[vorbis-dev] Calling for 5.1 Mastering experience! (vorbis ambisonics and 5.1)

[Ray Heasman]

Hi,

I am not an expert in this, but my sound engineer friend suggests this
link as a potential answer to your question:

http://www.mkprofessional.com/bass_mgmt.html

Hope this helps,
Ray

On Tue, 2003-06-10 at 13:30, Gregory Maxwell wrote:
> I've been doing a fair amount of work with Vorbis support for Ambisonics,
> which seems to be going along nicely. It seems that there is signifant
> interest in coding 5.1 material with Vorbis esp as tarkin becomes more
> complete, so I've decided to take a break from pure ambisonic work to look
> into this.
> 
> I've decided that the best (from a pure elegance and patent avoidance) way
> to handle this is to basically decode the 5.1 input into a WXY or WXYUV
> ambisonic signal, which can then be handled by the Vorbis Ambisonic support.
> 
> To accomplish that I produced a model of an idealized 5.1 speaker
> arrangement (with pointsource massless speakers) and a simulated ambisonic
> microphone at the listening location. I then measured the ambisonic
> impulse response from each speaker and produced convolution filters for
> the audio.
> 
> The nice thing about this is that you can take the ambisonic decoded
> output from vorbis and convolve it with inverse of these filters and get
> pretty much the orignal input back or you could also convolve it to match
> your own speaker layout and get better results than you would with the
> orignal 5.1 material.
> 
> My only problem right now is with the LFE (subwoofer channel). I had been
> intending to just mix it into the W signal, which I think matches the
> intent of the channel. Obviously this really couldn't be recovered on
> decode.
> 
> My alternative is to use a seperate LFE channel in the vorbis stream,
> which is just ugly.
> 
> So, what I'm looking for is some guidance about how the LFE is normally
> and best used in 5.1 mastering. If I had an infinite supply of perfectly
> flat really loud full spectrum speakers and I was setting up an ideal 5.1
> setup, would I mix my LFE into my five speakers, or would I grap another
> one of those perfect speakers and lay it in the corner with the LFE feed
> going into it?
> 
> 
> 
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-- 
Ray Heasman <nurf at spamcop.net>

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