Community Forums Archive

Go Back

Subject:Noticable loss in highs and lows
Posted by: LoTN
Date:7/7/2010 11:52:08 AM


This is with VP9c and the pro encoder:

Using the default AC3 for 5.1 DVD A, I can easily ear big loss in low and high frequencies. I haven't yet tried to perform some spectral analysis but it looks like some band-pass filter is applied to gently cut below 80 and above 10k.

I wonder where I am wrong, should I apply some specific curve to masters before encoding ?

Any help would be appreciated.

Subject:RE: Noticable loss in highs and lows
Reply by: musicvid10
Date:7/8/2010 10:01:03 AM

You're not hearing frequency loss, you are hearing DRC. The default AC3 template is uhh, less than ideal.
Here's the post from 'way back.

"I've run some exhaustive tests with calibration test tones and done extensive reading of the Dolby metadata specs, and in reference to your question about the most accurate reproduction with the AC-3 Pro Encoder, I am prepared to make the following recommendations with notes:

If you're doing AC-3 Stereo, you can ignore everything I say about the Phase Shift option, it's greyed out of course.

Dialog Norm at -31 (this sets it at unity gain)
RF and Line Mode DRC Off (WYHIWYG)
DC High Pass Filter On (this operates at <=3Hz and takes DC bias out of the mix)
Bandwidth Low Pass Filter On (this takes aliasing noise at >20kHz out of the encode, but it also lowered the rendered volume by -0.1dB in my tests)
90 Deg Phase Shift On (makes it easier for Pro Logic decoding on older equipment, Dolby says it is inaudible in 5.1 except in "very rare" cases)

Message last edited on7/8/2010 10:02:02 AM bymusicvid10.

Go Back