To Interlace or Not To Interlace?

[freak_in_cage_10k]

Hi All,

i use dvd2svcd and CCE 2.50 to produce high quality CVDs. at a maximum i have 1hr of video onto each cd-r. It the conversion tab there is a setting allow me to interlace the material. i am pretty sure that the option here depends on the input.

i am using UK pal dvds, normal movies, not music vids or n e thing.

my question is, should i use any interlacing settings? if it depends on my source, how do i know whether the source is interlaced or not? i have looked on several devd boxes and none of them mension them being interlaced (or not)

cheers a lot eveyone, all comments welcome

[vhelp]

.
.
well, if you want to know if your source is Interlaced.., then just open up
vdub w/ your source and scan through those scenes that you are going
to encode. If you see those "lines" in movements (ie, hands, body etc)
in "every" frame, then you know your source is Interlaced.

If you notice the scenes in your source is 3p, 2i (3 progressive, and 2
Interlaced) then you now know that your source is Telecined (aka, Film)
and as a result, you can utilize an IVTC step in your encoding process.

IVTC you can use...
* TMPG's
* decomb (for AVIsynth scripts)
* decomb (for vdub)
* pulldown (for AVIsynth scripts) (though, this is quite rough, and not recommended)
* and maybe a few other IVTC alternatives (sofware packages etc)

Ok, I just realize you said PAL region. I'm not sure how to correctly identify those.

Good luck thus far.
-vhelp

[freak_in_cage_10k]

ok, cheers all the same m8, any one else know how i can tell???

[DivXExpert]

Not sure, but i think all pal matierial is purely interlaced. Never seen progressive pal.

I am probably wrong though.

[freak_in_cage_10k]

hmmmmmmmmm, ok, so assuming that the source is interlaced what setting should i use in dvd2svcd?

are you sure that the source is interlaced?

cheers everyone!

[txpharoah]

Most of my PAL DVDs seem to be progressive, at least the ones from the UK. Just match your source.

[Epi]

Check out this website, it deals mostly with PAL and De-Interlacing. It's a long read but very good information (someone did thier homework).

http://www.100fps.com/

-Epi

[freak_in_cage_10k]

kool, cheers epi dude!!! i will check it out!

[freak_in_cage_10k]

i have looked at the site extensivly and it is very good & concise. however, the main problem is not what to do if the source is interlaced, but establishing whether my uk pal dvds are interlaced in the first place!?

is it justrandom or are the vast majority interlaced? all are normal movies, no music vids or home footage or anything.

anywaone else know how i can find out??

[flaninacupboard]

freak in cage,
films on PAL DVS's are progressive. they take the 24fps progressive film original, and speed it upt to 25fps, keeping it progressive. if you open up the DVD's in some kind of mpeg properties viewer they are often reported as being "interlaced" and while the encode mode is interlaced, the actual material is progressive.

in other words, if it's a feature film, you want to encode in progressive. if it's anything else (say fawlty towers or father ted) then it's probably interlaced. to make sure, watch the DVD on your computer. if you see the interlace lines, it's interlaced and you should use interlace mode. if there are no interlace lines you can encode in progressive.

Vhelp,
sorry, teleclining doesn't apply to PAL! never ever will i (or freak in cage!) have to analyse a telecline pattern

[freak_in_cage_10k]

flaninacupboard- ok, cheers a lot dude, so, in short:

no pal material is interlaced, except perhaps old comedies such as faulty towers, only fools & horses, rising damp etc right???

cheers dude!

[flaninacupboard]

pretty much yeah. most poeple over here have been using progressive video since they started using 16X9. there is the odd exception, so with a TV series, it's always worth checking. you should always check the credits too, Spaced was shot on progressive 16X9, but the end credits are interlaced. how irritating!

[SatStorm]

The reconstruction of the progressive source in PAL material is possible, but you won't see any benefits visualy.
With NTSC it does a huge visual difference but with PAL, just keep it as it is!

[SLK001]

VHELP was correct in his response above. PAL movies are usually made by speeding up a 24fps movie to 25fps. There also is a telecined version of PAL, with a 24:1 ratio, but these are pretty rare. Some video cameras put out a purely interlaced video, and no amount of processing can convert this to progressive (this is the "every frame has lines in movement" scenario). Also, captures of live TV events (like sports events) are almost purely interlaced at 25fps.

