Friday, August 26, 2016

Re: [Avid-L2] Safe Color doesn't unrender with color correction change etc...?

 

Funny you should mention that.  I just saw that option for the first time today while dicking around trying to scale 4096x2160 "True Pain in the Ass 4K" and I noticed the legalizer in the effects tab in my recently updated AME.  I usually run AME CC 2014 on an older startup drive and I don't recall seeing that feature in the effects tab.  Today on my 8.5.2 startup drive OS 10.9.5 I am running AME CC 2015 the latest update.  Was the Legalizer effect always there in all the previous CC 2015 options?


As I look at the controls they seem to have very confusing values in the parameters to my dinosaur view.   
Signal (Min/Max): -30 130
I understand what min and max are but what are the values -30 and 130 referring to in terms of units?  -30 IRE, millivolts or what.

Similarly confusing it the:
Shadow: 64  10
Highlight: 192  10
The help pop up says "Sets Threshold and softness for darker values. Threshold adjusts the lower limit for darker values, Softness adjusts the boundary between tonal ranges"  Same thing for Lighter values on the highlight parameter.

So WTF is softness between tonal ranges?  I think of a clipper/legalizer softness as how harsh a clip it makes not the boundary of tonal ranges.  I look at a value of 64 for the shadow and that makes sense as 64 is the 0 millivolt equivalent in 10 bit to 16 in 8 bit but then WTF is 192 a value of for the highlights.

How am I suppose to monitor the effects of this legalizer/limit function?  Is there a way to have AME feed out to a real scope and broadcast monitor so I can tell what I'm effecting and adjusting? \

I will have to look deeper into the help manuals on this but the reality is this is just not the way I can work efficiently or effectively.  I need a real time output to monitor the final signal so I can see and detect issues and either modify color correction or tweak some form of Safe Color Limiter.

I would think it would make more sense to have legalizer effect parameters for shadows at 64 and 940 to correspond to Rec 709 10 bit values but clearly there is some other analysis methodology at play here.  It escapes me how these parameter make sense in any traditional method of critical level analysis.  I'm probably just not akin to the Adobeology that is at play here.  Do these parameters track with other metrics in the Adobe eco system?  

---In Avid-L2@yahoogroups.com, <pale.edit@...> wrote :

Not to add more complexity to this, but have you attempted to use Adobe Media Encoder's video legalizer (foregoing the Avid one)?  Just curious.

On Friday, August 26, 2016, bigfish@... [Avid-L2] <Avid-L2@yahoogroups.com> wrote:
 

You bring up an interesting point about changing codecs.  Even with tape I found when I scope the Avid out directly I can run my Tek scope alarms at 0% area setting and not log errors.  If I instead I scope the output of the HDCam or HDCamSR deck I have to set the area parameter in the for gamut to 1% or the alarms light up like Christmas time.  My understanding is the compression and then subsequent enhancement circuits on the a

decks cause tiny specular errors that trigger the scope alarms. 

You mention changing codecs as causing shat seems to be similar issues.  I have found just taking a 23.976 file in dnx220X and other resolutions and adding pulldown will also start the scope flagging errors.  IIRC even just doing a mixdown in avid and going into a 59.94 project with the motion adapters added the exact same video essence and codec that played in the 23.976 project without alarm at 0% suddenly shows alarms when the pulldown is being added.  I'm not sure why this happens but it does. 

Perhaps the motion adapter isn't clean in some form.  I do know if I take color bars signal from 23.976 and bring that into a 59.94 project I get jiggy jaggies in the waveform display but if I import the exact same test pattern still while in the 59.94 project the resulting bars are clean of the jiggy jaggies.  I assume the same is happening to the video following the same path.  If I use Adobe Media Encoder to add the pulldown it the resulting file still seems to display the alarm issues so I don't really know if it's the Avid time warp jiggy jaggies or something in the nature of adding pulldown.  For the life of me I don't understand how adding pulldown should change to video in a manner that suddenly triggers the scope alarms for gamut.



---In Avid-L2@yahoogroups.com, <pat@...> wrote :

With the massive shift to file based delivery you need a file based legalising solution. Playout and recapture is one route but its defeating much of what filebased output saves.
A proper grade is key to ensuring levels are legal to start with of course. Then avids safe color limiter with 422 selected (no point in legalising with it not working its hardest) but experience shows some content xan still be illegal even with the safe color limiter applied. That then needs manual correction.
The change in codec is often the issue so dnx185x to AVC intra as we need to gor UK deliverables can throw an issue.
We have tge AQC of the final output as a check for Gamut errors and more and an eyeball QC of the final timeline with scopes etc as the human check.
Worth noting that there are alternatives to the safe color limiter that offer more broadcast options like R103 and even soft clippers. Be good if the Avid safe color limiter was upgraded to offer similar options. And even better if it had a mode that could do the limiting so that the codec change to follow was safe as well.

Pat from his mobile.

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this is the Avid-L2

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