Banding in HD generated media from 6.0b

jlafferty wrote on 7/3/2005, 8:11 AM
Hey...

I'm trying to create a smooth gradient in Vegas, on a diagonal, from grey to black. I'm outputting it to 1280x720 and in both the preview window (best, full) and the generated media, I'm seeing distinct separation of the grey values as a series of diagonal bands. I'm outputting this to a signpost and compressing it with Nero for the h.264 codec. I haven't tried another codec yet because ultimately, the client requested h.264 (this material will be going into FCP).

The material is progressive, and I'm viewing it on a progressive LCD screen at 1280x1024.

I've tried a gaussian blur on the background, but that does little to change the issue -- all it does is change the shape and/or position of the banding.

Any advice?

- jim

Comments

Spot|DSE wrote on 7/3/2005, 8:35 AM
Banding in MPEG compression of gradients is common. Try crushing the blacks a little more, use the Black Restore plug as a "try" and do the same with levels.
To use .264, you'll likely need a much higher bitrate to make this go away.
jlafferty wrote on 7/3/2005, 8:51 AM
Thanks for the response. I've since been experimenting with a few things. I simply can't get a good looking gradient from Vegas, so I'm saving a 150dpi gradient PNG from Photoshop and laying that down as the background. The banding is present but very supressed relative to Vegas's Generated Media. I wonder if I'm missing a setting in Vegas possibly -- I've got my Properties set correctly, and have checked the Properties of each of the generated media...everything looks good from the numbers, it just shows up terribly in both the preview and output.

Outputting to HuffYUV things look great. High res QT files haven't worked out well just yet, but I'll keep trying -- any advice on what codec to use? I accidentally went unconstrained 32bpp and a 5 second render weighed in at 1.02gb!

Thanks as always,

- jim

p.s. All the h264 stuff I'm putting out is at 16.00mbps.
Spot|DSE wrote on 7/3/2005, 9:59 AM
Are you looking at this on a plasma monitor? Even though it's HD, I'm downsampling to SD and zooming in. Not seeing banding.
If you're viewing on an LCD or Plasma monitor, banding can sometimes/often be seen even though it's not really part of the media. test this on a CRT for certainty.
jlafferty wrote on 7/3/2005, 10:17 AM
Guess I should've kept one of my CRT's then, eh? :D

Alright, I'll check this stuff at the studio later in the week on their monitors. As a general rule of thumb -- when going from Vegas HD to FCP HD, what format do you recommend? Obviously QT would be a choice, but set to what? I've been doing some very high res QT 6.5 renders: sorenson 3, high quality, target rate 1024kbytes/sec, 24bpp. Is there something better (other than uncompressed)?

Thanks, again.

- jim
Spot|DSE wrote on 7/3/2005, 10:31 AM
The 4:2:2; YUV is your best option, but you could output sequential tga...Ain't no easy/fast way to do this.
B_JM wrote on 7/3/2005, 10:50 AM
you can use QT Targa also ....

sorenson 3 will cause banding as will viewing on a LCD screen as mentioned ..

jlafferty wrote on 7/3/2005, 11:37 AM
Thank you both. I'll try the TARGA option out and load a bunch of these on CD and check them out on the plasma.
jlafferty wrote on 7/3/2005, 11:49 AM
One, possibly last, question -- what do you guys view your YUV material in? I'm getting a black screen in both WMP10 and MPClassic.
Spot|DSE wrote on 7/3/2005, 11:52 AM
I view it out over SDI to my monitor, from Vegas. But you should be able to see it in your Classic player. I don't have YUV footage on this laptop, or I'd be happy to check it for you.
jlafferty wrote on 7/3/2005, 11:57 AM
OK. I'll keep trying. The TGA sequence looks great, shame it's about 90mb/sec =:O
B_JM wrote on 7/3/2005, 3:57 PM
Use compressed targas (lossless) , not uncompressed targas ...

dont export targas out of vegas directly ever as it is way to slow ..

frameserve to virtualdubmod and save targas that way...

if you already have all your targas, you can compress them in-mass with XNVIEW or IRFANVIEW which willsave you a lot of room ..

also - you can render out to QT using the targa wrapper, which some people prefer when using in FCP
jlafferty wrote on 7/3/2005, 10:23 PM
OK -- now that you've opened that can of worms:

Saving TGAs in VDubMod -- I don't see the option. What codec am I missing?

Render out to QT using the TGA wrapper -- was I doing that before? I was selecting QT .mov as my output in Vegas, and from within the QT template, selecting TGAs. Quality slider has no effect on the size of the output file :/

Thanks!

- jim
jlafferty wrote on 7/4/2005, 10:19 AM
Google to the rescue. I now see how to export TGAs from VDubMod, but I'm unsure whether or not these are compressed/lossless like you suggest (haven't actually done it yet to see the directory's size). I'm holding off on doing this until I understand how to properly re-assemble the image sequence into a QT .mov without significant quality loss. I expect and upgrade to QTPro 7 is in order as my Pro license has now expired?

Thanks,

- jim
B_JM wrote on 7/4/2005, 10:22 AM
you dont need any codec in vdubmod, just file -> "save image sequence"

you have the choice of png, bmp or targa


As for the QT Targa output, i wasnt sure which way you were doing it - as you can save a image seq. directly out of vegas also using a script..

John_Cline wrote on 7/4/2005, 10:38 AM
Jim,

You might want to add a little bit of noise to the gradient background to "dither" it. This will most likely eliminate the banding.

John
jlafferty wrote on 7/4/2005, 10:52 AM
Alright, I'm a little confused now. Sorry.

Workflow is as follows -- Vegas Generated Media --> TGA image sequence within a .mov file. This is what's getting me 90mb/sec.

I thought maybe you had advice on how to get the workflow so that it would go from Vegas --> VDubMod --> TGA quicktime wrapper at a smaller file size (compressed but lossless as you suggested).

If it is what it is, and I have to live with the filesize, I'll do it. I was just hoping I could go from Vegas to, say, data DVD with 3-4 sample videos at 30 seconds each. At this rate, I'll be able to fit only two videos on a typical single layer DVD (if that).

Where I'm confused is: are TGA's from Vegas already compressed/lossless? Will exporting TGA's from Vegas, via VDubMod, allow me to then recompress them within a QT wrapper at a smaller filesize (without significant quality loss)? And if so, do I need to have QTPro or some other tool installed to do so?

John -- thanks for the idea -- I'd been attempting gaussian blur on that layer in hopes of creating the same solution.

Thanks, again.

- jim
jlafferty wrote on 7/5/2005, 8:50 AM
*bump* Holding out for some clarifications, still... thanks,

- jim
B_JM wrote on 7/5/2005, 2:49 PM
Vegas --> VDubMod --> TGA , compress with xnview or irfanview to TGA compressed (LZW lossless compression) ...

or if you need smaller file sizes - jpeg at 100% quality ...

do you really need Quicktime ?

if so - there are a lot of QT choices
jlafferty wrote on 7/5/2005, 10:04 PM
Well, it's going to be intercut with Varicam stuff inside of FCP (haven't gotten the chance to make the Vegas pitch, yet :)

So, yeah, I guess/think QT will ultimately be easiest. Thanks for your info above -- I'm eager to look into your suggestions.

- jim