So, to recap, just examine your source frame-by-frame. If you see the "interlaced lines" every frame, then use the INTERLACE option (also, ALTERNATE SCAN). If you see only one frame that appears interlaced in 25, then you can either IVTC the sequence and process as progressive, or ignore the interlaced frame and just process as progressive (if you do the former, you will somehow have to re-insert the proper PULLDOWN flags for the video to play properly - there is no program to do this for PAL that I am aware of).

As a "rule of thumb", if your video was once released in a movie theater, your source is almost for sure 24fps PROGRESSIVE.

[freak_in_cage_10k]

ok, cheers everyone

[LisaB]

Hi,

I have to disagree with Vhelp about interlace lines.

You see, flaninacupboard makes a very important distinction between the "material" and the "encode mode". The existence of interlace lines (when examining frame by frame) says nothing about whether your source is encoded as interlaced or progressive.

The lines will tell you about the *material* (i.e., the ultimate source) but doesn't give you a clue as to the *encoding mode*. As far as I know, the encode mode is a *physical* thing...if something is encoded as interlaced, then the MPEG structure is actually encoded on a field-by-field basis.

Encoding on a field-by-field basis is a really good thing to do in the case of interlaced material, since in interlaced material, every field represents a distinct instant in time. If you put together two fields to make a frame, then there will be interlace lines in the motion parts. If you then encode the two fields together,*as a frame*, the jagged edges will be inefficient to encode.

If you are dealing with progressive material, then I don't think it makes *any* difference which encode mode you use -- the output will be the same visually, and the efficiency of the encode will not be affected. If you encode as non-interlaced, then your software DVD player will play the frames as-is, but your hardware DVD player will separate the frames into fields and send the fields to your TV at 50 fields-per-second. If you encode as interlaced, then your software DVD player will combine the fields into frames and display the video at 25 frames-per-second, but your hardware DVD player will just send the decoded fields as-is to your TV.

So, it's true that interlaced material should be encoded as interlaced. But that doesn't keep some idiot from coming along and encoding it as non-interlaced. Once interlaced material is encoded as non-interlaced, there is no going back. I'm just going on intuition here, but any compression will necessarily "blend" the fields, so you'll never really be able to get your fields back. For this reason, if your source has been encoded as non-interlaced, then there is probably little advantage in choosing interlace encode mode, even if the *material* is interlaced. Of course, there's also no advantage in encoding as non-interlaced!

Final conclusion: there's never an advantage to choosing non-interlace encode mode, whatever may be the *material* and *encode mode* of your source (and there are clearly 4 possible combinations here). So, make it easy on yourself and always choose interlaced encode mode.

I'm really hoping this dialog will be continued, as I have found very little information on this topic, and much of what I've said above is based on assumptions and speculations based on what I have learned. A little verification would be nice...especially from someone who is an expert on MPEG format, or how standalone DVD players process differently encoded material.

[vhelp]

@ LisaB..

Encoding on a field-by-field basis is a really good thing to do in the case of interlaced material, since in interlaced material, every field represents a distinct instant in time. If you put together two fields to make a frame, then there will be interlace lines in the motion parts. If you then encode the two fields together,*as a frame*, the jagged edges will be inefficient to encode.

Actually, I think that, that is what I have ben saying here (else, deffin.
at other threads/topics) !! Anyways..

I think you got this topic mixed w/ another topic you ment to pick
on me about !! Anyways..

Either the above is true about your mixed topic, OR, you are not clear
what IVTC is all about (weather progressive to you, or Interlaced Lines
to you)

3P, 2I.. .. ..
* Well, 3p means, 3 progressive frames, and
* 2i means, 2 Interlaced frames

You do NOT want to encode these frames as is, w/ Interlaced turned on
(assuming in) TMPG !! Period !! As, this will give you what's ben known
as GHOSTing (those 2i frames) in your final encodes, when you play it on
your DVD player and observe it on your TV set.
What you WANT, is to encode w/ an IVTC filter, and non-Interlace mode in
TMPG. Unfortunately, TMPG's built-in IVTC filter has some bugs, and will
actually throw in some Interlace, causing you to beleive you are correct,
and I am wrong !!
What you DO WANT, is to use AVIsynth and decomb.dll for your IVTC filter.
This produces no errors in your final encode, and ALL frames as true progresive !!

I'm sure that someone else here can guide you better than I could ever,
about Telecined video sources, and performing an IVTC in your encoding.

You must have missed something. Sorry. I'm not afraid to admit when
I'm wrong, and have I have done so on many occasions and even when those
who want to do this intensionally to me Anyways..

