Steve Harris wrote:
On 13 Mar 2007, at 09:15, Valent Turkovic wrote:
Hi,
is it possible to record multi channel speech audio and down sample it
2 stereo channels BUT with horizontal audio positioning of each audio
channel ie. like dolby surround effect.
Sure, but you might be disappointed by the results, Pro Logic is not
very sophisticated (eg. there's no separate rear left and right channel,
and the bandwidth is limited). Also the only free software
implementation that I know of is not state of the art, partly due to
patent problems, and partly due to lack of interest.
There's a LADSPA plugin:
http://plugin.org.uk/ladspa-swh/docs/ladspa-swh.html#id1401
which does Pro Logic matrix encoding, you will need some other software
to mix your independent streams into LCR channels (you can do it by ear
with a 3+ variable send bus mixer), but once you have that you can feed
it to the plugin and get a pro logic compatible stream out.
PS ignore the documentation, it has been tested, and it does work, just
not brilliantly. You will get better results if you EQ the mics a bit to
cut the level of the highs and lows a bit, especially in the rear channel.
You would get much better results with an ambisonic stream, but I don't
/think/ you can make stereo-compatible ambisonic streams, and not many
people have ambisonic decoders. Other people on this list know a lot
more about ambisonics though.
i'm very new to ambisonics, so i may be wrong, but i think there are
indeed stereo compatible first-order ambisonics streams. iirc, the
format is called UHJ, and it matrixes WXY (lossily) into L/R (i.e. no
height information).
i've changed the subject to bait fons :-D
if we're lucky he knows an implementation of 2-channel UHJ.
i found this article: http://www.ambisonic.net/ambi_AM91.html
but it does not give details as to how the matrix encoding is accomplished.
regards,
jörn
