[microsound] re: how to create 5.1

[ニコラス・ケント <ndkent@xxxxxxxxxxxxx>]

There are two separate processes involved.

The first process is just creating the 6 audio channels. There are  
huge numbers of tools you can use from free to very expensive. Since  
you already have stereo material then you want to look at what tools  
you get in terms of mixing . Certainly a lot of tools can deal with 6  
tracks at the same time just as they should also be able to apply  
effect instances to all 6 tracks. The finer detail is ideally you  
want mixing and effect tools that process the entire sound field in a  
coordinated way not as 6 synchronized tracks, unless that is fine for  
you. Most of the high end sequencer apps have tools that address 5.1  
and if you have the programming skills or ability to find existing  
patches that give you want then PD, MAX and other programming based  
environments might get you what you want. I never looked into it too  
deeply when I was looking into Mac info, Bidule came up a few times  
in other's mentions of multichannel effects and positioning.

Oh, and it's worth noting that while I think Apple Soundtrack  
addressed some issues in a recent update, I remember they were  
roundly criticized in the past for calling themselves a "pro" app and  
only being able to work with surround by using undocumented  
workarounds or something.

The second process is delivering our audio. If you are delivering  
direct from a computer with software that can play back your  
multitracks then there is nothing more to deal with except being sure  
the system where you want to deliver it works.  The other approach is  
to get it on a disc that can be played. I guess there is also 8  
channel tape, digital or an analog.

Clearly the system that is most out there is a regular DVD. I guess  
the downside is you might need a surround decoder as some DVD players  
have 6 analog outs while many just have a digital out that needs to  
be decoded by external hardware. The other downside is that regular  
video DVDs use lossy Dolby AC3 compression for surround audio which  
you may or may not take issue with.

As someone mentioned Apple Compressor has the AC3 converter bundled  
with it (Compressor itself is bundled with Logic Studio and Final Cut  
Studio). It's actually a separate app that gets launched for what  
that's worth, but it needs Compressor run. As I understand it, AC3 is  
patented so you won't see it in an open source or budget DVD burning  
app. On the other hand it is frequently bundled or included with pro  
apps.

DBX, a Dolby rival came up with their own lossy system with a  
hardware decoder. I've only seen PC tools, but a possible usable for  
something option is it is possible to author a CD-R containing a DBX  
surround data stream and deliver it on a standard DVD player with a  
hardware DBX decoder (internal or external). I'm not sure how real  
world useful it is (not open source or that cheap) given there are  
not that many DBX decoders out there, but it might be an option in  
some circumstance.

Another DVD option someone mentioned is DVD-A (DVD-Audio). It's  
uncompressed but is pretty rarely seen. A small handful of tools to  
create a DVD-A disc exist for PC users but are many times more rare  
than standard DVD tools. My understanding is when the spec was  
formulated went and chose a lossless codec (Meridian) for surround  
that is seriously expensive to license to developers, hence in my  
opinion shooting the format in the foot. (No content, no player  
sales) I guess Blu-Ray might be an option one day for audio delivery,  
once affordable authoring tools are released or perhaps an audio spec  
is introduced for high end audio deliver. I don't see DVD-A reviving,  
which is a bit of a shame.

nicholas kent


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