I do hope someone can explain better to you about this (and your statement)
and perhaps, you can make a revision in your statement to me ??

In any case, have a good day/weekend anyways.. we all deserve it
-vhelp

[LisaB]

VHelp, I'm neither confused about the topic, nor trying to pick on anyone...just trying to figure some things out that seem to be explained nowhere.

Sorry if I misinterpreted, but I think it's not clear what people mean when they ask the question "is the source interlaced". I mean, are they talking about the ultimate source of the material, or the encode mode of the material? If you look carefully frame by frame, yes you can figure out whether the material is interlaced or progressive or telecined. But, you can't tell looking at the frames whether the encode mode is interlace or non-interlace (of course if you are looking at MPEG1 it has to be non-interlace).

Anyway, you said you could tell whether a source was interlaced or not by looking at the frames. If you were referring to the material then yes, but if you were referring to the encode mode, then no.

Anyway, do you know if there is ever occassion to use non-interlace encode mode when making an MPEG2?

[vhelp]

@ LisaB..

Sorry if I misinterpreted, but I think it's not clear what people mean when they ask the question "is the source interlaced".

Yes, I agree. They do confuse most people. But, over the years, I've
become more wiser, and understand what/where most these peoples are
comming from.

Interlace or non-Interlace...
When people talk about "it's Interlace" for instance, they too, do not
fully specify what they are talking about, becuase they actually are
not telling us all what the source truely is (they can't tell at the
moment) All they see is some Intelraced lines. Don't mean that they
see it in EVERY frame, but that they see it just the same. Don't matter
to them much. Just that they SEE IT. So, when they talk about "my
source is Interlaced" they are in a sense, "generically" speaking of
Interlace.. well, sort of. Anyways..

So, next time you hear people talking about Interlace, put on your
wise hat, and either ASK them to verify exactly WHERE in their source
is the Interlace, and HOW OFTEN to they see it. Chances are, it's
a Movie that they captured and are seeing some Intelace.

Anyway, you said you could tell whether a source was interlaced or not by looking at the frames. If you were referring to the material then yes, but if you were referring to the encode mode, then no.

Yes, this is easy. First, (in this excercise) you must have vdub opened
w/ your source file loaded. Then, to know the following, do..

* A - how do I know if my source is PURE Interlace (every frame)
* B - how do I know if my source is Film (aka, Telecined) or (every 3P, 2I)

...
* open in vdub, your source .AVI file (untouched)
* scan through your source file to the point that you want to verify what
...your source is. That's the video range you want to encode.
* in order to see w/ more accuracy, right-click inside video time-line
...and select 2x size to increase video size. This will help
...to observe more clearly what the frame are showing.
* when you're at a point in your video (again, the parts you want to encode)
...start to (right cursor) each frame, and observe for Interlace.
.
PURE Interlace...
.
If you find that EVERY frame is Interlace, then you have struk gold.
Your source is Interlace every frame and you now have a choice to either
encode your source as Interlace (MPEG-2) or de-Interlace your source
hence, non-Interlace. De-Interlacing is a choice. That will depend on
a number of factors, which I'll spare you. YOU have to come to that
point. You already know about MPEG-1's limitation w/ Interlace - - It
doesn't support it. Thus, you know you do NOT have a film source that
you captured. Film being, Hollywood Movies. Ok, now for Film detection..
.
FILM... (most people still refer to this as Interlace lines, so be wise)
.
...You want to observe your frames for the following pattern, as you
...already know.. 3P, 2i frames.
.
So, lets say you are seeing 3 progressive frames (clean frames) and 2 Interlace
frames (distorted frames) When you see this type of pattern in your
source, then you know you have a Telecined (Film) source that you captured.
For these, you'll want to perform an IVTC, which, in short, will turn your
captured 29.970 fps into a 23.976 fps during the encoding. So, now you
have a 23.976 fps for encoding (if you used AVIsynth for the IVTC filter
process)
Thus, your frame rate will now be 23.976.
Under TMPG, if you selected the option for "3:2 pulldown", you will STILL
have a 23.976 fps, BUT, when you author and burn to CDR/DVDR disk, and
play it in your DVD player, your dvd player will duplicate 2 frames, hence
making it Interlace again, but only for your TV, while your are viewing it.
This is done on the fly, by your DVD player. But, remember, your burned
CDR/DVDR's Movie is STILL 23.976 fps. You DVD player, as I said, will
duplicate 2 frames, making it appear to be 29.976 fps.

