DG System Back Level

[Craig Seeman]

Are you delivering to a specific station or to several stations but only one is showing this issue?

You state poor results at “some” stations. Have you been able to view the same spot airing at two different stations.

If one station is good and the other isn’t then I’d believe the issue is “station side.”

I’ve delivered 0 black to DropBox and seen spots play on two stations and they looked identical (booth good) . . . this even though their specs say that you should add 7.5 black on your end. I may have raised black a smidgen (technical measurement of course) above 0 thinking that might “trigger” something.

[Craig Seeman]

BTW, I believe DG has changed color space from 4:2:0 to 4:2:2 as part of their spec. That shouldn’t cause the issue you’re seeing though.

BTW you can try checking encodes in VLC086c also. No scopes of course but it’s good for an eyeball QC.

[Fred Connors jr.]

Thanks for the feedback Craig.

We have found the problem. And yes we are sending to 50 stations regularly. And yes we have seen the problem on all local stations.

All of DG’s playback systems default to add Setup to the Composite output of their video card. Composite Setup On also adds 7.5 IRE of black to the SDI and/or Component outputs. DG will not acknowledge this but the supplier of the video output card has acknowledged it.

This is why things look bad.

We now use a proc-amp filter adjusting the Setup down, Video Level Down and Chroma Up to compensate for the 7.5 of back being added on output of the video card.

Fred

The Troupe – Modern Media Design & Production

[Craig Seeman]

It’s interesting how DG says you should add 7.5 black on the content creation side. I’ve done near 0 (working in DVCAM for local cable spots) and they don’t seem to have issues and my spots looked good.

[Anthony Miles]

Fred, Craid, Great thread, Thank you!
Please help me avoid the same problem. Fred, is your footage coming in from analog source with setup already added?? I ask, as most digital sources usually have 0 IRE setup. Mine are digital, HD with 0 IRE black into an FCP sequence at 8 bit uncompressed 23.976. I am outputting this file as 8 bit uncompressed and nesting the file into an NTSC 8 bit timeline at 29.97. My blacks stay at 0 IRE for this, I am also adding Proc Amp filter (to bump blacks to 7.5) as DG asked for 7.5 blacks, which I usually never put on digital files for digital delivery as I know most devices add setup on analog output. They also asked for upper feild first in their mpeg files. Is ths right, I thought most systems use lower feild first for NTSC, my old Digisuite used upper first, I think???

Any how these spots are going to a remote market that I will never be able to see to spot check. If you could summarize the best practices for DG DropBox, based on your experience that would be a tremendous help. Best/recommended software for this encoding job??

Best regards,
Anthnoy Miles
Intel Mac, FCP6 Still on Tiger, Decklink HD extreme

[Craig Seeman]

My sources are digital too. Usually DVCAM although I’m moving to XDCAM in the near future.

MPEG2 Program streams are usually upper field first so I just switch that in my Episode template for DG and it works. DG will contact you if they see an issue. They’ll go through a testing procedure (upload 5 good test spots) before they let you start using the system.

The odd thing when I started testing with Pathfire with MPEG2 Transport streams (owned by DG now) they spotted the field switch “judder” and told me it was OK to keep it lower field first.

For black I just cheat my digital source up to the equivalent of 1 IRE (thinking 0 might trigger something on their side) and it passed through. My spots looked good so I’ve stuck with that setting.

[Anthony Miles]

Craig,
Thank you very much. How about the 720×512 frame size. That is a bit mysterious to me. Any clue to what that odd frame size is related to and if I need to set it to that. Do you take a standard 720×486 or 480 file and set it in the encoder for 720×512 to resize??? Siimilar to changing the feild order? Any trick to that?

Thanks again,
Anthony Miles

[Craig Seeman]

MPEG2 is normaly 720×480. In my template I have setting that crops 720×486 to that size.

720×512 is a setting that Pathfire uses. You “crop out” sort of like creating black letter box during encoding. You’re not resizing the video image at all. That creates space in the verticle interval for Sigma encoding for VNR use tracking. You don’t need to do that for TV spot distribution since you just need proof/certifcation that they aired.

It’s important to note that for broadcast you’re not changing pixel aspect ratio either (compared to changing not square to square for computer/web use).

[Anthony Miles]

Thank you Craig.

[Fred Connors jr.]

Anthony

If you Proc the video to 7.5IRE your black level will be at 15 IRE when it hits the air.

We produce everything with digital 0 black.

You can not compensate for the DG added black with just lowering your black level, or as they said in he old days “Crushing the Blacks”.

We found we had to adjust three levels with the FinalCut Proc filter to compensate.
Setup = -0.25, Video = -0.38 and Chroma = +1.05

It is not perfect, but it is much better than no compensating.

Fred

The Troupe – Modern Media Design & Production