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Why encoders offer more field options than standard?

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Shawn Hyper
Why encoders offer more field options than standard?
on Aug 25, 2012 at 3:21:40 am

As we have known, DV kind of videos are bottom field first ( maybe should be called F2 dominant?), and others are top field first (F1 dominant?), but why when we render a file, the field setting of almost all the encoders has all the options - top first, bottom first and no field? How can it be?

If say, a file rendered using DV50 coder with top field first checked - which is contrary to the standard, then the file is imported into a NLE, will it confuse the NLE?


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Rafael Amador
Re: Why encoders offer more field options than standard?
on Aug 25, 2012 at 6:20:37 am

NTSC SD codecs (with little exception as the Aurora) are all Lower first (DV flavors and Uncompressed).
But in Pal-land is not like that. DV codecs are Lower, but Uncompressed and assimilated (Prores) are Upper first.
rafael

http://www.nagavideo.com


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Shawn Hyper
Re: Why encoders offer more field options than standard?
on Aug 25, 2012 at 6:38:29 am

Thanks for reply.

Maybe I haven't express myself clearly.

Here is an example, we'll render a sequence using DV codec, the DV codec has some settings, right? One of the settings is for field, you can choose up first, low first or no field. According to the standard, there should not be field option, since for DV, it's low first, and it should be hard-coded. Why the codec has other options?


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Rafael Amador
Re: Why encoders offer more field options than standard?
on Aug 25, 2012 at 10:59:47 am

[Shawn Hyper] "when we render a file, the field setting of almost all the encoders has all the options - top first, bottom first and no field? How can it be?"
In the "Sequence Setting" window you need to have every option in terms of size, aspect, pixels, field order, frame-rate.etc, etc, because the sequence needs to be fully customizable.
However if you export DV through QT, in the interface you will get Interlaced & Progressive options. But this is not to set a field order (QT do not manage field order), but to manage Chroma compression, that works different for interlaced than for progressive.

[Shawn Hyper] "According to the standard, there should not be field option, since for DV, it's low first"
The standard don't define the field order. If MiniDV (and DVCam) was Lower first, was for a matter of compatibility among the brands, and a was an agreement of the manufacturers.
Size, pixels aspect and compression scheme define the "quality" of a format. The field order is not a factor.
Anyway, you now the Panasonic-AG-DVX100. That was the first DV camcorder recording p24, and although records the signal as any other DV camcorder (29,97fps, Lower first), the footage (after removing the pull-down) is edited as Progressive. So you need, if not an Upper first, at least a DV Progressive option.
When SONY developed Digibeta, BetacamSX and IMX, they decided that the NTSC models to be Lower first and the PAL models to be Upper first. Why? No idea. May be to avoid hardware compatibility, but there are no technical reasons. I've asked few experts, and nobody had a cue on that.
rafael

http://www.nagavideo.com


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Shawn Hyper
Re: Why encoders offer more field options than standard?
on Aug 27, 2012 at 9:03:46 am

[Rafael Amador] But this is not to set a field order (QT do not manage field order), but to manage Chroma compression, that works different for interlaced than for progressive.


Thanks for explaination. I used to think that's for how to compress fields or frame.

Then the setting should be the same as the sequence? If it's upper first in the sequence, then it should be set upper first in the encoder? But waite, why for a DV sequence the setting can be upper first or no field?


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Rafael Amador
Re: Why encoders offer more field options than standard?
on Aug 27, 2012 at 12:27:06 pm

[Shawn Hyper] "Then the setting should be the same as the sequence? If it's upper first in the sequence, then it should be set upper first in the encoder? But waite, why for a DV sequence the setting can be upper first or no field?"
I don't catch this.
I guess you are talking about "QT Conversion".
With QT Conversion, in some codecs you have no option (Interlaced or Progressive).
In other codecs you can select Interlaced or Progressive, but when selecting Interlaced, you can not select Upper or Lower.
If you are talking about exporting a QT movie from the time-line (current settings), your Sequence Setting must match the footage field order, unless you apply a shift-fields filter or deinterlace the footage.
If you are editing DV, you can apply the shift-fields and set your sequence as Upper First. You will get a no-standard Upper First movie that will work without problem.
You can also deinterlace the footage and set your sequence field order NONE. You will get a DV Progressive movie.

