surround and stereo

[Frank Ladner]

I am using DVD Architect 1.0 and, as far as I know, don't have the ability to allow the user to select from multiple sound tracks (5.1 and regular stereo).

So...I was wondering, if I simply mix all my sound out as 5.1, AC3 (I think) and leave it as that, will that work on a regular stereo sound system? ie. will the sounds mixed to the front speakers in the 5.1 mix come out of the regular speakers?

I understand that if this does work, I'd have to be careful about mixing the sound, so that some important sound elements (especially dialog) aren't completely in, say, the back speakers so that they would still be heard on either setup.

Any advice on how to do this would be really appreciated.

Thanks!

,Frank

[Edward Troxel]

Yes it will work. The DVD player should automatically downmix to stereo.

[Frank Ladner]

Thanks, Edward! That's what I was hoping to hear.

I will give it a try.

[Peter Jefferson]

with Dolby (here we go... ) there are many elements which can be added to the stream...

if your original AC3 is rendered within something liek Vegas, you wont have a problem with what i am about to explain.

Pls bear in mind that im working by memory here, so i may miss afew things...

okies. first off your right, DVDA DOESNT have multiple audio streams.. hopefully DVDA2 will, but for now well work without it...

ok.. youve got yoru poject in vegas and you want audio as 5.1 then a mixdown to stereo for those that dont have it.. cool..

Like ed said, most players will crete a downmix.. however some players do not have a Dolby Digital decoder built in. these players usually only have an optical/coax out and run the ac3 directly from disc with no buffering. this is where the surround amp comes into play..

now Eds right, no doubt, but there are afew things to keep in mind..
Dolby Digital canm carry extended bitstream info. What this means is that YOU can configure the stream to include info on
"what it does when its mixed down"
Pretty hard for me to explain here..

umm.. ok here ges
-Ok, youve got a 5.1 encoded dvd..
-client has stereo...
-DVD player set to stereo or analogue out.
-They wack the disc into the player.. its all good...
-DVD player picks up extended bitstream data from Dolby stream.
-This data carries info in compression rates as well as phasing and mix levels for each stream/channel.
-Dolby Decoder within the player or amp recognises this data and adjusts the actual decoding routine to correspond with the data YOU have added. Mix rates and phasing is switched to YOUR preconfiguration of the stream.
-This kicks ass, coz the default levels set by the player are usually set to -0dB on all levels, or carry no data for mixdown, so u get a mush of 6 channels mixed into 2...
-In turn, with the Dolby Digital EX, your mixdown will be set the way the Author (ie YOU) have set it to regardless of the player config.

this is as basic an explanation as i can write up..

[Frank Ladner]

Peter: Wow! Thanks for that thorough explanation.

So...since I am doing the audio in Vegas, I don't have to worry about that, as you mentioned? ie. the extended bitsream is configured such that the levels are properly set to come out ok on a 2.0 setup?

Thanks a lot for your help!

[Peter Jefferson]

extended bitstream is usually swiched off by default within vegas due to many people not being educated in its uses..

Extended bitstream is a series of commands also known as Metadata and it has no effect on the actual sound data within the ac3 when output to 5.1.
Think of it as a washing instructions tag for your new shirt....

you do NOT need extended bitstream configs to get stereo output. Your Decoder should be able to handle the downwmix on its own..... BUT with the downmix, EX lets YOU decide how its done.

Dolby Digital EX is there for people who create 2 seperate mixes of the same content or Mixdown content (usually the latter).

one mix is 5.1, the other is Stereo (usualy for different setups NOT including 5.1, virtual surround within tv's etc)

Basically, i can have a 5.1 mix, add numerous effects on any channel (reverbs, ricochets from bullets echoing etc etc) Now, in 5.1 these would play fine and my effects would go to each respective channel as i want them to...

in stereo though, when you include all the LFE, and 5 other streams of audio, you can get a mish mash of noise and its not nice.. especially with reverbs, and other LFE going off... frequency bandwidth just gets overloaded and its shite...
This is where EX comes into play...

In lamens terms, you can literally say to the decoder..
"ok, heres my 5.1 ac3.. but if someone runs this as stereo, i only want the rear speakers to output XdB of volume.
I also want to drop the LFE volume by XdB. THEN you can mix me into Stereo"

When the decoder (amp or DVD player) reads the ac3, it will recognise these commands. Then it will configure the output according to waht u have set up.

NOW if you run this EX config within a Pro LogicII environment for setups using 6.1 and 7.1 these commands will extend to those channels in accordance with the Amplifier.. YOU'RE not giving any data for these other channels.. your only providing a 5.1 with info on stereo mixdown...
The amp does the rest...

usually 6.1 combines both rear speakers
7.1 is usually a combination of rear surrounds and front stereos
These of course can be configured for phase shifting, dimensions, panoramics and distance (depending on the amp)
When encoding you DONT need this unless your working within a Cinema output frame of mind..
And if u were doing cinema, id ditch Vegas and go for something like a Dolby EX-EU4 Encoder & EX-DU4 Decoder used with the DP569 Dolby Digital Encoder and DP564 Multichannel Audio Decoder.
Thats expen$$$$ive high end shit though..

hopefully this has cleared some uses for Dolby Digital EX (extended bitstream)
By the way, there IS NO METADATA on a stock standard AC3 from Vegas.. but mixdowns are usually configured with a -3db output due to most downmixes going thru analogue sources.

theres alot of info im skimping on due to time and laziness :) but thats pretty much it in a nutshell...

[Frank Ladner]

Peter: Thanks! I get the theory of what you're saying - to basically tell the decoder how to downmix (ie. if downmixing to stereo, drop the volume on rear channels, etc).

"By the way, there IS NO METADATA on a stock standard AC3 from Vegas" <--- and there's no way to include this in Vegas?

btw, I'm not mixing for cinema, so the high-end tools aren't necessary. Is there an inexpensive software solution that you can recommend for me?

Thanks a lot for sharing your wealth of knowledge!

[Peter Jefferson]

btw, I'm not mixing for cinema, so the high-end tools aren't necessary. Is there an inexpensive software solution that you can recommend for me?


your already using it mate :)

as for the metadata, when u render your ac3, you can include this metadata/EX info. what i meant by stock standard is "default" ac3 render settings.
Anyways,.. its the 3rd tab form the left.. its called Ext. Bitstream (which surprised me when i first saw it.. i wasnt even expecting this..
SoFo Soft Encode didnt even have this from memory.. mind u im goin back to Version1 ....

anwyays thisis where u can enable it and tweak it to your hearts content :)

dont forget if ur doing downmix prefered files, you should also tweak the dynamic range compression factors in accordance with the final output ... You can set compressions and rooms types here

good luck with it

One thing to note, is that this works better if your dvd player DOESNT have a built in decoder.. some do.. like the ol cheapo but brilliant xms750... cheap dvd playuer, but it has THE best audio config ive seen in a dvd player.. but thats off topic so ill shut up

[Frank Ladner]

Ok, so I CAN do this with Vegas - just not with the default templates. Gotcha. I'll check that tab out and see if I can make sense of it.

You have been a huge help! Thanks a lot!