Vegas 7.0b and DV Files - Unreliable Preview?

Stuart Robinson wrote on 10/16/2006, 11:28 PM
I'm noticing something strange about the way Vegas is displaying DV files.

I just recently started capturing some material with a Canopus ADVC110 and am battling an issue with video noise (the type that looks a bit like dot crawl) with some sources.

However, this issue really only came to light when I took a look at the source files in VirtualDub. There, the noise is quite evident at 100% display size, whereas in Vegas the footage looks almost completely clean. I'm wondering what's going on, is the Vegas preview soft or is there some NR in the chain?

I've looked at the footage in VirtualDub on two machines, one using the MainConcept DV CODEC, the other the Panasonic DV CODEC. It's pretty much the same on both. Noisy.

Vegas is using its own CODEC (with ignore third-party CODECs checked) but the output is still cleaner when it's set to use the Microsoft DV CODEC. In Vegas I'm using the best preview quality (set to full), and there's no conversion to progressive in the properties, it's just straight lower field first.

I've got to admit to being a bit troubled by this, if Vegas is somehow hiding or masking video noise that's quite evident in VirtualDub, it makes me wonder what else I've been missing.

Any ideas would be appreciated - I can post frame captures if it helps the resident experts!

Comments

Marco. wrote on 10/17/2006, 12:55 AM
Be aware if using Panasonic DV or if havn't MainConcept DV properly adjusted those codecs do stretch the lumanince range when decoding. This can pump up the noise. The dv codec inside Vegas does handle the luminance range 1:1 and this way noise stays where it is.

So DV preview in Vegas is reliable. DV preview in VirtualDub isn't, dependend on the codec used for decoding.

Marco
malowz wrote on 10/17/2006, 12:56 AM
i did a little test comparing codecs some time ago, and vegas was for sure the "less modifiyng" codec over compression/recompression.

it does not modificate, mask, adjust in any way, it keep original as possible.

try to open the file via avisynth > virtualdub.

the levels may differ, so u can get a darker/more contrast image in vdub.

this may be what causing this difference.

also u can save images from vegas / vdub and compare based in these images, not in the preview window of virtualdub.

but with no doubth, vegas is the best codec and not modify the image in any way... because i test it ;)
Stuart Robinson wrote on 10/17/2006, 10:03 AM
Thanks for the replies. The Panasonic DV CODEC doesn't have any adjustable parameters, I'm not sure about the MainConcept one but I'll check it later.

There are some subtle differences in levels and the VirtualDub display does tend to have more contrast, but I'm not sure that fully explains the large differences in apparent noise between the two, it seems to be too aggressive in VirtualDub to be a result of a small contrast tweak.

Will investigate further and post some screen shots later...
John_Cline wrote on 10/17/2006, 11:18 AM
Stuart,

Are you running the Vegas preview at the full 720x480 or do you have it set for some smaller window size? Also, do you have it set for "preview - auto" or "best-full"?

John
Marco. wrote on 10/17/2006, 11:47 AM
>> The Panasonic DV CODEC doesn't have any adjustable parameters

Right. This is the reason Panasonic DV always expands the luma range when decoding. No way out.

>> I'm not sure about the MainConcept

The adjustments to MainConcept DV can be done via the Windows system control. Check the tab where all the Windows installed codecs are listed and check the properties of MainConcept DV there. You can select whether using RGB 0-255 or 16-235.

Marco
riredale wrote on 10/17/2006, 1:12 PM
If you ever use the MainConcept DV codec for anything, make sure that in the MainConcept configuration screen, the "fast encoding" checkbox is turned off. Makes a huge difference in artifacts.