Standard def render question

vicmilt wrote on 1/6/2010, 11:23 AM
Hi Guys -

I should know the answer to this - I used to!

Have been working in HiDef feature docs for a few years now, and suddenly am thrust back into the world of Standard def TV commercials.

Meanwhile, I've forgotten everything I know PLUS we've had a few upgrades, so all my prior setting are gone.

Q1 - I'm getting a bunch of horizontal lines on moving title renders for the finish. What settings should I be using? I know it's some interlace problem, but I do not remember actually being able to see these lines before (in full motion).
Q2 - Aside from the "Broadcast Color" filter - any other blivets to be watching out for?
Q3 - I'm going to be delivering spots to different stations in 1280x720 (HD) and 640x480 (SD) - any suggestions on workflow? And should I send 720x480 or 640x480 - the stations are asking for 640...

Advice cheerfully accepted and gratefully requested.

v

Comments

farss wrote on 1/6/2010, 3:39 PM
A1 - The problem you are seeing is Line Twitter. Interlaced video has a limit on vertical resolution of around 70% of full raster. Anymore and you may see exactly what you're seeing. It at one time was a real monkey on my back working with 1,000s of hires stills to be made into SD DVDs.

Best way to wrangle this I found was to use Vegas's Gaussian Blur FX and apply a tiny (0.001 to 0.003) amount in the vertical direction only. You need to eyeball the outcome on a SD CRT monitor. I would suggest applying the FX on the video bus master track, that way you catch everything but again eyeball the outcome.

A2 - That's a quite blunt tool. Make certain you adjust it to roll off rather than clip highlights, especially an issue if the footage came from a DSC based camera. They record in ComputerRGB, might also need to watch what happens with the blacks.

Other things to watch for are out of gamut colors. Again this depends on the camera. Video cameras are very unlikely to break the rules. DSCs might, don't know for certain. Only the most astute/caring broadcasters tend to reject content because of this. I know the BBC/ABC will. It will not break anything in their transmission chain but you might get a bit of shock when say a red product turns out brown. Need a vectorscope to check for this I think.

A3 - edit on a T/L that matches your source and render from that to your target. I'm not in NTSC land but I'd sure be sending them 720x480, that's the NTSC frame size.


Also watch out for aliasing problems. This really depends on the optics, the OLPF and the camera and what's in front of the camera. If you're shooting with a shallow DOF pretty unlikely to ever see it unless whatever is in sharp focus has lots of fine detail with sharp edges. If you ever do get this and it becomes a big issue for you then there are "anti-aliasing" filters you can put in front of the lens. Personally I suspect they're only something like a soft focus filter given a fancy name so they can charge more.

Bob.
randy-stewart wrote on 1/6/2010, 4:50 PM
Hello Victor,
Wow, Bob covered all of your questions much better than I can. Thought I'd add a tip about lighting...don't forget to Light It Right. Recommend you use this really cool light called the Milt Nanolight. You can make it yourself! And it's portable so you can take it everywhere...wait a minute, your THAT Victor, aren't you...never mind.
:-)
P.S. Hope to see you at NAB this year.
vicmilt wrote on 1/7/2010, 4:15 PM
Thanks for the kind words - and Bob thanks for your in-depth discussion...
but -
I probably did not make myself clear about the issue.

It's not that I have thin horizontal lines in the graphic.

It's easier and harder.
The thin lines I'm talking about are like "field lines" or interlace lines.
There must be a setting in the render as settings that will address these lines.

For instance - I'm using the standard type tool (has anyone figured out how to work the ProType tool?) and I've got some large words dropping down the middle of the screen at a high rate. Well - even in playback you can see the field lines. I don't remember having this issue before. But I did the same type of graphic a million times. But that was on BetaSP.

I haven't seen them before - in a freeze frame they are clearly evident in any motion image. In the actual playback they are not so evident - but they definietly are there. Perhaps I've simply gotten so used to seeing HiDef progressive footage that what was once invisible has now become hugely apparent.

Or (what I'm hoping) - there is a button to be pressed.

v
I
farss wrote on 1/7/2010, 6:09 PM
"It's not that I have thin horizontal lines in the graphic"

Understood.
The problem is much the same if it's a line or an edge.
The edge can be positioned such that it's only in one field, hence it flickers, It's there in one field, gone the next then it's back again.

Vegas does have a Reduce Interlace Flicker switch however it's rather blunt and will make everything soft. My previous suggestion of using Gaussian Blur should fix the problem for you. That will soften the edge so it spans both fields.

NewBlue also have an antialiasing plugin that could help you as well. It should help with diagonals on text if you're getting a problem with 'staircasing'. I haven't actually tried it myself however considering that Vegas doesn't wrangle the aliasing problem all that well it could be a vital plugin to have.

Bob.
BudWzr wrote on 1/7/2010, 7:21 PM
Bump up the project frame rate to 60, or slow down the motion. If it's on a prerender, render again at a higher bitrate. Make sure you select "blend" for any de-interlace option.

I just had this exact same issue. It's a "comb" pattern on the text only right?

NOTE: Please don't blast me anyone. It's just dumb luck that I just went through this myself.
Coursedesign wrote on 1/7/2010, 7:39 PM
1. And should I send 720x480 or 640x480 - the stations are asking for 640...

720x480 would be NTSC 0.9091 PAR (Pixel Aspect Ratio) pixels, 640x480 would be square pixels as used for computer video.

2. For the horizontal line problem, when your project is interlaced, you can only use certain rates for vertical scrolling. Only even multiples look OK, so use 120 scanlines/sec, or 240, 360, etc. for NTSC (or 100, 200, 300 etc. for PAL).