Subject:AC-3 stereo volume too low workaround

Posted by: way2slo

Date:4/19/2003 2:09:22 AM

solution:
under dolby digital AC-3 template > preprocessing > dynamic range compression, i set both line mode profile and RF mode profile to 'none', they are set 'film standard' by default. change the dialog normalization to the lowest -31db. i render an AC-3 stereo again, now the output level is the same as preview. looks like the file has been compressed there.
btw, what is line mode and RF mode? what do they do?
thanks

Subject:RE: AC-3 stereo volume too low workaround

Reply by: MarkWWW

Date:4/19/2003 9:43:01 AM

Dialog normalization level and the Line mode and RF mode Dynamic Range Compression values are some of the items of Metadata that are included along with the audio data in the AC-3 stream. In effect they tell the decoder how to modify the audio as it is decoded, applying level shift (in the case of DialNorm) and choosing particular dynamic range compression characteristics (in the case of Line/RF mode DRC).

In order to understand how metadata works (and hence how to achieve what you want when using AC-3 audio) it would be a good idea to have a look at Dolby's published information on the subject. Sunray has referred to one of these: "Dolby Digital Professional Encoding Guidelines" (http://www.dolby.com/tech/L.mn.0002.DDPEG1.pdf) and similar information can also be found in a more simplified form in a couple of other publications, "All About Audio Metadata" (http://www.dolby.com/metadata/pa.in.0101.AllMetadata.pdf) and "Dolby Metadata Guide" (http://www.dolby.com/metadata/pa.st.0102.MDGuide.pdf)

Subject:RE: AC-3 stereo volume too low workaround

Reply by: way2slo

Date:4/20/2003 6:26:03 PM

another problem here. i preview the ac-3 in DVD-A, volume is ok now but i do get pops noise randomly. again render the same file as pcm 16bit 441, not problem.
any idea?
thanks

Subject:RE: AC-3 stereo volume too low workaround

Reply by: way2slo

Date:4/22/2003 12:38:34 PM

bump :)

Subject:RE: AC-3 stereo volume too low workaround

Reply by: SonyEPM

Date:4/22/2003 2:09:21 PM

We'll be revving the AC-3 decoder in the next update, hopefully reducing if not eliminating the clicking in DVDA previews of AC-3. This doesn't show up in the render- just DVDA preview, correct?

Subject:RE: AC-3 stereo volume too low workaround

Reply by: way2slo

Date:4/22/2003 2:46:41 PM

thanks SonicEPM
well i didnt burn a dvd so i cannot tell you. preview is where i hear the pops and clicks. should i render the audio as stereo wave and let DVD-a renders the AC-3?
cheers

Subject:RE: AC-3 stereo volume too low workaround

Reply by: RJC

Date:4/24/2003 3:51:37 PM

Yes, you are correct. At least on my machine I get clicking on DVDA preview, but the renders are fine. I also have not noticed any volume reductions on the final render using the defaults. I am getting a different mix on 5.1 mixes from what I hear in Vegas preview, but there's so many factors involved - codecs, the DVD player, different inputs on the amplifier, etc., that it's really difficult to pin down. It's nothing radical but I notice higher LFE levels and higher front to rear speaker ratios on the final DVD.

-Roger

AMD 1.4GHz, 240 GB video RAID, Creative Audigy, Vegas 4.0b +DVD, Acid Pro 4.0, Pioneer DVD Writer A105 (4X)

Subject:RE: AC-3 stereo volume too low workaround

Reply by: way2slo

Date:4/29/2003 10:14:20 AM

is it possible to import ac-3 stereo back to vegas? if not, how can i playback the ac-3 stereo file? what do i need?
thanks

Subject:RE: AC-3 stereo volume too low workaround

Reply by: swattum

Date:4/29/2003 1:32:27 PM

I think I read that PowerDVD will play an AC3 file directly; I'd imagine WinDVD will as well, but I've not tried it. As far as I know, you can't bring the AC3 files directly back into Vegas - you'll need to run them thru something like BeSweet and decode into wave files.

Subject:RE: AC-3 stereo volume too low workaround

Reply by: Mr_Plant

Date:4/30/2003 4:35:38 AM

That is correct - Power DVD will play AC3 files directly if you drag and drop.

To add to my post (This edit is about a month later!)....

I have done many final masters using the 5.1 encoder now - I always using none,none and -31db and whilst this should not be taken as the only settings to use - it has so far worked great for what I have been doing - your mileage may vary!
I'd always use those settings as a starting point anyway - and see how it turns out.