So, the next time you hear (read) that someone is complaing about some
Interlace lines in their source, just assume that they are begginers
and don't know exactly what they have in there hands.. which could be
Interlaced (every frame Interlaced) or Telecined (aka Film, every frame
is 3p, 2i) ..they probably don't know what they have, never will you,
unless you can see beyond mountains and so on and so forth.

oh, this is w/ respect to NTSC sources. I don't know much about PAL
sources.. and these are slightly different. But, if you are in NTSC
world, then you needn't worry or bother w/ PAL sources, since these
are not really in these parts (though some people will find ways to
get their hands on some PAL sources)

I hope that help to claify some things.

Anyway, you said you could tell whether a source was interlaced or not by looking at the frames. If you were referring to the material then yes, but if you were referring to the encode mode, then no.

I'm not sure I copy that..

have a good evening.
-vhelp

[LisaB]

Okay Vhelp, here is a little experiment:

Take a small AVI file, completely progressive, and with no sign of interlace anywhere. Encode the avi to MPEG2 using TMPGEnc. Do one encode using "Interlace" encode mode, and one encode using "Non-Interlace" encode mode. If you open these two clips up in VDub, I don't think you will be able to tell which is which.

Take another small AVI file, true interlace, with interlace artifacts in every frame. Encode the avi to MPEG2 using TMPGEnc. Do one encode using "Interlace" encode mode, and one encode using "Non-Interlace" encode mode. If you open these two clips up in VDub, I don't think you will be able to tell which is which.

The point of this experiment, and the point I was trying to make earlier, is that I don't think you can tell whether a source is frame-based or field-based by examining the frames in VDub. The only way I know how to determine this is to open the source in TMPGEnc, and it will identify the source as either interlace or non-interlace. TMPGEnc is not talking about the material, but only the encode mode of the source.

Now, if TMPGEnc does see that the source is field-based, it will then try to determine the field-order (at least if you're using the TMPGEnc Wizard), and it actually spends time examing to try and figure out TFF or BFF. I think TMPGEnc doesn't always get this right, but it tries. If the source is pure progressive, then this is a total waste of time, because it doesn't matter which field is displayed first.

VHelp, you seem to know a lot about IVTC. I also like and prefer the decomb.dll and AviSynth. But sometimes I get a source which has clearly been telecined (3-2 pattern), but which has also been run through a deinterlacing filter. So in this case there are no sharp interlace lines, but rather a "3 sharp frames - 2 blurry frames" pattern. I usually just leave such sources alone, since I don't see how you could possibly reconstruct a progressive frame once the fields have been blurred. Would you stil suggest trying IVTC?

[vhelp]

@ LisaB..

I'm having issues my internet connect (connects, dissconects, all this
weekend) anyways.. Just so you know..

Take a small AVI file, completely progressive, and with no sign of interlace anywhere. Encode the avi to MPEG2 using TMPGEnc. Do one encode using "Interlace" encode mode, and one encode using "Non-Interlace" encode mode. If you open these two clips up in VDub, I don't think you will be able to tell which is which.

Take another small AVI file, true interlace, with interlace artifacts in every frame. Encode the avi to MPEG2 using TMPGEnc. Do one encode using "Interlace" encode mode, and one encode using "Non-Interlace" encode mode. If you open these two clips up in VDub, I don't think you will be able to tell which is which.

I'm not sure why you would want to know this at all. Either you know your
source, or you don't. If this is your own source, but you forgot, and now
need to expeirement to know how YOU encoded (Interlace or non-Interlaced)
than I don't understand why you need to go this route still. So, you can
see I'm confused why you even need to know this at all. Bottom line is
like this.. Either you run your source thorugh vdub and observe how the
frames are (EVEN if they are not so good quality (fuzzy etc)) or what-haveyou.
Only, that you have to try each scenario to see which will "finally" produce
the best (which what you got) assuming then, that it's an encode from else
where's. Are these issues all because of some divX/xVid files you D/L'ed,
or what ?? In the end, and as I have ben startin to notice, that people are
NOW just doing their own encodes (based on THEIR OWN) capturing etc.
Really, not to put your (or anyone else down) but IMO, these types of clips
that one has to deal with would not even be worth my time and effort, when
I got lots of other less probablematic sources (not that I have none to start)...
But, of course, you are your own boss
As I said, I wouldn't even both these type of clips (assuming they are D/L
clips and things) If they are yours, then you shouldn't even be having this
issues.

