!
jeanl

[lenti_75]

get a progressive player, and leave the encoding interlaced.

[lbecque]

Interlaced vs. De-interlaced
There is a good guide and overview to this problem at:
http://www.digitalfaq.com/capture/interlace.htm

[akrako1]

Thanks for the link!

From the above source:

Telecine is a fake interlace used to make 24fps film appear normal on 29.97fps interlaced display devices like television sets. It can easily be removed with an IVTC (inverse Telecine) filter found in many software encoders. This will often restore the video to its original progressive state, as well as remove extra frames inserted to the Telecine process.

However, this being said, not all movies started as progressive film source.

IVTC will often still leave de-interlace artifacts, just not as many as a raw de-interlace. And once source has gone onto analog tape or broadcast, it is interlaced from then on. The telecine trick mainly works on converting existing DVD footage.

This seems to be the only instance where de-interlacing actually can improve the quality of the image we view. Does anybody know how to determine if the telecine filter was used in the first place? (ie a good candidate for running inverse-telecine)

By the way, Lenti_75, the dvr-320 is a progressive player. My other jvc dvd changer is progressive also.

[bugster]

Does anybody know how to determine if the telecine filter was used in the first place? (ie a good candidate for running inverse-telecine)

avi2dvd gives a good indication of this. If it says 'film' or a large percentage is film, it is a good candidate for IVTC.

[junkmalle]

Does anybody know how to determine if the telecine filter was used in the first place? (ie a good candidate for running inverse-telecine).

Open the file in VirtualDubMod. Seek to a point where there's some motion. Step through the frames using the arrow keys. A telecined movie will have a distinctive patter of 3 clear frames, 2 interlaced frames, repeated over and over.

[SLK001]

Is your original source really interlaced, or is it telecined?

The answer to this question makes a HUGE difference in what you do.

[pfh]

Does anybody know how to determine if the telecine filter was used in the first place? (ie a good candidate for running inverse-telecine).

Open the file in VirtualDubMod. Seek to a point where there's some motion. Step through the frames using the arrow keys. A telecined movie will have a distinctive patter of 3 clear frames, 2 interlaced frames, repeated over and over.

I've noticed the same effect when using Womble with commercial vhs source captures and came to the same conclusion.

Just for clarification- is a telecined vhs movie a progressive or interlaced source or neither? My thinking is, it's a telecined movie with 3:2 pulldown flags. Therefore as most of you stated- leave it as is and let the dvd player do the work for viewing on interlaced tv. It does get confusing.

[junkmalle]

Just for clarification- is a telecined vhs movie a progressive or interlaced source or neither?

You mean a commercial NTSC VHS tape of a film (or off-air recording of same)? VHS tape isn't much more than a simple analog recording of the linear signal that is sent to the TV. It must be 59.97 fields per second interlaced. So a film source has already been through a 3:2 pulldown when it's on VHS tape.

[marclile]

So i have a question then. is the following statement correct?

any video that i watch on my pc that has visible scan lines must be interlaced and if the video looks smooth and clear it must be progressive.

i know that if you watch the video with any DVD player software it should look smooth either way but windows media player does not automatically de-interlaced, right? so if i watch interlaced video in wmp then i should see the interlaced line?

[pfh]

junkmalle- I mean the retail commercial vhs tapes you buy (movie productions telecined onto tape).

When I use womble to display frame by frame I do notice the frame comparisons you spoke of. 3 frames are single and 2 are "interlaced" so to speak. But this is after capturing to mpeg2. I do know my capture device caps as progressive mpeg.

[edDV]

Thanks for the link!

From the above source:

Telecine is a fake interlace used to make 24fps film appear normal on 29.97fps interlaced display devices like television sets. It can easily be removed with an IVTC (inverse Telecine) filter found in many software encoders. This will often restore the video to its original progressive state, as well as remove extra frames inserted to the Telecine process.

However, this being said, not all movies started as progressive film source.

