Black levels revisited

zipwax wrote on 11/10/2003, 5:51 PM
nobody knew what the answer was to black levels. so I did a LOT of testing. You can have fun with the results. I have 3 DV encoders on my system: the MS one, the one that shows up in Vegas (you can't even select the MS one from Vegas), and I have the MainConcept DV codec installed. The MainConcept encoder has a checkbox on it that cryptically says, "RGB16-235" with no help.

here's the results:
1. If you encode to DV using the default encoder, then try to decode in any application BUT vegas, you'll get crushed toe/head room.

2. if you encode to DV NOT using the default encoder, for example MainConcepts, then unless you have the MainConcept's RGB16-235 button checked on, when you reimport it into Vegas, the black levels will all be off because Vegas expects it's special DV encoder.

3. If you don't want #2 to happen when encoding using other encoders, uncheck the "ignore 3rd party codecs" in Vegas and possibly (or not) check Use MS's.

4. Basically, MainConcept's DV encoder and decoders act EXACTLY like the default Vegas codecs if and only if you check RGB16-235 on BOTH of them.

I'm not sure what the difference is between using Vegas' RGB16-235 codec all the time for production work, or using some other codec the whole import and export process.

Sheesh.

Comments

Spot|DSE wrote on 11/10/2003, 6:02 PM
RGB 16/235 isn't a codec, it's a color filter. 16 is the digital equivalent of setup, or 7.5 IRE. 235 is the legal max for bright, or matches 100 IRE.
Do a search on legal colors, John Cline did an excellent post here on this, or there is a section in the Color Correction chapter of my book that explains this.
Restore Black Levels isn't really for setup, the Broadcast Clamp would be a better choice in most instances.
Although you can use Black Restore for broadcast signal, it's also a very useful tool for any deep compression such as streaming or MPEG. It reduces the gradients of black that the eye can't really see but the encoder sure can, and reacts to.
You can access the Microsoft DV codec in Vegas should you wish to, but I'm not sure why you'd want to.
zipwax wrote on 11/10/2003, 7:25 PM
I didn't say RGB 16/235 was a codec. It's an OPTION on the MainConcept DV encoder. Have you USED Vegas and the MainConcept DV encoder?

:-)
taliesin wrote on 11/10/2003, 8:09 PM
But you wrote "Vegas' RGB16-235 codec".
What did you mean? There is no such a Vegas codec. Vegas does NOT reduce color space to 16-235 unless you tell Vegas doing this by using a certain filter.

Difference between Vegas DV-codec and some others is: Vegas handels full range of RGB 0-255 (except Avid, CanopusDV which does same and the latest MainConcept version) and - Vegas DV-codec (or should I say "Sony Pictures DV codec") has very little render artifacts. Much less than Microsoft for example. And - Sony Pictures DV codec it free for us Vegas users ... ;-)
I can't see any reason NOT to use Sony Pictures DV codec when working in Vegas. I tested some DV codecs but none were better then Sony Pictures DV.

Marco
farss wrote on 11/10/2003, 8:32 PM
taliesin is right, the VV codec will encode the whole 0-255 range i.e. generate illegal levels if you don't stop it. 7.5 IRE is a separate issue.
The Broadcast Colors fx lets you apply the setup if you need it.
I cannot say what other encoders do, I've never found any reason to stray from the straight and narrow.
Spot|DSE wrote on 11/10/2003, 10:32 PM
Yes, I've used the Main Concept codec, and the Vegas/Sony codec, and just about every other codec under the sun. In fact, I'm the person who not only did the original codec testing, I'm the guy that screamed bloody hell about codecs to the point of taking a machine to Madison, Wisconsin to share my findings and opinions with the Sonic Foundry engineers. And not long after, Bob G. and the gang there did a bang up job creating their own codec rather than relying on M$DV's horrible MS7 codec.
Look on our website, you'll find the original codec tests between most major codecs of 2 years ago, comparing Sony codecs, their derivatives, and the MS codecs at the time.
Codecs are one of the most confusing issues for folks to understand, as the file type can be an avi, but contain any number of codecs in the avi wrapper.
Vegas' codec behaves just like MS, and other codecs that don't account for setups and color legality. It's part of RGB. Computers 'need' no setup or legal colors, and therefore, since the NLE's author for computer-based video, export back out to tape isn't actually a primary focus. Also, many cameras capture outside of legal colors, and to have a codec that auto-cuts anything below 16 RGB/7.5 IRE, and anything above 235RGB/100IRE, would automatically screw with what the camera output. Most of us wouldn't like that. Especially those in PAL land, because color issues aren't as great there.
All that said, the reason I assumed you were confusing codecs was your last line, "I'm not sure what the difference is between using Vegas' RGB16-235 codec all the time for production work, or using some other codec the whole import and export process. My apologies for misunderstanding.
Glad to know you haven't confused codecs, but if you use the Main Concept, Huffy, or any other codec other than the Sony/Vegas codec, you lose quality. Canopus and Vegas' codecs held up best in render tests of more than 25 renders of test media. The colorspace/render test is still available on the Sundance site if you'd like to check our results.