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AC-3 Encoded audio is badly affected by DRC

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Jintae Joo
AC-3 Encoded audio is badly affected by DRC
on Aug 4, 2011 at 4:03:08 pm

Hi, I had problem with audio in DVD authroing,

The problem is,

When I received sample DVD authored by our authoring company,
The volume was lower than original audio that I mastered,
And there was limiting effect that pumping sound
for example sea wave sound became louder than original,
and spaceship's sound became lower than original...

the company said they encoded with default options
(Dialog Normalization -27dBFS, Preprocessing Film Stanard Compression)
They said they use hardware encoder

So I googled about AC-3 encoding,
And I found this problem is related to Dialog Normalization and Dynamic Range Compression.

I encoded by Apple Compressor by my own,
and I tried many cases,
and I got 2 best solutions but still I couldn't solve the problem...

Basic Condition:

My mixture have peak level up to 0dB
and average level is around -6dB~-8dB
And surely I have 48khz, 24bit WAV files and AIFF files..

Case 1.

Original file with peak level 0dB,

Dialog Normalization : -31dBFS
Bitstream Mode : Complete Main
Preprocessing : none

(I've changed Bitstream mode to 'Music and Effects' but there were no changes)

I tested in:

1) MAC OSX's DVD Player

DVD Player has option named 'Dynamic Range Compression'
When this option is on,
I could hear limiting effects but it was better than the company encoded.

When I turn off the DRC option,
DVD Player played my contents originaly.

2) Cyberlink Power DVD

seems to same as original.

3) Sony Playstation

same as original

4) Samsung Blu-ray Player

same as original

Case 2.

I reduced mixtures down to -3dB.
Dialog Normalization : -22dB (31 – average volume 6 – reduced volum 3 = 22)
Bit Stream Mode : Music and Effects
Preprocessing : none

1) MAC OSX’s DVD Player
It seems to same as original even DRC options is turned on,
But when the option turned off, its volume was too low. (about -6~-10dB lower than turned on)
However the sound was very comfortable just my feeling.

2) Sony Playstation & Samsung Blu-ray Player
The volume was too low.
And when I changed TV’s volume up the quality of sound doesn’t seems to be good.
But it seems the limiting effect wasn’t there anymore.

3) Cyberlink PowerDVD
The volume was too low also…
But the sound was comfortable.

Is there any solution else?
I’ve tried many cases more than this…
DialogNorm -27dBFS on 0dB Original, DialogNorm -31dBFS on -3dB Original, Dialognorm -25dBFS on 0dB Original… etc….

I’ve checked OASIS’s Time Flies DVD (it uses Dolby Digital audio too) but its sound was perfect and I didn’t found any problems there…




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Andreas Gumm
Re: AC-3 Encoded audio is badly affected by DRC
on Aug 8, 2011 at 5:29:35 pm

Don't apply any global DRC profile to AC3 streams.
This will keep you awayy from such issues!

Andreas Gumm
selfemployed media author

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