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List Info Thread: : r613 - docs/nutissues.txt
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: r613 - docs/nutissues.txt |
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List Info Thread: : r613 - docs/nutissues.txt
[1-10] [11-14]
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gmx.at> writes:
>> >> >> > > On a related subject,
it might also be useful to define
>> >> >> > > the channel disposition
when there is more than one. Mono
>> >> >> > > and stereo can go by
with the classical default, but as
>> >> >> > > soon as there is more
channels it is really unclear. And
>> >> >> > > imho such info could
still be usefull with 1 or 2
>> >> >> > > channels. Something
like the position of each channel in
>> >> >> > > polar coordinate (2D or
3D?) should be enouth.
>> >> >> >
>> >> >> > I agree
>> >> >> > What about that LFE channel
thing?
>> >> >>
>> >> >> I was thinking about simply
setting the distance to 0,
>> >> >> however a flag for
"non-directional" channels might be
>> >> >> better.
>> >> >
>> >> > This is wrong, LFE is not about
direction but about the type
>> >> > of speaker. LFE stands for
"Low-frequency effects". If id
>> >> > move a other random speaker at
disatnce 0 and the LFE one out
>> >> > and switch channels it wont sound
correct ...
>> >> >
>> >> >>
>> >> >> > And where do we put this
info, The stream header seems the logic
>> >> >> > place if you ask me ...
>> >> >>
>> >> >> I agree, this is essential
information for proper presentation it
>> >> >> definitly belong there.
>> >> >
>> >> > Good, now we just need to agree on
some half sane way to store it.
>> >> > for(i=0; i<num_channels; i++){
>> >> > x_position s
>> >> > y_position s
>> >> > z_position s
>> >> > channel_flags v
>> >> > }
>> >> >
>> >> > CHANNEL_FLAG_LFE 1
>> >> >
>> >> > seems ok?
>> >>
>> >> I'm not convinced this is the right way to
go. Consider a recording
>> >> made with several directional microphones
in the same location. Using
>> >> spherical coordinates could be a
solution.
>> >
>> > The above was intended to specify the location
of the speakers not
>> > microphones.
>>
>> I'm having a hard time imagining a player moving my
speakers around
>> depending on the file being played.
>>
>> > And spherical coordinates would just drop the
distance, thats the same
>> > as setting the distance to 1 and storing that
as xyz.
>>
>> Spherical coordinates without radius needs only two
fields.
>
> True, but that gets tricky with integers and
precission.
Use rational numbers. That's essentially what you suggest
below anyway.
>> > Actually the main reason why i didnt use
spherical is that with integers
>> > theres a precission to decide on or you end up
with rationals. And this
>> > somehow starts looking messy ...
>>
>> I don't see any fundamental difference. If
restricted to integer
>> coordinates, an arbitrary point can be described
only with a certain
>> precision, regardless of coordinate system.
>
> True but if you map the points to a sphere, then x,y,z
gives you arbitrary
> precisson on the surface of the sphere while with
spherical coordinates
> this needs some additional "tricks".
> Thus x,y,z give you arbitrary directional precission at
quite low complexity.
I didn't realise you were only interested in direction. Not
that I
know what you'd use the distance for, or how.
>> >> Whatever the coordinate system, the
location and orientation of the
>> >> listener must be specified, even if there
is only one logical choice.
>> >
>> > of course
>> > right_position s
>> > forward_position s
>> > up_position s
>> >
>> > And
>> > "the listener is at (0,0,0), (1,0,0) is
right, (0,1,0) is forward,
>> > (0,0,1) is up"
>>
>> You're forgetting the measurement unit, i.e.
metres, feet, etc.
>
> Hmm, I was thinking that only x/y, x/z that is the
direction would matter.
> If theres some sense in also storing distance then we
would need a 4th
> variable to specifiy the precission like:
> (x/p, y/p, z/p) meter
>
> We can surely do this if someone thinks this is
usefull.
I don't think it's useful, but there's no telling what
people who
measure the copper purity of their speaker cables might
believe.
--
Måns Rullgård
mans
However I
doubt that real world units would be useful here.
Even if one want to make some adjustement to better match
the playback
system, simply having the distances relative to one of the
speaker
should be enouth.
Albeu
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