Level Discrepency DVDSP to the DVD

hi,

apple g5 QUAD, running OS 10.4.7; Compressor 2.1; DVDSP 4.1.0

i am an audio post professional and understand most of the concepts involved here. i have had DVDSP both v3 and now 4. i have created AC-3's for films and programs for about 2 years...

now, i created Stereo 2.0 AC-3 files using compressor : SR 48, 448 kbps, Complete Main. diag norm -31, ALL pre-processing junk OFF

when i audition it in DVDSP using DIGIDESIGN CORE AUDIO it plays back fine (some peaking about -6 at most). i have a set of very accurate meters.

i burn a DVD and play it in the Apple DVD Player, using DIGIDESIGN CORE AUDIO, it is almost 6dB LOUDER!!...and, in fact, on some occasions the decoding compressor kicks in and there is ducking going on.

so, i tried -27 ...same thing...LOUDER.

if i use a PCM file, the level stays the same. problems is, that eats up bandwidth.

quieter i understand. but louder? i am sure this is a de-code rather than encode problem.

anybody have a clue as to what the problem is? or where i can go to find an answer?



tom hambleton, C.A.S.
minister of fancy noises

"Entropy ain't what it used to be!"

To me your workflow seems ok.
Try with a commercial feature film DvD to check your levels.
More then probaly it will go to loud as well.
I know this won't solve your problem but you'll know for sure if it's a decoder/playback problem.

Grtz,
Chris

In the settings for DVDPlayer, have you got the button to disable the Dolby dynamic range compression checked or unchecked?

Hal MacLean wrote:

> In the settings for DVDPlayer, have you got the button to
> disable the Dolby dynamic range compression checked or
> unchecked?


DING DING DING !!!!!

we have a winner. yes, THANKS! the "Disable Dolby Dynmaic Range Compression" was NOT checked, so, the DOLBY compressor was on during decode... and it REALLY screwed things up.

i disabled it, and everything plays back perfectly!

thank you!



tom hambleton, C.A.S.
minister of fancy noises

"Entropy ain't what it used to be!"

Ok, I did some more digging and found out what is going on.....in case anyone is interested...

Turns out Apple's DVD player IS working to Dolby's specifications.

Dolby Digital decoding has three possible modes: Custom, Line, and RF. Line mode is used for hardware with "line outputs" which is nearly 100% of standalone hardware DVD players. Custom mode is sometimes available in home theater receivers and allows the amount of dynamic range compression to be scaled by the user. RF Mode is for products that (quoting Dolby's decoder licensee information manual) "deliver the audio via a path with very restricted dynamic range."

Dolby's decoder licensee information manual defines various product categories for decoders. One of those categories is "Personal Computer Products." Dolby recommends that this category use "RF Mode" decoding "if the amplifiers and speakers have very limited capability." Apple computers have limited capability speakers in them. So, I am pretty certain Apple's DVD Player uses RF Mode decoding. Further more, I am pretty certain RF Mode compresses heavily with make-up gain to make it so you can hear a movie soundtrack adequately with crappy computer speakers.

I hhoe that Apple improves its DVD Player preferences to allow you to use Line Mode when you are using the computer's line outputs instead of the built-in speakers.

And now you know, "the rest of the story"!



tom hambleton, C.A.S.
minister of fancy noises

"Entropy ain't what it used to be!"