IVTC will often still leave de-interlace artifacts, just not as many as a raw de-interlace. And once source has gone onto analog tape or broadcast, it is interlaced from then on. The telecine trick mainly works on converting existing DVD footage.

This seems to be the only instance where de-interlacing actually can improve the quality of the image we view. Does anybody know how to determine if the telecine filter was used in the first place? (ie a good candidate for running inverse-telecine)

By the way, Lenti_75, the dvr-320 is a progressive player. My other jvc dvd changer is progressive also.

I think we need to review how a Progressive DVD player works. I think you will find that a good one, one with 3:2 detection, will do a superior job than software in most cases.
http://www.dvdfile.com/news/special_report/production_a_z/3_2_pulldown.htm
Also most progressive TV sets will convert interlace streams to progressive, most include 3:2 pulldown removal for movie material.

The progressive EDTV/HDTV display issues are handled well by a good progressive DVD player or the deinterlacer in the TV itself.

Typical PC software deinterlacing algorithms are crude and not intended for EDTV/HDTV display. Software deinterlacing is necessary only for the following reasons:

1. The target display will be a progressive computer monitor and there is no intention to play the file on a TV (or TV display quality compromise is assumed in favor of the computer display). This is the assumption made by those playing with DivX/XviD et al. whether they realize it or not.

2a. The goal is to achieve maximum compression. Compression algorithms like a progressive input.

2b. The goal is to process the image with a filter that requires a progressive raster.

3. Is there another reason?

Broadcasters and Post Houses do 2b all the time but with realtime hardware processors ($10,000 and up) that use motion adaptive deinterlacing algorithms that are either too sophisticated for a PC to process in reasonable times or are protected by patents. These devices usually will take an interlace input and produce an interlaced output with minimal artifacts. Even so, editors avoid a direct cut from the 1x input to the 1x output because you can see the quality difference.

Bottom Line: Edit and author it maintaining interlace and let the progressive DVD player or TV hardware make the progressive conversion. That is their job.

Products like PowerDVD will do a good realtime job of progressive computer display from an interlace source. If you want a better computer display solution, then investigate non-realtime de-interlace options as a separate project from the TV DVD.

[junkmalle]

any video that i watch on my pc that has visible scan lines must be interlaced

Yes.

and if the video looks smooth and clear it must be progressive.

Yes, but you have to be careful that both the player and the codec aren't deinterlacing. I have seen some codecs (MPEG and DV) that automatically deinterlace when uncompressing video on the PC. The codec's decoding configuration dialog often has a setting that lets you control this.

[junkmalle]

junkmalle- I mean the retail commercial vhs tapes you buy (movie productions telecined onto tape).

When I use womble to display frame by frame I do notice the frame comparisons you spoke of. 3 frames are single and 2 are "interlaced" so to speak.

Yes, commercial VHS tapes are telecined.

But this is after capturing to mpeg2. I do know my capture device caps as progressive mpeg.

I don't know what you mean by this. Is your capture device performing the IVTC to progressive 23.976 fps? Is it BOB deinterlacing? Is it drop-field or blend deinterlacing? If you see interlace comb lines your MPEG is interlaced.

[edDV]

Feature movies (35 and 70mm) are originally 24 frames per second progressive on film.

NTSC video is 60 fields per second, 30 frames per second. The fields are offset 1/60 sec in time. This 1/60 sec field offset is important for deinterlace algorithms.

To convert 24 fps film to 30 fps (60 fields per second) video, the 3:2 process (aka in computer circles as telecine*) is used. This process is adequately covered in the link above.
http://www.dvdfile.com/news/special_report/production_a_z/3_2_pulldown.htm

All film sources seen on NTSC broadcast, VHS, laserdisc, etc. have the 3:2 sequence. Reversing the 3:2 sequence can reconstitute the 24 fps progressive sequence. Other non-film TV sources are native 60 fields per second from a video camera.

