Sunday, May 8, 2016

Re: [Avid-L2] Re: Is Avid RGB export of DNX-175X media really RGB in video essence level?

 

The project settings seem to have been modified since 8.3.1.  Now the color space is listed as a separate choice whereas in 8.3.1 there was a laundry list of projects that included color spaces.  I think you can still change the color space in the projects in 8.3.1 but I've never had to deal with this until 4K.

I also noticed there is a separate color space setting in Video Output which can slave to the project or be set differently.  In the Video output you can select RGB Full Range and the output to the scope reflects what I would consider the Avid classic RGB level of 0 to 255.  There are also all kinds of YCbCr color spaces along with RGB, 20/20 and Aces in various flavors.  Anything other than YCbCr send out whacky signals to the scope and monitor.  By whacky I mean not what they want to see.

I finally hooked up my client monitor component out of the NitresDX and got that to work to some degree.  My program Ref Monitor has no component in.  I did find that when I'm in 23.976 and try to do a cross convert to 59.94 the output component and Nitris DX disappear until I turn cross convert off.  I even toggled Hardware off and on but no output with cross convert on.  I have adopted the process of turning on cross convert to send HDMI to my client monitor as it doesn't accept Psf but now that there is the ability to set HDMI and Component out to True Progressive I can see the output on the client monitor feed component and I assume HDMI but I haven't tried the HDMI when running 8.5.2.

It is rather confusing in nomenclature when Avid uses RGB to represent Full Range in some cases and others it's to represent bit depth.  I beginning to think this is a big part of my misunderstanding all these new project settings.  I had thought if I had 444 sources, that I believe are RGB uncompressed signals (please correct me on this if that is wrong) that's when I would choose an RGB project.  I'm not really understanding what project parameters dictate what project choice. 

Dave you say you run in "RGB" so you get full 444 and not 422 in Avid.  Your Avid media is still 709 levels but 444.  Why do you need 444 RGB?  Is it because of your source material or what you have to export to?  In the case of Netflix which want BT.709 YUV I'm covered with my standard 709 project and monitoring.  Well except for the part where I don't have a 4K monitor or scope but it should track from my 709 HD downconvert for monitoring and color correction

I had always thought in an RGB 444 project the video essence would be Full Range/Full Swing but from what your saying Avid still scales those sources to 709 levels.  How is this effected by media the Avid treats as native vs. transcoded media.  I would expect that if I ama link to 444 RGB material and transcode to DNxHRHQX that media would be scaled to legal 709 or not based on the source settings on the clip.  If I don't say scale to legal in those settings and I transcode won't the media then be video essence that is Full Swing?  I really need to hammer on the Avid High Res workflow guide.



---In avid-l2@yahoogroups.com, <mactvman@...> wrote :

One more idea... Make the MXF OP1a out of avid, open it in Resolve on a Mac and export to ProRes there.

And you mentioned monitoring...

In the previous solution, levels and monitoring would be with your normal scopes, as you only add the color lut to push to full range at the last stage of export.

In Resolve, it works internally in full range.  I don't have Resolve with a Blackmagic appliance, so I don't know how that works.

Dave Hogan
Burbank, CA


On Saturday, May 7, 2016 1:04 AM, "Dave Hogan mactvman@... [Avid-L2]" <Avid-L2@yahoogroups.com> wrote:


 
I work on a daily basis using "RGB" project settings in the AVID  (Currently in v8.3.1).  To be clear, and many probably already know this, the AVID project setting for RGB vs YRB is only about bit resolution of each channel.  AVID still functions ONLY in 601/709 colorspace INSIDE the AVID.

Clipster uses a terminology of FULL vs HEADSPACE, to indicate that in the former, you have black at zero and white at max.  In 8 bit that would be 0 and 255.  In 10 bit it.s 0 and 1027.

So there are two different kinds of RGB when discussing the AVID.  When you set your colorspace in the project settings to RGB, you still have headroom on black and white, it's just that you have 3 full channels of full range and 10 bit resolution (Red, Green & Blue).  In this setting we have only two resolutions in 1080p, DNxHD 440 and Uncompressed.  Both are 10 bit only.

When switching to YRB (4:2:2) you have both of your color difference channels half sampled, and all but your max DNX resolution are 8 bit, and you have a choice on uncompressed of 8 or 10 bit.  (the unmarked one being 8 bit).

Now I have run into MANY inconsistencies when trying to create full range RGB QuickTimes.  The AVID is consistently inconsistent in this manner.  I have done exports with the same settings, and had them work right sometimes and wrong others.

