Paul Hodges wrote:
--On 29 July 2013 03:57 +0100 Stefan Schreiber <st...@mail.telepac.pt>
wrote:
UHJ (surround/3D audio) as extension of stereo based files
(distribution via Internet, on discs and streaming, including
YouTube, Spotify etc.)
I like the potential of this idea very much; but it can only move
forward with the free availability of freely available encoders and
decoders for 2, 3 and 4-channel UHJ, in both standalone and plugin
formats. Seeing as how mere 2-channel versions have signally failed to
become available at all, I wonder what chance there is.
I had hoped that somebody else would state the obvious, in the end I
have to do this myself... :-)
While I would understand the above argument IF UHJ would be some area on
its own, my proposal actually implied that you would use (in the end) a
B format decoder.
You would < additionally > need an UHJ channel extractor (works on the
AAC file/ .M4P/Ogg etc. < input > ), and secondly the UHJ to B format
"translator". (The latter is just the application of some formulas which
might not be trivial but are known and/or can be deduced. From an IT
perspective, this is very little program code. You just have to apply
known formulas. This step also doesn't depend a lot on the specific
programming language which is used. Mathematics stays mathematics, and
the "language" of mathematical formulas is older than programming
languages - which explains why formulas look more or less the same in
any programming language - well, if I/you exclude Forth and other
exotics.... :-D )
I would call the two additional steps the < UHJ front end > for some B
format decoder.
I know that there would have to be done a lot more work to publish B
format programs/plugins/mobile apps etc., and to describe B decoder
design. Specifically, I believe that B decoders nowadays < should > be
able to support output via headphones and binaural techniques. Section
III of my 1st posting suggests that head-tracking hardware is both
available and cheap enough to be applied in real-world products,
including future < surround capable HT headphones >. I mentioned the
specific hardware used in the Oculus Rift VR headset, just to give some
example for some existing HT chip. (There is plenty of other hardware
around.)
It might help to set up some open group, which would promote the use and
design of B format (HOA? Section II...) decoders: describing the theory
behind, offering (open sourced) program code, distributing free
solutions etc. (To set up a working "open" group requires some
organisational skills, but it can be done.)
Again, the real problem seems to be the lack of available B format
decoders. (My proposal is to transport "B format over stereo", in some
simple description. If so, it is again obvious that you should see the
use of UHJ extension channels just as a front end for B format, because
this is the format which has to be decoded.)
I believe that "you" should promote the fact that B format is a real 3D
audio format, using just 4 channels. This is obviously some intriguing
fact. (Note that the spatial "3D" resolution of full FOA is actually the
same as the spatial 2D resolution of XYW, because Ambisonics is isotropic.)
IMO, 2-channel UHJ is something from the past. Don't use this if you
could distribute the real thing?! Which means B format, not a reduced
form of B format. The use of 3/4 channel UHJ (maybe more channels for
higher oders) was suggested to stay compatible with 2-channel
audio/stereo files and streams. It has been shown that existing
file/container formats would allow the transport of < UHJ<---->B format
> over stereo, via at least two different extension techniques. (File
extensions, extensions in current container formats)
Best regards,
Stefan
P.S.: Mpeg Surround is also a decoder based design. (MPS encoder/decoder)
The same is valid for the future (Mpeg) 3D audio codec, currently in
development. I know that they take the topic "binaural output via
headphones" very seriously, you just have to look into their CfP and
similar documents...
P.S. 2:
Like everyone else I wish I had the time myself; but when factoring in
the need to learn about DSP programming and modern programming
languages, other commitments, and the slowing down of age...
Paul
Not any single person could do all the programming stuff, at least not
anymore. There are just too many different platforms around....
Nevertheless, B format decoders/apps will be written if Ambisonics is
seen as a format which is worth to be implemented. (Or if there is
enough music in this format around.)
In this sense, I would look to the applications/aspects which are
"beyond" of what is offered by the 5.1 ITU layout. (IMO Ambisonics
starts to shine if you factor in the inherent capability to
record/encode < full-sphere> 3D audio. And because you could really not
expect that available 3D audio loudspeaker layouts would look about the
same everywhere, the Ambisonics decoder can be seen as a necessary
interface to real-world loudspeaker configurations, or to headphones.
2nd advantage... More arguments?!)
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