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Io HD - Interlaced?

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matt robson
Io HD - Interlaced?
on Jan 5, 2008 at 10:27:46 am

Hi there I shot a project on HDCAM 25p and brought it in to FCP 6 via Io HD. However, the footage is all 25i now, I can't understand how this has happened! Did I get something wrong when I brought in the footage?


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Jeremy Garchow
Re: Io HD - Interlaced?
on Jan 5, 2008 at 7:36:14 pm

How'd you bring it in? What format? Are you sure the footage is 25p?


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Carsten Orlt
Re: Io HD - Interlaced?
on Jan 5, 2008 at 8:39:26 pm

As far as I know there is no 1080p25 ioHD preset.
All 1080 presets for 25/50 are interlaced.
I'm new to the whole HD thing so the following might be wrong. 1080 is always interlaced as of now and there is no true 1080p standard yet. progressive in 1080 is actually what is called PsF.
The naming conventions in HD are very confusing and it doesn't help that different companies use different terms for the same thing.
You can set your 1080i seq to 'none' for the field order and that effectively makes it p in the regard that there will be be no field rendering. You have to make some test yourself as I'm not sure yet about all the implications myself. I for instance shot 720p25 and post in 1080i25 (or 50 depending on the manufacturer). It gets interesting when you do speed changes. Because if you keep field rendering on you theoretically end up with an interlaced image....
Hope this helps (might create more questions too :-)


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gary adcock
Re: Io HD - Interlaced?
on Jan 5, 2008 at 9:17:55 pm

[Carsten Orlt] "As far as I know there is no 1080p25 ioHD preset."

it is EU truth in labeling - since it is not P but PsF that is recorded by virtually all 1080 cameras - and that always plays back as interlace on your monitors and set tops.

It is no different than the Kona cards are.

[Carsten Orlt] "I'm new to the whole HD thing so the following might be wrong. 1080 is always interlaced as of now and there is no true 1080p standard yet. progressive in 1080 is actually what is called PsF."

you may be new to this. however you do understand correctly.

"The naming conventions in HD are very confusing and it doesn't help that different companies use different terms for the same thing."

How true- why couldn't Sony adopt the 59.94 standard that every other camera maker uses instead of calling theirs 29.97


gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows
Inside look at the IoHD




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Jeremy Garchow
Re: Io HD - Interlaced?
on Jan 6, 2008 at 12:49:09 am

Matt. Are you seeing two distinct fields or are both fields of each frame the same?


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Matt Robson
Re: Io HD - Interlaced?
on Jan 6, 2008 at 11:13:52 pm

Interesting, very interesting thanks.

So basically, there is no point shooting 25p on HDCAM if I'm using the IoHD box, as it can't replicate it? Or is it that there is no such thing as 1080p right now?

Sorry this is confusing!

Thanks again.


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Jeremy Garchow
Re: Io HD - Interlaced?
on Jan 6, 2008 at 11:28:10 pm

You are getting confused and it's confusing...kind of. Progressive Segmented Frames are progressive frames in an interlaced wrapper. Both fields of the frame are the same so it looks progressive, it's just in an interlaced stream. SO yes, you can shoot 25p, even though it might be spitting out interlaced from the Kona. Turn your field rendering to none in FCP. That is why I asked you if both fields are the same or different. That will tell you if you even shot 25p or not.

Jeremy


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Matt Robson
Re: Io HD - Interlaced?
on Jan 7, 2008 at 9:28:03 am

- That is why I asked you if both fields are the same or different -

Apologies I missed that. Not sure how to check each field, when I set frames in the sequence to none, it seems to loose half it's resolution, which makes me think that it is perhaps interlaced.

Seeing as I'm clearly a bit new to this, is there an online resource somewhere that I can read that will perhaps explain all this, so that I can leave you good people in peace?!


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Jeremy Garchow
Re: Io HD - Interlaced?
on Jan 7, 2008 at 3:03:12 pm

Do you have an external monitor hooked up? If so open up the ioHD COntrol Panel and click the codec tab. Make sure the 'Full Frame' radio button is checked. When you go back to FCP you should see both fields on your external monitor. If you are willing to post a second or two of video in it's native form, I will be happy to take a look at it for you as well.


Jeremy


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Alan Lacey
Re: Io HD - Interlaced?
on Jan 7, 2008 at 4:24:56 pm

I'm confused about this PsF thing as well. If both 'fields' are identical isn't the data rate unnecessarily doubled?

Alan


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Jeremy Garchow
Re: Io HD - Interlaced?
on Jan 7, 2008 at 4:40:04 pm

No. As you are sending one field at at time (which is half of a frame). It's still 25 (or 30) frames a second, but it's 50 or 59.94 fields per second.


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cowcowcowcowcow
Carsten Orlt
Re: Io HD - Interlaced?
on Jan 7, 2008 at 8:13:36 pm

its really quite simple.
interlace means that that first the odd lines are written 1,3,5,7,9.....
and after that the even lines in a second run 2,4,6,8,10.....
In Pal this happens 50 times a second producing 25 complete frames per second.
Now imagine a camera chip that takes an exposure on each of those 50 cycles only writing either odd or even lines at a time, and you would look at one complete frame you would see a temporal difference between the odd and even lines (think of a ball flying left to right. the even lines would show the ball a bit more to the right then the odd lines on one frame)
But you can also expose all lines of the camera chip at the same time store the information in a temporary buffer and then write first the odd lines and then the even lines to tape. If you do this 25 times per second you effectively have a progressive frame. That it was is called Progressive segmented frame.


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Jeremy Garchow
Re: Io HD - Interlaced?
on Jan 7, 2008 at 8:39:52 pm

Well said, Poster Formerly known as Cofe.




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Dave Martin
Re: Io HD - Interlaced?
on Jan 8, 2008 at 3:41:28 am

>>>>>>Seeing as I'm clearly a bit new to this, is there an online resource somewhere that I can read that will perhaps explain all this, so that I can leave you good people in peace?! <<<<<<<<

Hear Hear!




Dave Martin

- MacPro - MacBook Pro -


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Jeremy Garchow
Re: Io HD - Interlaced?
on Jan 8, 2008 at 3:56:16 am

Start by searching here at the cow? There's a lot of information archived here.

Jeremy


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Alan Lacey
Re: Io HD - Interlaced?
on Jan 8, 2008 at 10:06:56 am

Arrrh! I see now! Thanks a lot for the explanantion.

Alan


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