On 27/10/2012 23:27, etienne deleflie wrote:
..
I really didn't want to get pulled into a defence or argument about
ambisonic formats ... but, just to clarify ... the choice to include
some empty channels in UA is intentionally designed so that authoring
environments don't need to change all the channel routing when working
at different orders. The choice of Wavepack was determined on its
ability to compress empty channels to take up no space. Wavepack also
efficiently losslessly compresses all sound data.
Yes, what it does, it does very well. However, as described, you are
asked to first create an n-channel interleaved WAVE file containing all
those uncompressed silent channels, and pass that to wavpack. Which is
fine in principle, except that with a possibly large number of channels,
the 4GB limit of WAVE will get exhausted very easily. Wavpack ~only~
recognises a standard WAVE file (i.e it does not make any use of
libsndfile etc), it knows nothing of CAF, w64, etc (to say nothing of
AIFF files). I have already had emails from otherwise happy toolkit
users hitting the 4GB limit; which will of course have to be the next
not so incremental update - implies making a 64bit version of AMB too :-).
So a custom tool to create wv files will be needed, to interleave N mono
files, with some system to indicate empty channels (e.g. as supported in
the toolkit program interlx), and generate the wv file directly. The
problems then compound, as such a file can't simply be unpacked to an
N-channel wave file if it exceeds 4GB.
So I guess the bottom line is, YMMV.
Richard Dobson
PS: re output channel ordering - you might be interested in my new
version of "paplay" in the toolkit - includes an option to specify the
routing of one or more file channels to device outputs, with zero
indicating a silent channel. So you can play a 4-channel file "abcd" as
"dcba", "b00d", "a", "cb", etc.
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