[Shawn Hyper] ".. But waite, why for a DV sequence the setting can be upper first or no field?" Where do you get those options?
In the Sequence Setting, whatever the codec, you have always three options: Upper, lower and NONE.
But as I said, if you are editing Lower First stuff, you can't just change the Sequence field order to Upper or Progressive. That would mess all the picture.
rafael

http://www.nagavideo.com


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Shawn Hyper
Re: Why encoders offer more field options than standard?
on Aug 27, 2012 at 1:35:34 pm

Thanks, it's clearer now.

I just thought before that In the Sequence Setting, whatever the codec, we as users should not always have three options: Upper, lower and NONE. DV codec for example, it should be forced to lower first, we should have no option here.

If say a DV sequence, the setting is forced to lower first, then if we import a upper first footage, we can apply field-shift filter just as you said.

But in fact we can set a DV sequence to upper first, and we can adjust footage as needed. Then at last if we render the sequence to a QT movie using DV codec, the DV codec interface still have all the field options: Upper, lower and NONE. I wonder what will happen for each option in the DV codec?

Too Many Standards = No Standard = Chaos

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Pro Tools HD 1 v 8.1cs1


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Rafael Amador
Re: Why encoders offer more field options than standard?
on Aug 28, 2012 at 4:01:22 pm

[Shawn Hyper] "I just thought before that In the Sequence Setting, whatever the codec, we as users should not always have three options: Upper, lower and NONE. DV codec for example, it should be forced to lower first, we should have no option here."
yes, but the "Sequence setting" window is codec agnostic. and as I mentioned must be fully customizable.
Imagine that here in Pal-land I want to make an animation that I want to put later on on top of a video. I need to have all these options available because the video could be Lower (DV), Upper (DigiBeta) or Progressive. Any pro NLE or graphic application (PP, AVID, AE, Motion..) have the field order option no matter the codec you use. The same that must to have the same three options to identify (interpret) footage when importing. Most applications makes assumptions of the field order of the footage depending of the codec. FC by default will tag any DV stuff as Lower First, even if is Progressive or the field order has been shifted somewhere.

In the end is to the editor to know what is he doing when he change the field order.
The best policy is to don't mess there, but some times is needed.
For many years I've been editing DV footage and exporting it as 10 Uncompressed Lower first (to avoid recompression). In theory 10b in PAL should be Upper first, but as long as I was finishing in a DVD, was no problem because MPEG-2 for DVDS can be Upper or Lower. Of course, in the Compressor Inspector window, I had to check the file as "Lower First" otherwise Compressor would have taken that file as Upper First for being 10b Uncompressed.
If I wanted to print that to a DigiBeta tape, then I would have made a mess. DigiBeta in PAL is Upper First. You can change the field order of a file and the player will play it well if is aware of the correct field order, but you can't do that on a tape.

[Shawn Hyper] "Too Many Standards = No Standard = Chaos"
In the "analog" times was not this problem. The upper was always the first field because is the natural way to scan a picture (you would never start o read a text by the second line, don't you?).
At that time all the video/TV specs and standards were set by some international organizations (CCIR, EBU, ITU,..) participated by government agencies. Everything was about broadcast, so footage and hardware had to fallow the same standards in order to be exchanged and sold in different places.
With the digital boom, manufacturers started to set their own rules.
rafael

http://www.nagavideo.com


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Shawn Hyper
Re: Why encoders offer more field options than standard?
on Aug 29, 2012 at 2:17:56 am

Thanks a lot. I have learned a lot from you.

BTW, below is my signature. ;-)


Too Many Standards = No Standard = Chaos
FCP7, Mac OSX 10.7.4, BMD Multibridge Extreme
Pro Tools HD 1 v 8.1cs1


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