Michael Chapman wrote:
(Continuation of: The commercial future of Ambisonics, 15/5/2013)
[ ... ]
If this is a proposed standard, then I would say:
-BHJ (2 channel) should not be used
I do agree. (Unless for legacy reasons, because sometimes the B format
source might actually have been lost. Which means the BHJ version is all
what rests from your Ambisonic recording or mix.)
-SHJ (2.5 channel) should not be used (is bandwidth really a problem,
except for radio, these days?)
Just some ammendment to my former posting: The proposed "UHJ extended
stereo file standard" (AAC etc.) would certainly work well for DAB
radio, which actually would imply DAB+ in this case. (DAB+ is using
AAC/HE-AAC, within DAB spectrum and modulation standards.)
However, DAB (and generally speaking, digital terrestrial radio) has not
exactly been some "roaring success", and this after so many years of
existence... From a consumer-perspective, it doesn't add anything
really "new" to FM, because FM and DAB both (functionally) offer the
same thing: stereo broadcast. (Ok, you have the possibility to transmit
more radio channels. And "much more" if you lower the transmission
quality, which tends to happen because the radio station will love to
pay less for less used bandwidth. In the end, people might think that
good old FM radio sounds actually better than most DAB stations, and...)
If you include the capability to offer surround/3D audio transmission,
DAB+ would offer "something more" than FM. You could say this would
present some real advantage, especially if you see how many people
listen to radio via headphones. Radio stations have experimented with
UHJ, Stereo Surround, Dolby Digital and (parametric) Mpeg Surround, the
most recent attempt to transmit surround sound via terrestrial radio.
I am modest enough to state that the UHJ/AAC proposal is actually better
than anything else above... thanks to the combined power of modern audio
codecs (DAB+ uses HE-AAC) and UHJ/LRTQ!
(This was just a bit of the necessary PR work, for the lurking radio
broadcasters on this list which might have to convince some bean
counters... Why should you invest some money and actually some time
into anything < at all >? The "best" or most practical solution is
always if you - as a bean counter or actually manager - decide that some
idea doesn't have any merit, or is just not practical. Then you don't
have to work, which is a huge advantage! Philosophically speaking, this
is the principle of < least effort >. You have thought about something
in a thorough way and during a long time, but... Don't go there! In
fact, close the case, and archive the project and recordings
somewhere... :-) This is of course how things should < not > be.
End of the small philosophical investigation.)
I am aware that a lot of radio transmission/reception happens
(nowadays) via Internet transmission. This form of radio broadcast
belongs also to the area of Internet streaming, which I did mention.
-THJ (3 channel) should only be used if the original material is three
channel
-PHJ (4 channel) is preferred
Yes, but only if you have some real 3D audio recording, which means the
Z channel is not empty.
It would need some neat little standalone UHJ->-B-format decoders writing ...
(But that _could_ (unideally) progress whilst people beenfitted from just
L/R.)
Anyone able to comment on why the UHJ (2 channel) buttons on Ambisonia
were (?)never made active?
If you can offer the real thing (3- or 4-channel Ambisonics) within the
current transmission channels/frameworks, forget about 2-channel UHJ.
(Which had been developped to fit Ambisonic/surround transmission into
the then existing analogue distribution models, which were all 2-channel
based.)
The 2.5/SHJ variant was an experiment by the broadcasters which didn't
make it to many if any radio listeners. (The existing SHJ decoders were
probably bought only by the radio stations/broadcasters themselves. I
actually have < never> heard of any UHJ decoder capable to decode
more than 2 channels. In our case we don't have the problem to install a
base of analogue decoders, because we definitively talk about some
decoder programs/apps, i.e. software. Any UHJ decoder software should be
able to decode BHJ, but IMO mainly for "legacy reasons". Add THJ and
PHJ, as new standard case. As Michael writes, you would "transcode" UHJ
to B format, so to WXYZ presentation. And some smartphone app would have
to decode this to some binaural representation. To state the obvious: We
would use UHJ/LRQT just because to become backward-compatible to stereo.
And we transmit B format over < extended LR stereo >, including one or
two additional audio streams. Which from the perspective of existing
file and/or container formats might be labeled as < extension data
streams >.)
II
Yes, we are hitting our head on the ceiling with FuMa.
Personally, though, if we are to move on I would go for an infinite order
'file' format.
Otherwise before our bruised heads recover we will be banging the ceiling
again ....
But it needs doing.
Michael
This is some real argument, if an extension of .AMB (".AMB+") to 4th
order is not really feasible or practical.
("Infinite" formats can lead to implementation errors/issues, so maybe <
some > restrictions still makes some significant sense? You can also
define format "profiles", as the Mpeg does. "Up to 4th order, up to 7th
order, up to 99th order"...)
Thanks for your contribution, any discussion needs at least two people...
Stefan
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