Michael Phillips has tackled this problem in two ways, in the following post.  First he recommends creating exports using the MXF OP1a export, to get reliable exports of AVID resolution you require.  To get full range, you just apply a color lut to the timeline you are exporting, and it will bump the levels to full range.

I don't know how far back these features go, or if you have access to a current version of MC for your exports, but this is a simple and reliable way to export from the AVID, and get full range levels.

Hope this is of some assistance,

Dave Hogan
Burbank, CA







On Friday, May 6, 2016 6:45 PM, "bigfish@... [Avid-L2]" <Avid-L2@yahoogroups.com> wrote:


 
Wow I sent this one yesterday and it shows up now.  I've notice my last reply to this thread from today hasn't popped up either but others have from today and now this one shows up from yesterday.  Funky town on the internet.


---In avid-l2@yahoogroups.com, <bigfish@...> wrote :

I've asked several forms of this question in the past but today I have a specific request from the truck engineers for a live show we are prepping playback elements for.  For starters we've shot primarily with Alexa, I know that horrible camera that isn't even Netflix 4K worthy, but we are doing HD 23.976 transcoding to DNX 175X for offline and online given our quick turn around.  We are baking in the LogC to Rec 709 LUT and all looks fine.  We always work Rec 709 in Avid as it's the broadcast standard for all our deliveries.

Now the truck person wants us to deliver 59.94i files in DNX-145 8 bit RGB files.  Well for starters DNX-145 is only 8 bit so that is a no brainer.  59.94i is also understandable as this will be a live broadcast in the US.  It's the RGB that is confusing me.  I have done the mixdown in the 23.976 project to DNX 115, which I assume it the DNX-145 equivalent just like DNX-175X is the DNX-220X equivalent, and then opened a 59.94i with all the motion adapters and modification to the mixdown sequence.  I then export a QT movie with custom set to DNX-145 Upper field and click RGB to comply with the requests.  Now the resulting file is 59.94i but when I ama link to it the levels of color bars come back in perfectly.  Given it is an Avid codec I have no ability to change the source settings from 709 to RGB to see if there is a difference.  Given I've always understood the ama link to bypass the QT engine and therefore display the true video essence of a file I would expect if I had truly exported to RGB levelsI would be seeing color bars going way below 0 millivolts and way over 700 mV just like I do when an RGB level file is imported as if it is 709 and not scaled into legal range.  Doesn't this mean the real video essence in the supposedly RGB exported file is still 709 levels. 

I also used Adobe Media Encoder sending a QT ref file from the 23.976 project and setting it's levels to RGB and also a 2nd QT ref set to 709.  Once baked out of AME with the pulldown added the QT Ref exported at RGB level comes back ama linked in Avid at perfect levels while the QT Ref exported with 709 level checked comes back ama linked low in level.  This behavior is common for me when using AME so I always check RGB when exporting QT ref to AME.  Bottom line is once again the RGB exported QT ref once processed in AME yield the correct levels when ama linked back into Avid.  So to me that means the actual video essence is still 709.

I'm waiting to hear back if the AME file will be acceptable.  I'm beginning to think that the behavior I see in AME with regards to checking RGB vs 709 level is indicative of how other types of software read files and maybe the gear on the truck needs the metadata flag set to RGB to properly handle a file which is really 709 in video essence.  I'll report back when I find out but apparently the truck person is being very uncooperative about questions as to why they want a "RGB" file and not the ubiquitous 709 standard that is what the network that is airing the live show wants when we give them files.  What kind of truck playback system doesn't work with 709 video levels?  I also get suspicious of tech specs that request DNX-145 8 bit given 145 is only 8 bit.  What's next a tip penetration spec on the file?

On a related topic.  I never work in RGB projects as all my work is broadcast but if I were to work in an RGB project how do I properly monitor that in my Tek wfm-7020 and Rec 709 program monitor.  I see when I'm running Ver 8.5.2 when I change the project color space things change drastically with 2020 shifting hue on the vector scope, which is the way the math works as far as I know.  When I switch to and RGB project the levels jump well below 0 and over 700 so what is one to do when scoping and RGB show.  I will have to look but I don't recall and RGB mode on my scope, something akin to choosing 100 percent bars over 75 percent in the vector scope setting.  And what would be a compelling reason to work in RGB space.  I think that is common in 444 projects but I don't have in practical experience or need to work those projects yet.
 
John Moore Barking Trout Productions Studio City, CA bigfish@...




__._,_.___
Posted by: bigfish@pacbell.net
Reply via web post • Reply to sender • Reply to group • Start a New Topic • Messages in this topic (20)
this is the Avid-L2

.

__,_._,___
Posted by Video Geek Squad at 6:38 PM

No comments:

Post a Comment

Subscribe to: Post Comments (Atom)