As far as knowing the source type as either being Interlace or non-Interlace
via TMPG...

* If you encode an Interlace as an non-Interlace, it will still be Interlaced,
...unless you included a de-Interlace step.
* If you encode an non-interlace as Interlace, you will see a non-Interlace
...output

But, then again, performing the above is only giving cause to issues in your
source materials if you're following this reckless pattern - not that you are,
but just in case. I'm going to assume that you don't, but that you are finding
sources like this. My answer to these types of encodes are like this, I
would simply buy the VHS tape (very least) and just do it myself and be
happier. But, of course, they could be sources that you can't get your
hands on.

but which has also been run through a deinterlacing filter. So in this case there are no sharp interlace lines, but rather a "3 sharp frames - 2 blurry frames" pattern. I usually just leave such sources alone, since I don't see how you could possibly reconstruct a progressive frame once the fields have been blurred. Would you stil suggest trying IVTC?

The only way to know for sure, is to just try this out for yourself.

-vhelp

[flaninacupboard]

Vhelp, i believe LisaB is talking about MPEG sources rather than AVI sources, and more specifically DVD. She (i guess?) is correct in that there -is- a difference between the material (interlace Telecline or progressive) and the MPEG encode mode (interlace or non-interlace)
Let me give you an example, until fairly recently progressive PAL DVD did not exist, so since the launch of DVD all PAL discs with featrure films (25fps progressive source) were encoded in interlace mode. this should never have happened, but it did. what also happened is that film makers decided "well, the discs are interlaced anyway, so we'll make the credits and some of the special effects interlaced to make them look better on a TV!"
This means if you re-encode the movie using progressive mode (which should be right, film is progressive) you get a terrible picture during the credits and the interlaced effects shots, so you should use interlace as the encode mode in this instance.

LisaB,
i use progressive a lot! lots of TV shows here are shot on progressive video (then broadcast and captured in interlace mode) then encoded as progressive. i also use it on any feature films without the credits/effects problem.

[vhelp]

@ flaninacupboard..

ok, so I guess this is a good example of mixtures (interlace etc) but I still
don't understand whta the problem is. I pretty much described the method
of determining Interlace etc. I'm not assuming that once a pattern is found,
that the user continues, "but w/ THAT pattern only". Its assumed that if
there are other areas to process, weather encoding, denoising, filtering,
or finding more Intelrace or what-haveyou, then, the user would continue
as such. I do understand that source can be a mixture of any kind of
pattern for Intelace etc, and be it from a Capture source or DVD source.
Doesn't matter. If there's Interlace here, and then Telecining there, and
then Progressive way over there, then the user makes this determination
per their finding, and continues w/ the processing of those areas in the source!! That's all.

Otherwise, I must be confused still.

Be good.
-vhelp

[LisaB]

flaninacupboard,

I was talking about both MPEG2 and AVI sources. Now, someone has said in a different thread I believe that AVI's are always frame-based, but I don't see how that can be so, since some AVI's that I open up in TMPGEnc show up as Interlace even though looking at the frames in VDub they seem progressive. TMPGEnc's behavior tells me that it chooses Interlace or Non-Interlace Source based on whether the source is field-based or frame-based. I still have yet to have someone verify that field-based AVI's exist...but the must, or else I'm really confused.

Is there any problem with encoding progressive material in Interlace mode? You say you do it with mostly progressive films to avoid the "credits" issue. But even with a purely progressive material, I don't see how it could hurt. I'm wondering if Non-Interlace encode mode is faster, or more efficient (bitrate-wise). That might be the reason to prefer Non-Interlace encode mode for a purely progressive source material....any ideas? And what about the case I talk about in the previous paragraph - progressive material encoded as Interlace. Should I go ahead and use Non-Interlace encode mode for that, too?

[flaninacupboard]

Lisa,
download the program Bitrate viewer from the tools section. this proggie tells you whether MPEGS are interlaced or progressive, the scanning type and the field order. i always just use the same settings i find in bit rate viewer.
As for AVI, i was under the impression that it was a progressive only affair. given that the playback device will always be a PC, there's no need for interlace. the exception here seems to be DV, which is interlace, or at least the incoming video is interlaced, even if it's recorded to tape as progressive. the only other place i could see as an exception would be mpeg4 (or the hacked derivatives, Divx Xvid etc) because MPEG2 supports interlace, does MPEG4? or is it restricted by AVI structure?