Maxed out bitrates with 2.21:1 aspect ratio??!

entilza72 wrote on 12/13/2009, 1:31 AM

Hi gang,

I don't want to cross post or do anything close to that, but I would like to draw the collective wisdom to the attention of a post I made in the DVD Architect forum.

It concerns the curious issue of Vegas rendering a 2.21:1 ratio 9Mbps (or less) video-only mpg, but DVD Architect thinks its beyond its 9.917Mbps limit and forces a re-compress. It sort of sits between both products.

I seek guidance from the collective wisdom! :-)

Full details here:
http://www.sonycreativesoftware.com/forums/ShowMessage.asp?MessageID=685756
I'd appreciate it if discussion could be limited to that post, so we keep the knowledge in one place.

Cheers,
Jason

Comments

farss wrote on 12/13/2009, 4:07 AM

MPEG-2 encoders do overshoot, always leave some headroom. There's next to no difference between 8Mbps and 9Mbps. I always limit Max to 8Mbps as by the time audio is muxed in you are getting close to the point where some players will have problems keeping up.

2.21:1 is a wierd AR too. DVDs only support 4:3 and 16:9.

Bob.

TheHappyFriar wrote on 12/13/2009, 4:36 AM

2.21:1 is what 2001 was released in. For DVD/BD you just letterbox it. :D

entilza72 wrote on 12/13/2009, 5:43 AM

Hi guys,

Well, here's the thing...

1. Re: Letterboxing to a 16:9 frame - Vegas has, for at least since version 5, overlayed transition effects (and titles too, I think) OVER the top of automatic letterboxing (aka unticking "do not letterbox" in the render window). This means you see the transition effect over the top of the letter box - things like flashes, etc. Crazy, unusable stuff. So you have to fake a letterbox mask and superimpose a letterbox on a 16:9 project. Call it obsessivness, but I hate unnecessary keying/transparencies on a finish thats supposed to be the highest quality I can make.

But you are right, this would probably "fix" the issue.

2. Re: bitrates overshooting, I neglected to mention it does the same thing with a 3Mbps render. DVD Architect still says it's 9.917Mbps. There's no way its overshot that much. DVD Architect also says this is HIGHER than the max permitted, 10Mbps. Go figure!

I think this is a bug in DVD Architect, perhaps brought on by something not right in the MPG file from Vegas - a double whammy.

Cheers,
Jason.

entilza72 wrote on 12/18/2009, 5:32 AM

Hi,

Anyone else with thoughts on this problem?

I have now found I can achieve the same "bug" by simply changing the FPS in the MPG render settings. By dropping from 30 to 24, we get the same problem.

Simply: Set vegas at any variable or fixed bitrate (including stupidly low ones like 3) and Windows will report the correct bitrate, but DVD Architect will report a bitrate of 9.917Mbps everytime, saying that figure is higher than the allowed 10Mbps.

It then causes an unavoidable re-render in DVD Architect, overcompressing the image (which is the real issue).

Any ideas? I'm flummoxed!

Cheers,
Jason

TheHappyFriar wrote on 12/18/2009, 8:49 AM

I haven't played with the bitrate issue, but for the extra wide screen here's what I'd do: make your project & change the AR to the AR you want the output to be. Vegas will accept custom numbers. Then when you're done, render this out to a DVAVI, uncompressed, etc. Then bring that file in to a new Vegas project @ 16:9. Plop your video on the TL (should have black bars on top/bottom). Then render your mpeg-2's from that.

farss wrote on 12/18/2009, 12:56 PM

What is your MAXIMUM bitrate set to?
Set the Average to 3M and leave the Max at 9 and DVDA could well still see the bitrate as being too high. Some players only report the Average.

Bob.

entilza72 wrote on 12/18/2009, 3:08 PM

Hi Bob,

Max bitrate is as low as 3Mbps constant (not variable).

I have tried all sorts of combos with variable and constant. It all ends up the same - Windows reports the correct bitrate (in this case 3Mbps) whilst DVDA believes its 9.917.

The key seems to be: changing any of the frame rate or aspect options in the render settings seems to set this off.

If no one has seen this, I guess I'm dealing with the very percular bug that only appears under a specific scenario.

TheHappyFriar - thanks for the suggestion. That might help me get over the aspect ratio problem, but the same problem with frame rate has me flummoxed! I might try changing the project's frame rate instead of the render's frame rate.

Cheers,
Jason

farss wrote on 12/18/2009, 3:47 PM

"The key seems to be: changing any of the frame rate or aspect options in the render settings seems to set this off."

As I mentioned earlier the DVD spec only supports 4:3 and 16:9, although the encoder will do all manner of other things it's no great surprise that DVDA is not happy. It could well be that the error message telling you it needs to recompress the footage is giving the wrong reason why.
Certainly the DVD spec does not support 2.21:1 as an aspect ratio. That has to be letterboxed into 16:9 and encoded as such. I've done a little of this kind of trick and a heck of a lot of vanilla 16:9 DVDs and never had an issue.

Bob.

entilza72 wrote on 12/18/2009, 5:54 PM

Sorry Bob - my bad. I've not pointed out that I'm now getting the same results in 16:9 projects when I down convert to 24 fps.

Despite this missing info, I think you are right. The common thing in both the 2.21 problem and the 30fps->24fps problem is:

DVDA doesn't appear to support either of them.

Your comment about the DVDA doing only 16:9 or 4:3 is right of course, and I also noticed that DVDA does not give you the option of 24fps, only 25 and 29.97.

As you suggest - DVDA is probably encountering file specs it cannot work with, and is throwing the wrong error to do the right thing (that is, re-encode it to fix the problem). That's the most logical explanation for my mind.

In that light, it makes total sense.

Thanks Bob!

Jason.