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Old 26th December 2003, 21:24   #259  |  Link
kempfand
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Join Date: Oct 2001
Location: Switzerland
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Conversion between UHJ and B-format using SIR (Super Impulse reverb)

From Shayne Dec 11:
Quote:
What we need is all this put together in a MP3 player that joins all these filters and outputs a play list to a temp.ac3 file in small chucks and then sends them out spdif. The 3 gain filters can be user adjusted and voilą a player that would definitely out play anything we have now. I am sure its thought of and in the works.
I think we are basically there. At least for "wav/mp2-in" --> "6-channel-out", it works beautifully here with Bidule and SIR (Super Impulse reverb).

A few (selected) details on the SIR-VST:
Code:
- This is a reverb device that works with "impulse-responses".
Impulse-responses are generated by recording short, broadband
signals and their corresponding room-reflections, and by cutting
out the initial signal. What is left contains the information
needed to reproduce the same room with other signals.
- SIR is a stereo plugin. To take full advantage of
stereo impulses for mono signals, you must first convert
the track to stereo.
- Features:
  - performance optimised
  - wave-file import 24-32 bit
Angelo Farino already published an outline Conversion between UHJ and B-format using SIR for AudioMulch, which is pretty self-explanatory, so I wont' dulpicate here.

I've written a small bidule which does the same as outlined Audiomulch contraption (I can upload it to Daphy's ftp if there is interest).

In summary, this achieves the same as the initial Ambisonic Guide by EoH , but with the new tools in real-time (or "hyper-speed" with the offline-mode).

A few notes:
- make sure you use the "right" impulses with your source (i.e. 44.1kHz 32-bit pulses on source=stereo_wav with same properties)
- "M2Buss" in AudioMulch translates into "AudioMatrix" for Bidule
- I personally prefer Bidule, but this is my personal taste (think it's more intuitive to use, more straight-forward)
- Filtering-impulses are also available from A. Farina's Site
- You might want to play with the settings for 'dry' and 'wet'. As a starter, I recommend 'dry'= 0 dB, and 'wet0= -6 dB.

Cheers,
Andreas
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