Subject:AC-3 Questions

Posted by: Mr_Plant

Date:3/31/2003 11:05:22 AM

My Purchased version of Vegas+DVD arrived today!!! wohoo!!!!
I have a question about AC-3 audio.
I have cleaned up the audio to sound great on the DV master. (from a VHS source through my Canopus DVC-100 unit).
I have converted the video/audio to MPEG using the MainConcept encoder.
ULEAD DVD Moviefactory 2 will burn the resulting file with MPEG audio just fine and it plays brilliantly on my dvd player.
I know that MPEG audio is not really the DVD spec but I live in a PAL area where it is.. Anyway MovieFactory burns it and it plays. Sound is great.

Now my questions..

1/. I realise that DVD Architect does not allow MPEG audio and wants always to re-encode it. Could someone from SonicFoundry let us know if they are working on a future update that will allow it to burn MPEG audio as it stands without a re-encode (perhaps with a 'non-standard PAL MPEG Audio' tickbox??). Is this feature likely to be ever available? I, and lots of others, I am sure through reading through these forums would appreciate this feature!!

2/. I did a seperate AC-3 sound render to keep DVD Architect happy and imported it and burned it. The resulting sound was 'worse' than my original mpeg version.
The sound was mainly lower. I notice there are lots of settings in the AC-3 codec.
My source is a stereo format file only.
What are the best settings to use that will ensure that the level of the audio in the AC-3 file will stay at the level I mastered it at?

(I just noticed the AC-3 forum here - I have posted similair in the Video forum)
Thanks for reading.
P.S. - I really appreciate these forums - a great resource to everyone!!

Subject:RE: AC-3 Questions

Reply by: rphtx

Date:4/11/2003 7:53:38 AM

With the number of posts concerning the AC-3 rendering process messing up the sound levels, etc...you would think one of the SoFO guys would have posted by now. This question appears across 4 or 5 forums with multiple posts on each and there has been no answer. Maybe someone needs to contact them directly??
I'm in the same boat if it makes you feel any better :)

Subject:RE: AC-3 Questions

Reply by: Mr_Plant

Date:4/12/2003 11:23:32 PM

Hi!
I did mail SOFO directly and about a week later got a reply. It wasn't any use to be honest - said to check the AC-3 options for different settings and that was that. No technical details. I've tried test renders messing about with the settings and I can't get the audio any louder... All I am asking for is a setting that leaves the audio level the same as the level on the input to the encoder - without dropping it...

Subject:RE: AC-3 Questions

Reply by: rphtx

Date:4/14/2003 4:29:17 PM

The lack of any official response indicates they know about it and it is definately
a bug. Hopefully it is addressed in a patch soon, because both programs are useless (except for editing on the computer) for burning any DVD's at this point.

Subject:RE: AC-3 Questions

Reply by: Baylo

Date:4/15/2003 2:18:16 PM

"The lack of any official response indicates they know about it and it is definately
a bug"

Now that's what I call jumping to conclusions! I think you have SoFo confused with some other software developers...

You might be right. I don't know. My experience here in the past has been that SoFo have confirmed bugs on the forum when they have been able to replicate. If nothing else, it gives people an answer as to why something doesn't work as expected and keeps the noise level down. The fact that they haven't, suggests to me that it isn't a bug. However I do concede that it's odd they haven't responded to any of these threads.

Mark

Subject:RE: AC-3 Questions

Reply by: radcamdvd

Date:4/17/2003 9:47:52 AM

I have to say that I'm disappointed with the AC-3 tool that Sonic Foundry has deployed with VV4 and VV4+DVD.

Sometimes a client will give you an AC-3 file and ask if you can modify a track or two. For example, if the narration is over the center track, they may ask for modifications or updates that they provide separately. The AC-3 tool is useless for this task.

The thing is that Sonic Foundry's Soft Encode was able to deal with this situation. In fact, Soft Encode would allow for 5.1 to 2.0 downmixing. The AC-3 plug-in will not import AC-3 files to do anything.

I didn't appreciate Sonic Foundry's response to me personally on the phone that because they make programs available for trial use it's up to users to test them first. Why would anyone expect that they would decrease functions with a new release? But more importantly, AC-3 is not available in the trial versions.

VV4 AC-3 plug-in is one example of the flaw in their logic. If all they wanted to provide was an AC-3 encoder only (and defeat the decoding ability) then they should have added the function to DVDA alone. Then no one would have been mistaken in thinking they were buying an encoder that could decode as well. It doesn't and we suffer as a result.

I am dissatisfied with this and would have bought their products at all if I'd have known. I'd have rather spent the money, even if it was expensive, on a solution that worked. Unfortunately, Sonic Foundry isn't interested in returning my money so I'm stuck with a bitter taste in my mouth about Sonic Foundry. I may just be the tip of the iceberg. The product is so new, who knows, and who cares. I've wasted $500 for something that doesn't work and I'm not interested in products that are only partially fictional. Who has the time to piece apps together instead of doing the work?

Subject:RE: AC-3 Questions

Reply by: dvddude

Date:4/17/2003 4:04:11 PM

I'm having issues with the AC3 encoder myself, but honestly, I would never have expected it to be able to go in and re-edit AC3 files. After all, it's an "encoder." Dolby Digital is an EXTREMELY lossy format, and used for final product, not for continuous rediting.

By comparison, I paid $500 for Ulead's DVD Workshop because it had AC3 capability only to find out that it didn't even have an encoder! Never mind a decoder. Now that's a bummer.

Subject:RE: AC-3 Questions

Reply by: Sunray

Date:4/18/2003 2:05:20 PM

I'll address your 2nd question:

As has been noted many times on this forum, there can definitely be a drop in levels after encoding to .ac3. This drop has everything to do with you source material in combination with the AC3 encoder settings. I'd recommend modifying the dynamic range compression method (in the Preprocessing tab) as appropriate for you source material. I'd also tweak your dialog normalization level. The lower the value, the higher the gain when your encoded material is decoded.

As I suggested on another post, check out the following information from Dolby:
http://www.dolby.com/tech/L.mn.0002.DDPEG1.pdf

-pj

Subject:RE: AC-3 Questions

Reply by: Mr_Plant

Date:4/21/2003 7:06:08 PM

Thanks everyone. Good to get some feedback from people on this - Checking out the recommendations!

Subject:RE: AC-3 Questions

Reply by: dvddude

Date:6/5/2003 2:49:11 PM

The worst thing SoFo did regarding the AC-3 encoder was to default the dialog normalization to the setting they did. A quick scan of this forum shows that the confusion caused by the low volume levels is nearly universal. It seems to me that they could sidestep a lot of AC-3 support issues if they either beef up the docs, or else deafult that diaog normalization level to -31. It seems that this almost always does the trick, but every poor soul that buys the program has to go through days of hair-pulling and forum-surfing to get this answer. I don't understand the decision to default that setting to one which would cause such grief in 99% of the projects out there.