AC3Filter noise reduction with DTS

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AC3Filter noise reduction with DTS

Postposted on Wed Mar 10, 2010 11:31 pm

As I was playing a DVD with DTS audio today, I noticed that AC3Filter was cutting out/reducing the volume of anything loud (drums, for example). It only does this to DTS tracks; AC3 sounds normal.

PowerDVD 9 Ultra's DTS decoder sounds excellent. Unfortunately, PDVD won't play standalone DTS files such as the 24-bit track I ripped from Tubular Bells (which sounds awful with all that noise reduction).

I did play around with several settings in AC3Filter's config window to no avail. Anyone know how to correct this? Thanks.
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Re: AC3Filter noise reduction with DTS

Postposted on Wed Mar 10, 2010 11:41 pm

Look for a Dynamic Range Control setting and make sure it's set to off or whatever the neutral value is. That's probably the cause, though I don't use AC3Filter myself (at least, not directly) so I can't tell you for sure. :)
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Re: AC3Filter noise reduction with DTS

Postposted on Wed Mar 10, 2010 11:50 pm

Thanks for the reply. Looks like DRC is already disabled. :(
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Re: AC3Filter noise reduction with DTS

Postposted on Thu Mar 11, 2010 12:38 am

Maybe you will find some help in AC3Filter guides
http://ac3filter.net/projects/ac3filter/guides
http://ac3filter.net/projects/ac3filter/doc

There are MANY pages about normalization, matrix settings , gains etc.
And try some settings.

I have analog stereo Dolby Prologic-2 decoder connected and I had to try more than a few setups before finding a proper one.
Mostly for AC3 in video files.
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Re: AC3Filter noise reduction with DTS

Postposted on Fri Mar 12, 2010 3:22 pm

I looked at the documentation, played with ALL of the settings, and got nowhere. Most of the settings did change the audio in (many) different ways, but none of them solved the problem I've been having with "noise reduction." Drums, gunshots, loud noises are still being reduced.

Just thought of something. The X-Fi cards have hardware AC3/DTS decoders--I remember using them under XP and Vista. However, there are no Dolby Digital/DTS tabs in the Console Launcher under Win7. :-?

I enabled SPIDF Output in AC3Filter's control panel, but going by how crappy DTS sounds, I think it's still using AC3Filter to decode.
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Re: AC3Filter noise reduction with DTS

Postposted on Fri Mar 12, 2010 3:29 pm

I was going to ask about this but presumed that you weren't using the hardware since you were doing it in software. ;)

Do your receiver/speakers have any digital processing? I know that my Z5500s have a night mode themselves that (I think) only works on DTS, but I presume given your discrete audio card that you have a more interesting setup than that. :)
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Re: AC3Filter noise reduction with DTS

Postposted on Fri Mar 12, 2010 3:41 pm

What application are you using for playback? Can you provide screenshots of your AC3Filter CP? Am I correct in assuming you're using 6-channel analog output from your X-Fi?

DRC is normally only applied to AC3 encoded audio, so I'm surprised you're having trouble with DTS. It sounds like some type of volume normalization is going on. You may want to try ffdshow tryouts rather than AC3Filter.

SNM wrote:I know that my Z5500s have a night mode themselves that (I think) only works on DTS
Night Mode is for AC3. Dolby Digital encoded audio can contain metadata that enables various levels of dynamic range control, if the decoder supports it.
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Re: AC3Filter noise reduction with DTS

Postposted on Fri Mar 12, 2010 4:05 pm

Ah, I guess I had them backwards, then.
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Re: AC3Filter noise reduction with DTS

Postposted on Mon Mar 15, 2010 2:03 am

According to Creative, my X-Fi Titanium Pro never supported AC3 and DTS in hardware, so I don't know where my vivid memories of a hardware-decoded past are coming from. :-?

However, I did fix the noise reduction problem by downgrading to an older version of AC3Filter. It still doesn't sound as "clean" as Cyberlink's decoder, but it beats putting in the damn DVD and losing a few hundred MB of RAM.

@CrazyBus. Thanks for the link. I haven't tried ffdshow yet, but will tomorrow. I am using WMP12 and analog speakers, btw.
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Re: AC3Filter noise reduction with DTS

Postposted on Wed Mar 17, 2010 3:30 pm

This has nothing to do with my original topic, but here's a tip for AC3Filter users:

Open the AC3filter control panel, click the System tab, and under "Use AC3Filter for", uncheck PCM, LPCM, and MPEG Audio.

Yesterday when I was listening to Carly Simon's No Secrets (5.1, 24/96 FLAC I ripped from DVD-A, since Creative doesn't support it under Win7 :( ), I heard quite a bit of distortion in the vocals. Upon dragging the file into GraphEdit, I saw that AC3Filter was also handling the PCM output from FLAC files. After disabling PCM and LPCM in AC3Filter, the distortion just vanished. A lot of my other music sounds noticeably cleaner as well.
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