I have a large collection of B-Format (WXYZ) ambisonic WAV files, which I would like to process down to stereo. Is there an accepted way to achieve this? My attempts at doing this myself, using some of the more pedestrian filters available in CLI tools like SoX and FFmpeg, have predictably resulted in the W channel being mapped to L and the X channel being mapped to R. Not ideal.
Does anyone out there have an elegant solution to this issue? I am hoping to achieve this without having to leverage a DAW, despite how unrealistic such a requirement may be.
Many thanks!
Sadly, I am not expert in ambisonics but I have used it at home for the last 30 years for playback and have picked up some useful bits. Luckily, my DSP can play back horizontal B-Format correctly. I can't make use of the Z (elevation) component.
I think you will have to convert B-Format horizontal back to A-Format and then you can produce virtual mic patterns to taste (e.g. fig 8, cardioid, etc.). Have a look at the Wigware VSTs. I'm pretty sure there are others. Otherwise, in B-Format adding X to W gives a front facing cardiod (-X to W = rear facing), adding Y to W gives left facing (-Y to W = right facing). Horizontal B-Format is basically an omni (W) coincident with a front-back fig 8 mic (X) and a left-right fig 8 (Y).
I fly an armchair most of the time so hopefully what I've said is sort of correct.
Simple M+S Stereo
This is a simple decode equivalent to a M+S microphone array at the
listening point. This works better than a front-facing arrangement for
many (but not all) purposes. Note that there are /lots/ of ways to do
stereo decodes of B-Format. Also, see more on "Synthetic Microphones"
below (this decode is equivalent to two side-facing cardioids, though
we've halved the gain).
W In Y In
Left 0.7071 0.5000
Right 0.7071 -0.5000
(via wayback via blueripple )
What junh1024 says:)
Since reflecting front-back or up-down in stereo playback is problematic you can just ignore it and have simple equations:
L = (W+Y)/2
R = (W-Y)/2
In the end, the method you use can be as much an artistic preference as a technical one.
Could foo_channel_mixer do this? (Too lazy to try, don't know if it still works: http://skipyrich.com/wiki/Main_Page )