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Mark Beazley
IoHD questions
on Nov 21, 2008 at 2:28:28 pm

Some questions about dealing with HD formats and the IoHD.

Does the IoHD add setup automatically in ProRes 422? My understanding is even the gamma curve is a bit different but my research led me to believe the RGB equivalent values are still 16-235 like NTSC. I know these numbers represent 8bit values and 10bit supported -- I've actually been doing all my testing so far in 16bit projects rendering out Trillions of colors in AE.

When working in AfterEffects and rendering out to ProRes422 what color space do I use? Rec709 or Rec709 (16-235)? Should I keep the working space in AE at sRGB IEC61966-2.1? I see that the HDMI output and input can be set to 16-235 or 0-255; which is the proper one to use? Do I run HDMI in YUV or RGB space? I guess that may depend on the monitor used.

I noticed some sync issues when importing a still created in Photoshop (png format). My research revealed that inside the color scale 0 and 255 are used for sync -- which explains the Photoshop issue; but the issue continued even if I change the color space to either of the Rec709 spaces.

Regarding the above does AfterEffects automatically stay away from 0/255 because of the sync?

I currently do not have any clients doing HD -- but I want to make sure I know the scoop before they start demanding HD; and get all the headaches and gotchas out before hand.

My current plan is to pretty much do things in either 1080i29.97 or 720p59.94; is there any reason I should not be using these two (other than a specific request to use something else)?

-mark


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gary adcock
Re: IoHD questions
on Nov 21, 2008 at 5:59:37 pm

[Mark Beazley] "Does the IoHD add setup automatically in ProRes 422? "

there is no setup in HD.
What Gamma curves are you referring to? There are different colorspace between HD and SD but the gamma is the same.

[Mark Beazley] " I've actually been doing all my testing so far in 16bit projects rendering out Trillions of colors in AE. "
stop that Now- there is NO 16bit in video and you are causing more issues than not the CS3 version of AE has different rendering in RAM than on output, depending how many cores of your computer are being used ( with CS3 more was not better) the issue is not in Cs4

[Mark Beazley] "Rec709 (16-235)"
that would be a broadcast decision where you are clamping both the whites and the blacks - why would you want to trash your image before you start editing?

[Mark Beazley] "I noticed some sync issues when importing a still created in Photoshop (png format). My research revealed that inside the color scale 0 and 255 are used for sync"

Those were AUDIO sync issues are mostly related to - incomplete updates and audio at the wrong sample rate.

FYI your research is wrong- sync is in the VANC space which is not part of the image area -

Nearly everything you have talked about is with SD specs and the info and you want to do HD which is vastly different.


gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows

Inside look at the IoHD
http://library.creativecow.net/articles/adcock_gary/AJAIOHD.php




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Mark Beazley
Re: IoHD questions
on Nov 21, 2008 at 6:58:10 pm

So if I understand you correctly Gary, the black level in HD is 0 even on a waveform monitor; and in FCP. So basically I don't have to worry about any color or luma (255 whites) levels in After Effects as long as I render out using Rec709 color space?

The sync issue I am referring to is I had a png that I generated in photoshop; whenever I dropped that into my timeline and output through the Io, the video sync would go crazy -- video that I had already captured played back fine.

Why do you say to stop using 16bit color in AE; if I use 8bit then I will get banding on color gradients.

I just read a thread that came up in a search on this very forum about people wanting to render out from AfterEffects using trillions of colors to 10bit based video; which I assume would be from 16bit AfterEffects projects.

I appreciate your feedback since I am trying to learn as much as I can before I need start HD editing and get into trouble.

-mark








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