forcing iframes

Former user wrote on 9/27/2007, 8:03 AM

I think I know the answer, but is there anyway to force an Iframe at a specific point in Vegas or MainConcept Mpegs?

I know DVDA4 will allow you to place an iframe, but it says it will re-render. Does that mean a full MPEG re-render, thus a quality hit?

Thanks for any help.

Dave T2

Comments

TheHappyFriar wrote on 9/27/2007, 8:07 AM

in vegas when you render you can specify how many i-frames a second (I assume that's what the i-frame thing means. someone know more?).

Former user wrote on 9/27/2007, 8:31 AM

thanks, I know you can determine the Iframe interval. I need to make specific frames an iframe for DVD chapter marks.

Dave T2

Chienworks wrote on 9/27/2007, 8:46 AM

The only way to move an iframe in an mpeg file is to regenerate all the pixels needed for that frame. That means re-rendering. Now, presumalbly a smart-render engine would only touch the GOP before and after the new iframe. I don't know if DVDA 4.5 has the new smart-rendering or not. If you really need to do this, i would render to DV .AVI in Vegas, then place the iframes in DVDA and have it render to MPEG2.

Former user wrote on 9/27/2007, 8:51 AM

Chienworks,

I have not used DVDA to create the MPEG. Have you? IF so, was the resulting quality equal to MainConcept?

Thanks.

Chienworks wrote on 9/27/2007, 10:34 AM

DVDA uses the same MainConcept encoder that Vegas uses. It doesn't offer as many options, but if you're not trying to cram 100+ minutes onto a disc the output should be just about the same.

Former user wrote on 9/27/2007, 10:51 AM

Thanks, Will give it a try.

Dave T2

farss wrote on 9/28/2007, 1:47 AM

If you're rendering from the Vegas T/L and place markers where you want the chapters you have a checkbox in the MC encoder to force I frames at markers.
Works quite well but not always.
DVDA will show you where the I frames are, I usually just nudge the chapter to line up with an I frame if it missed it for some reason.

Bob.

Former user wrote on 9/28/2007, 6:14 AM

I am using Vegas 6 and I looked for a force iframe to marker setting but could not find it. Can you tell me specifically where to look?

I know DVDA will show the iframes. What I am running into is I want to start the chapter in black, but the iframe is set a few frames into the fadeup. Causing the chapter to start abruptly.

Thanks for the tip.

Dave T2

farss wrote on 9/28/2007, 6:38 AM

Sorry,
this feature was added in V7.
How I used to get around it in V6 was just to have enough black so it didn't matter but that may not be possible in your case.

Bob.

Former user wrote on 9/28/2007, 7:14 AM

Bob,

Thanks. I thought I heard about that feature, but I guess it was when reviewing Version 7. I will try the DVDA route until I can upgrade to 8. I assume this is still a feature available in Version 8.

Dave T2

ScorpioProd wrote on 9/28/2007, 10:22 AM

Note that one of the main differences in encoding in DVDA versus in Vegas itself is that DVD A will NOT support 2-pass VBR encoding.

farss wrote on 9/28/2007, 1:23 PM

I don't know why anyone would encode in DVDA.
I haven't tested 4.5 extensively (from a quick check I think it's better) as yet but in prior versions anything such as menus that gets encoded in DVDA looks soft to me compared to encoding in Vegas. I am talking about PAL here though, maybe in NTSC things are different.

Bob.