FORUMS: list search recent posts

Help needed with HDCAM SR Broadcast deliverables

COW Forums : AJA Video Systems

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
David Margolis
Help needed with HDCAM SR Broadcast deliverables
on Mar 4, 2010 at 6:23:54 pm

Hi all. I have a broadcast deliverable that was just rejected by a QC facility for having sub blacks and illegal luminance levels... even on the colour bars.

This project was output from FCP as Prores 444 to HDCAM SR 444 SQ 24PsF. We used the Kona card linking to a Sony SRW 5000.

We also did a digital beta version from the exact same source that did not have any of these problems.

Our scopes show no illegal values in the FCP timeline and FCPs range check (although I know it's not super reliable) shows a green tick all the way through.

We don't have access to the SR tape to check it at the moment. But does anybody have any idea what might have happened to our levels?

Thanks guys

David


Return to posts index

Jeremy Garchow
Re: Help needed with HDCAM SR Broadcast deliverables
on Mar 4, 2010 at 8:07:02 pm

Sounds like a gamma shift.

Do you have external scopes?


Return to posts index

David Margolis
Re: Help needed with HDCAM SR Broadcast deliverables
on Mar 4, 2010 at 8:22:17 pm

Hi. Unfortunately we don't have external scopes (bad I know) But I think you hit the nail on the head. It is a gamma issue. Before we sent the tape off we captured a small clip from it. Comparing it to the FCP timeline it's brighter. Not by a lot. But perhaps enough to mess up all our broadcast safe levels.

I changed video processing to Always Render in RGB and that seems to have fixed it.

That's really annoying! Why is FCP shifting the gamma in this way?



Return to posts index


Bob Zelin
Re: Help needed with HDCAM SR Broadcast deliverables
on Mar 4, 2010 at 9:34:56 pm

what kind of scopes are you using. If you want to play in the big leagues, you need the same gear "they" have. You need them to tell you what TC # the errors are occuring, and check on your scope for the same thing. For all I know, you have no problem, and it's THEIR problem - then you get on the phone and start yelling. Without pro HD scopes, you will not be able to tell anything.

Bob Zelin




Return to posts index

David Margolis
Re: Help needed with HDCAM SR Broadcast deliverables
on Mar 4, 2010 at 9:47:41 pm

The QC facility decided not to go ahead when they realised that even the colour bars were illegal. They were kind enough to give us another chance to submit something. So as soon as I get the tape back from them I can check.

As far as I can tell, this is a YUV / RGB thing. The moment I put the timeline into YUV everything goes bright.

From what I've read, this is a known issue with Prores 444.


Return to posts index

gary adcock
Re: Help needed with HDCAM SR Broadcast deliverables
on Mar 4, 2010 at 11:01:37 pm

[David Margolis] "This project was output from FCP as Prores 444 to HDCAM SR 444 SQ 24PsF. We used the Kona card linking to a Sony SRW 5000. "

OK

you think it is a gamma issue, Why?
at what point did you go from RGB to YUV?

you have to walk thru the entire workflow to confirm that.

What was the original content?
How was is handled?
What other apps touched it.

I think you don;t think of Gamma issues and much as you may have inadvertently added "setup" or had the dual link connection to the deck was incorrectly handled.

gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows for the Digitally Inclined
Chicago, IL

http://blogs.creativecow.net/24640



Return to posts index


David Margolis
Re: Help needed with HDCAM SR Broadcast deliverables
on Mar 5, 2010 at 12:20:48 am

Hey Garry. Thanks for responding. The pipeline has been as follows...

REC709 TIFFs from DI facility

TIFFs then went to DCDM for a DCP encode and also to ProRes444 (all from Shake)

I can absolutely confirm that the ProRes 444 output from Shake was identical to to the original TIFFs. I did an A/B check on them within Shake. No difference.

Prores settings were - 24p, 1920x1080. They went into a matching sequence in FCP.

The only thing I changed in the sequence setting was to render using YUV which I think is what caused the problem. When I switch YUV on the gamma is up too high. When I turn it onto RGB everything looks correct. And I'm talking here about FCPs output, not the internal viewer. Everything looks normal in the viewer no matter what video processing setting I use.

Of course, until I get the tape back I can't fully confirm this. But it seems the most likely explanation to me. The digibeta that passed QC (rendered from the same ProRes source) was set to RGB video processing.

My understanding of dual SDI setup is that so long as your deck is set to receive 444SQ, you can only really go wrong by having the A and B SDIs the wrong way round. Or having one not plugged in. And when either of those happen, it's pretty obvious it's not working correctly.

So that's why I'm thinking gamma. Then again, the QC guys reported sub blacks. Can incorrect gamma cause this?








Return to posts index

gary adcock
Re: Help needed with HDCAM SR Broadcast deliverables
on Mar 5, 2010 at 2:47:47 pm

[David Margolis] "I can absolutely confirm that the ProRes 444 output from Shake was identical to to the original TIFFs. I did an A/B check on them within Shake. No difference. "

So you only checked on your computer monitor? See Shake would do this correctly- it was when you output that it becomes an issue.

"REC709 TIFFs from DI facility "
those would be RGB files.

"The only thing I changed in the sequence setting was to render using YUV which I think is what caused the problem."
GONG!!!! you get a prize- you should have let the deck do the YUV conversion UNLESS you are on a CLEAN INSTALL of Snow Leopard (10.6.2)


"Can incorrect gamma cause this? "
the Gamma issue can cause differing results depending on the workflow, and where the conversions are invoked -
My guess is the deck saw black below 0 and attempted to compensate - you never mention which SR deck we are talking about - the first gen of SRW5000 series that have not been undated/ serviced could experience issues similar to this.




gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows for the Digitally Inclined
Chicago, IL

http://blogs.creativecow.net/24640



Return to posts index

David Margolis
Re: Help needed with HDCAM SR Broadcast deliverables
on Mar 5, 2010 at 9:50:27 pm

Gary, thanks for this. The deck is SRW 5500.

And I do have the latest version of Snow Leopard with all the updates.

So I got my tape back from the QC facility. Now I'm really confused. I view the colour bars on the tape looking at external scopes. The facility are correct. The bars (100% and generated from FCP) have blacks at -10. Bad. However, I capture the tape and PING everything looks normal in FCP. Apart from a slight gamma shift which was caused by the YUV incorrect setting.

So, I've changed everything to RGB. I've output to tape again. Settings on the deck are 24PsF 1080 4:4:4 SQ HDCAM SR. I'm going dual link into the deck from a Kona card which is set up correctly. Black and burst is set up correctly. I've been through all my settings in FCP and everything is correct. However, I output my bars again. They look fine on the scopes. Then I play back on the tape and everything is still illegal. Black are still at -10.

This must be something the deck is doing. I'm not all that familiar with the SRW-5500. Does anybody know what might be causing this?

David


Return to posts index


David Margolis
Re: Help needed with HDCAM SR Broadcast deliverables
on Mar 6, 2010 at 9:28:23 pm

Just to say after many many hours and sleepless nights, I've found the only possible solution I can come up with in the time I have.

That is to output my ProRes 444 timeline as 422 HDCAM SR. All the problems just vanish. Shame to lose all that info but fortunately the broadcast spec allows for 422.

No response from AJA yet but I'll be curious to know what they suggest.


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2017 CreativeCOW.net All Rights Reserved
[TOP]