Question about progressive, interlaced

[alfixdvd]

At the Doom9's guide : Getting the best out of CCE.

Where it comments the results of analyzing with BitRateViewer it says:

As you can see the Picture structure is frame which means the content is frame based rather than Field based, so you would check Progressive frames in CCE. The DCT type: Frame also points to this. If the content were interlaced the DCT type would by Field instead.

When you have a progressive source (Pic structure and DCT type = frame)

Well, with Alexander movie, PAL, Region 2, BitRateview give me the next data :

Num. of picture read: 126
Stream type: MPEG-2 MP@ML VBR
Resolution: 720*576
Aspect ratio: 16:9 Generic
Framerate: 25.00
Nom. bitrate: 7000000 Bit/Sec
VBV buffer size: 112
Constrained param. flag: No
Chroma format: 4:2:0
DCT precision: 8
Pic. structure: Frame
Field topfirst: Yes
DCT type: Frame
Quantscale: Nonlinear
Scan type: ZigZag
Frame type: Interlaced
Scene change detection: NOT FOUND
Variable GOP pattern: NOT FOUND


Pic. structure: Frame
DCT type: Frame
Scan type: ZigZag

Therefore Alexander is Progressive.

Why DvdRebuilder says is interlaced or alternate ?

I don't understand, please could anyone explain me ?

[onesoul]

You could have done a search, see this post (http://forum.doom9.org/showthread.php?p=661983#post661983) for example.

The guys over the big studios when doing the film conversion to PAL, are clicking the wrong buttons sometimes...

[alfixdvd]

BitRateViewer don't know how to analyze PAL ?

[communist]

It only reports what it reads in the file (checking if certain flags are set or not). Wether something is really interlaced or not can only be checked by really looking at the pictures sequence.

DVD authoring houses have set up their encoders and dont fiddle with the settings and since it doesnt hurt encoding progressive material with interlaced settings this isnt a big problem. In other words : they're to latzy to check the source and set the approriate settings and just encode everything as interlaced (which AFAIK only reduces compression efficiency if source isnt interlaced - but then again there's plenty of space on a DVD - hence its not big problem).

[jdobbs]

I don't really get the original point...

Bitrate viewer says the source is "interlaced" under frametype. So why would DVD-RB see it as anything other than "interlaced"?

If it were a progressive source, Bitrate Viewer would say "Progressive" under frametype.

Since it is interlaced, the alternate scan order is the preferred method. DVD-RB doesn't "see it as alternate", but has made the decision to encode it as alternate (because it is interlaced).

[onesoul]

jdobbs you make it sound almost as confusing as some of my posts ;).

[mrslacker]

@alfixdvd
It's clear why DVD-RB treats it as interlaced. As jdobbs said, it is flagged that way, so what else should DVD-RB do?

BitrateViewer's info is suggestive of a progressive source, but DCT Type and Picture Structure cannot be reliably used to identify a progressive sequence. There are two points to keep in mind:

1. For interlaced sequences, the encoder may decide on a frame by frame basis to use a frame picture or two field pictures. (i.e. Picture Structure)

2. In the case of an interlaced frame picture, the decision to use Frame or Field DCT coding is made on a macroblock-by-macroblock basis. (DCT Type)

So, what is Bitrate Viewer saying in telling you these two pieces of information? First frame/macroblock? Most occuring types?

The point is, Picture Structure and DCT Type won't tell you for sure if the sequence is progressive. On the flips side, if it reports Field DTC, it can't be progressive.

I think you are best off examining the movie for combing on moving areas of the picture. If you never find any, they you might check the "Ignore Interlaced" option for whatever VTS. I don't know the problems of PAL authoring, but that's what I hear on the grape vine (http://forum.doom9.org/showthread.php?t=74356). ;)

[jdobbs]

Unfortunately when people examine for combing they usually do it on their computer -- which typically doesn't handle interlaced sources worth a damn. Also at least half of the times I've had someone voice concerns about seeing combing and wanting to "deinterlace", a further investigation found that they were actually talking about a progressive source and the combing they saw was caused by telecining...

In other words there are a lot of people who are trying to "deinterlace" progressive sources, and make judgement calls based upon what they see on a computer monitor -- and it all has no basis in fact.

Bottom line: If the person wanting to make changes doesn't understand this stuff absolutely completely -- it is much better to let DVD-RB do its job and quit mucking with it...

I'd estimate that 90% of all bad encodes are self-inflicted wounds -- caused by the best of intentions but a lack of knowledge in trying to "help" DVD-RB out.

[mrslacker]

These concerns should probably be detailed in a sticky or something. The importance of examining raw frames over displayed frames for one... Turning off your software deinterlacer for another... The things not necessarily exclusive to DVD-RB but particularly important in its proper use. This could be something as simple as "Make d2v with Raw Encoded Frames field operation. Make avs. Step through in media player classic, with interlacing method set to Weave. Pay attention to moving areas."

That might lead to more confusion, but it might at least prompt inexperienced users to start second guessing their approach instead of blaming it on you. If there is no mystery about it, there will be less false positives for you to address. just a thought. Best.

[Rockas]

The main problem is the kind of developer that gives too much information about his software... http://www.thestylemachine.com/smileys/uy.gif

[alfixdvd]

I think that to give a lot of information never is too much, the knowledge does us better

[SkVid]

@ jdobbs
alfixdvd just asked a question. He didn't complain about your software.
Maybe it wasn't your day when you answered his post.
What I like about your Rebuilder is that I have the possibility to see what he does and try to understand. During the rebuilding phase this is impossible for me. Too much is going on inside. But it reveals the prepare phase as well as the encoding phase. And those who are intressted take a deeper look at it. Questions are just a conclusion. This board is the place where we can get the answers. And this is why your software contrasts pleasantly with all other one-click-solutions.

I saw many questions about interlaced material. I once asked about tff/bff. Maybe you should add another FAQ about this kind of stuff, something generall. :)

[alfixdvd]

@ jdobbs
alfixdvd just asked a question. He didn't complain about your software.
Maybe it wasn't your day when you answered his post.


Thanks Skvid. I have not given importance the comment out of tone. I only want to understand. I think a forum it's a great place to do.

[jdobbs]

If you saw any "tone" in my response you misread it... and I apologize. I'm not trying to be confontational, but just stating that your conclusions in the first post were incorrect. If the source were progressive, Bitrate Viewer would have output the word "Progressive" under "Frame Type"...

When I said "I don't really get the original post" that's what I meant.

[Rockas]

I think that to give a lot of information never is too much, the knowledge does us better
I agree with you... as long as "I keep in mind that I must be carefull about what I will be doing with the information", know what I mean?

Sometimes people don't use wisely the info they get (I'm not saying that this is the case here... but if you take a tour around this forum you be seing many posts about self inflicted errors from people that simply read, but don't understand, the Info).

Let me give you an example... Nero Recode... isn't it possible that it has some hidden settings?... probably have... but do we know any? (well I don't... I don't us it :))