downmix problem

[minister]

finished a 5.1 mix and everyone is happy. it was printmastered and the SR sounded fine. for the DVD, i am providing 5.1 AC3 and a stereo AC3, using a.pack. i don't have a down mix plug-in. so i used the following method: L,R panned accordingly at unity; C down 3db; Lfe down 10db and panned center; Ls, Rs, panned accordingly and down 6db.

with either the APPLE DVD player in a computer, or my consumer deck, the 5.1 downmix to stereo is superior -- clearer, less phase problems, more dynamic than my stereo file. meaning, a DVD deck will automatically downmix a 5.1 mix if you do not use the optical or the 5.1 analog outs, and just use the stereo outs. WHY? what is a better method for me?

the mix has a lot of water annd boat sounds that sound phasey very quickly and the stereo mix sounds like certain things are masked.

i do have Dolby Surround tools, but i thought that was for broadcast and game surround encoding. (guess i should read the manual...)

[filmixer]

I would definitely use the Dolby encoder to make the LtRt. Version 3.0 and higher that runs on HD hardware works great and will give a better experience to people using a Pro Logic decoder to watch your show. When you set up your routing to the encoder, make mono subpaths for LCR. The encoder will handle the center channel properly. When you set up to combine the surrounds to mono, leave them at 0db or -3db (whatever sounds best). LFE at -10 is good. Try it, you'll like it.

[CCash]

Minister-
Not that this will avoid phase issues... but, did you send the center channel out of a discrete output, or was it sent to a stereo output or bus? If you sent it stereo, and panned it center, remember that PT will lower the signal 2.5 dB (pan law). Lower it only .5 dB to get -3 total. You're probably on top of it, but it's worth mentioning.

And I agree with going with the Lt/Rt

Curt

[minister]

curt,
thanks for the reply. i did know about PT's pan law convention. yes, at first i brought it down 3 and then went, oh, right... .5db. but i wrote -3 because i was thinking that was the sum attentuation. and yes, i was putting it into a stereo bus not a discreet output. do i bring it down only .5 when i am using the Dolby Plug-in? ( i suppose that is in the manual...)

the phase issues are the electircal (not acoustical right?) summation of some portions of the surrounds into the fronts. right? so..the LtRt using the Dolby Surround tools will deal with that? does it induce some delay into the surrounds?

i am off to master the dolby surround encoder... stay tuned.

[GTveito]

Remember that the LFE channel is not included in the Dolby Digital DVD stereo downmix, so you can´t compare it directly to LtRt. The LFE is +7db according to the Dolby settings. -10 db would give you something in between the DVD downmix and LtRt.

Gisle Tveito
www.norskfilmstudio.no

[georgia]

Hey minister... We still have the mix here... do you want me to create a downmixed version for you?


cheers
georgia

[Sonsey]

Hey minister...

Two questions:

1. Did the downmix sound right coming out of your PT rig?

2. And if so what data rate did you use in A.pack?

I had a similar problem with one of my projects and it turns out that A.pack likes to encode Stereo files at 192, and I was using 448 (thinking more had to be better). Might not be your problem... then again it might....

[minister]

hey howard!!

no, it never sounded quite right coming out of PT. i DID encode it using the higher rate of 448 -- it sounds better than 192 and, the movie is a short, so there is room for it. do DVD players have a some kinda Dolby decorder for downmixing built in? they must.

my issues are more phase combinations causing things to get muddy in a few spots, so the detail and clarity is sacrificed. i am in the process of learning how it will work with Dolby plug-in and taking into account home and broadcast viewing. specifically (and i tried this before i used the plug in) of delaying the surrounds. with the plug, i am playing with the delay trying things from 10-20 ms and even automating it in spots. i have one really bad section, so i am playing with sneaking the sound for that 15 seconds into the front and not worrying about the LCRS playback image for that one scene. the film will be fine with out that steering being representational. i zoomed way in and the phase is coherent on my one sound, but the fronts are causing a conflict that i will never solve by manual surgery.

the other thing i am doing is multing the LFE and panning it hard left and right to see if i can't better anticipate a home viewing without LCRS. i am playing with the level...starting about 9db down and listening and adjusting from there.

i was just hoping i wouldn't have to REMIX. problem is, also, the nature of the sounds, boat motors, water and lake ambinece. a real recipe for phase incoherency!

[TVPostSound]

Minister

Email me your email address.
Its in my profile

[minister]

thanks to all who helped me with this, filmixer, sonsey, georgia, diafxmx (am i forgetting someone?)!! your advice proved helpful and i solved my problem with a variety of methods. i ended up using dolby surround tools (after reading the manual ... they put all kinds of useful information in thise things ) to create an LCRS and i rode the sourround delay from 10 -15ms in certain sections. then, in my one problem area, i swapped the phase on a surround. i also snuck some things up into the front in a couple spots and rode some levels. then made the LtRt form the LCRS. i have to do a more complicated project in february, so i will file away all your suggestions for then.

i almost recorded the mixdown out of my DVD player, 'cause that sounded pretty good. then i thought, oh boy, sync issues. i suppose it is just like playing it out the DOLBY encoder/decoder box...