Such video, either native film converted 3:2 or native TV will display fine on an interlace TV but look torn on a progressive computer display. Computer people seeing this torn video on their display, think something needs to be fixed. It doesn't if you intend to view it on a TV. In fact it's just what you want for a normal spec DVD that can be played interlace or progressive. "Fixing interlace" will just make the TV display worse.

Medium and up quality progressive DVD players and medium and up EDTV/HDTV sets know how to detect the presence of a film source and will automatically remove the 3:2 sequence, then deinterlace to 24 frames per second, then frame repeat a sequence to 30 or 60 frames per second (actually 29.97 or 59.94) for smooth display on a progressive EDTV or HDTV. If you spend minimum bucks, all this is built into your progressive player or TV.

Standard 60 field per second video can also be deinterlaced for progressive tv display but the quality issues are far more complicated since the native video was never progressive in the first place. You may see motion artifacts unless the 1/60 sec field motion offset is filtered in some way. The progressive image quality depends on how the 1/60 second motion is handled.

* in broadcast jargin, telecine is a projector to video sensor transfer process. It can range from simple mirrors to "aerial" lens technique to "Rank" style flying spot scanners. Computer people tend to use the term to indicate 3:2 (aka 2:3) pulldown process.

[pfh]

First off- there's been some really good threads here regarding telecine, progressive, interlace. And they've certainly aided me in video education. Thanks.

For my work I'm on a quest to better understand my source. My results are good but was mislead to believe that all vhs is interlaced and I have a capture card that outputs progressive mpeg no matter the source.


quote from Plextor support
"The Philips decoder chip we have in the 402U always captures interlaced video. This video is passed to the WIS encoder chip we use. This encoder chip and driver only supports de-interlaced video at this point so the video is converted from interlaced to de-interlaced video before it is encoded.

For MPEG-2 video, we support three types of conversion; Blending, Direct Waving and Interpolating. We use the Blending method by default which gives good results on still images and slow moving images. For fast moving images, the Interpolation method provides best results but this method is not great for still images. The Direct Waving method is great for still images but bad for slow and fast moving images. We will release a new driver in the next week or so and it will be set to Blending by default and will allow the user to change to any of the other methods depending on what type of video they normally capture. From the beta drivers we have sent out, about 50% of people have had their problems cleared up and they are very happy with the quality so we are making some progress."

To me, we have 3 basic types of sources- progressive, interlaced, and telecined.
If I understand it correctly, one can't call a telecined commercial vhs a fully interlaced source and therfore that's why my results don't display badly.
Either that or the engineers at Plextor are using some good voodoo.
Or more likely I'm not quite "gettin it" yet.!

nice link edDV..................

[edDV]

First off- there's been some really good threads here regarding telecine, progressive, interlace. And they've certainly aided me in video education. Thanks.

For my work I'm on a quest to better understand my source. My results are good but was mislead to believe that all vhs is interlaced and I have a capture card that outputs progressive mpeg no matter the source.


quote from Plextor support
"The Philips decoder chip we have in the 402U always captures interlaced video. This video is passed to the WIS encoder chip we use. This encoder chip and driver only supports de-interlaced video at this point so the video is converted from interlaced to de-interlaced video before it is encoded.

For MPEG-2 video, we support three types of conversion; Blending, Direct Waving and Interpolating. We use the Blending method by default which gives good results on still images and slow moving images. For fast moving images, the Interpolation method provides best results but this method is not great for still images. The Direct Waving method is great for still images but bad for slow and fast moving images. We will release a new driver in the next week or so and it will be set to Blending by default and will allow the user to change to any of the other methods depending on what type of video they normally capture. From the beta drivers we have sent out, about 50% of people have had their problems cleared up and they are very happy with the quality so we are making some progress."

To me, we have 3 basic types of sources- progressive, interlaced, and telecined.
If I understand it correctly, one can't call a telecined commercial vhs an interlaced source and therfore that's why my results don't display badly.
Either that or the engineers at Plextor are using some good voodoo.[/i]

Where to start. Tune in later this evening. I need to go home.