AC3 Strangeness

Rain Mooder wrote on 3/22/2003, 12:11 PM
Feature/Bug:

Another problem, sometimes I render AC3 files and it takes 8 hours to
render. These AC3 files are duds and never yield any sound. Other times
they take 10 minutes to render and work fine. I'm rendering 2/0 stereo
clips from the 1:19:39.21 long files. Here's what I've noted,
- If I don't touch the preset the render happens in 10 minutes/works fine
- If I change the dialog normalization from -27db to -29db I get 8 hour renders and no sound plays anywhere
- If I change the bitrate from 192kbps to 128 kbps and click through the warning I get 8 hour renders and no sound plays anywhere
- If I shift the bitrate from 192 to 224 it also renders for 8 hours and doesn't work

It seems that any change to the AC3 preset causes the render to be spoiled.

Comments

Spot|DSE wrote on 3/22/2003, 5:00 PM
There are specific combinations that work for altering AC3 files. It's not like you can just "oh, I think I'll change this" and expect it to work. AC3 is very specific about structure. 8 hours to render an AC3 that is 1:19:00:00 long? It's more than just the AC3 happening there. You are rendering something else, or something on your system is interfering with the render. I'm changing the dialog register often, to pop the center channel, doesn't seem to be taking any more or less time. That's an odd one. Do you have other AC3 authoring tools? Any other apps that read/resolve AC3 files?
Rain Mooder wrote on 3/22/2003, 6:55 PM
>There are specific combinations that work for altering AC3 files. It's not like you >can just "oh, I think I'll change this" and expect it to work.

Ahh. If this is true it would be very nice if Vegas would pop up a box
saying "This is not possible." I am surprised, however, that one cannot
adjust the dialog normalization down two dB without causing strange
behavior

> AC3 is very specific about structure. 8 hours to render an AC3 that is 1:19:00:00 >long? It's more than just the AC3 happening there. You are rendering something >else, or something on your system is interfering with the render.

I have no other programs rendering and I have no programs related to AC3 other than DVDA and Vegas. I can test the standard AC3 stereo, see that it works, then immediately try with a modified AC3 parameter and have the render go funny. I can then cancel out of that and try the standard AC3 template and see that it works. There is nothing other than the parameter in the AC3 setup changed. I have done this at least 4 times under the most controlled circumstances I can manage under XP with
the same result. It is perfectly repeatable.

>I'm changing the dialog register often, to pop the center channel, doesn't seem to >be taking any more or less time. That's an odd one. Do you have other AC3 authoring >tools? Any other apps that read/resolve AC3 files?

I'm not doing 5.1, just 2/0. That might be the ticket. Shame to waste all those bits, though.
Spot|DSE wrote on 3/22/2003, 11:33 PM
Send me a veg, will ya?
dse@sundancemediagroup.com
pcfreakx wrote on 3/23/2003, 2:07 AM
Guys, I got the same thing. My audio was a bit low so I tried to change the dialogue normalization to boost the level and that renders either a blank sound, or a binary type file - just weird beeping; like the ac3 isn't being decoded. But here is the kicker. If I leave all other settings exactly the same, and all I do is change the dialogue normalization, I get this same freakiness. Definitely a bug going on here. I have softencode and I will try to play with that instead.
Rain Mooder wrote on 3/23/2003, 12:37 PM
I reinstalled Vegas+DVDA. I did the following after install,
1. Render with "Stereo DVD" template, no mods
...Worked
2. Render with "Stereo DVD" template, bitrate set to 96kpbs
...Worked
3. Render with "Stereo DVD" template, bitrate set to 96kbps, dialog set to -29db
...Failed
4. Render with "Stereo DVD" template, bitrate set to 96kbps
...FAILED ?

DSE couldn't reproduce the problems I'm having.
I think it broke itself on render 3.
Spot|DSE wrote on 3/23/2003, 1:52 PM
If I change nothing but dialog and bitrate, I get a successful encode. If I mess with anything else, it breaks. I'm certain you are right, seems to be a bug in here, because while I can't repro from your project, I can repro part of the problem. SOFO is aware of the issue.
SonyDennis wrote on 3/24/2003, 9:30 PM
There is a known bug (fixed in the forthcoming 4.0b update) that will have the "Stereo DVD" template making 5.1 files. The work-around (until 4.0b is out) is to select the Stereo template, hit "Custom", add "workaround" to the name, hit "Save" and then use that template from than on. Perhaps that same bug is causing these long render times and bogus output, I don't know.
///d@
minstrel142 wrote on 3/25/2003, 8:38 AM
I've tried the "workaround" bugfix and it cures the Stereo template problem, but not the other strangeness, which I am also experiencing. If I use the Custom page to change Dialog Normalization levels (or any other parameter, it seems) then an empty file and a very long render time to get it is the only result. SoFo Please help!
Sunray wrote on 3/25/2003, 2:11 PM
We've tracked down and fixed the "empty" or "noisy" render bug as well. This should be available in the upcoming Vegas 4.0b release.

-pj
minstrel142 wrote on 3/26/2003, 3:36 PM
Excellent!