KH wrote:
On 6/9/2012 2:09 PM, Gary Eickmeier wrote:
[...]
Stereo has nothing to do with HRTF.
As has been stated repeatedly. You asked "where did the recorded
ambiance go?". The answer is that the "ambience" is related directly to
the HRTF of the listener in the venue. Sans listener, there is *ONLY*
temporal and level data available for recording, and when recorded as
such, this data cannot subsequently be used to accurately reproduce
incident angle information. That information is lost in the translation.
That is a binaural, or head-related, process. With stereo, a field-type
system, we are reproducing the object itself in front of us and using our
own natural hearing mechanism and HRTF to listen to it.
Yes, that is the problem. The signal presented to the listener, in the
venue, has angular, temporal, and level clues that,
And phase as Audio Empire points out.
in conjunction with
the HRTF of the listener, create a spacial image. That information was
not, however, encoded into the recording except as temporal and level
information.
And possibly phase as well.
No matter how that information is played back, the signal
reaching the listener cannot be the same as in the venue.
It will never be the same, but that's not the point. The point is similar enough.
Reflecting
the sound cannot, except in the context of listener preference,
ameliorate this constraint.
It's not staright out prooven either way. But I'd say it's rather improbable.
But I'm open to be shown otherwise. That's why I wanted to see a theory not a
nice trick. Theory which would explain that the needed clues are in the
reproduced signal and distractions are either masked or attenuated enough.
snip
OK, here comes my main point of this whole discussion, my "closer."
We have discussed all of the audible parts of the listening experience in
the EEFs, What Can We Hear. We said that the spatial part is the main
stumbling block, the main difference between the reproduction and the
real
thing. Think of it as pure physics.
Feel free to present some, please.
If the spatial qualities I discussed are
audible, then we must make some attempt to reproduce them.
We can't reproduce them, they are not on the recording. What we can do
is to produce an illusion, the efficacy of which is clearly a function
of both engineering efficacy and listener preference.
Yes and no. It could be like Imax-3D -- it's illusion and in fact a simplistic
one -- but majority of people, those with proper binocular vision perceive the
effect.
The "real thing" comes to us as a primarily reverberant field from a
multiplicity of incident angles.
No, it does not, except in a narrow subset of live events.
Oh, in fact it does. In majority of live events it does. You got it wrong. In
your typical concert hall critical distance is about 4m-5m. In clubs and similar
small venues it's even closer. That means that even while one is sitting in a
first row the sound of further away instruments is dominated by reverberant sound.
Many times
the direct component (lets think of outside live events for example,
shall we?)
Outside events are allmost allways reinforced. So there goes that 'natural'
soundstage.
is the dominant component, and sometimes by wide margins.
Its very rare situation it's a dominant component and virtually never by a wide
margin.
[...]
and if the
recording really does contain some of the early reflected sound from the
venue,
It does contain it; translated into TEMPORAL and LEVEL information.
then it is more correct to reproduce that part of the sound by
reflecting it from the similar surfaces in your listening room.
You are not reflecting *that part of the sound*, you are reflecting ALL
of the sound, and in doing so, you reflect the DIRECT portion of the
signal as well. That is clearly inappropriate - it doesn't come to you
that way in the venue does it?
In fact does. It comes dominated by reverberation.
If the spacial is as important as you
maintain, then reflecting the direct portion of the signal is at least
as egregious an error as ignoring the reverberant part of the signal.
This is too simplistic.
In fact real properly[*] recorded events are miked at a distance closer than a
typical listener is. Moreover mikes are typically high in the air, so they get
early reflections primarily just from the floor and not from all the close
surroundings of typical listener (as there aren't any up there). Stereo
recordings recorderd from a typical listener position do not sound too
spectacularily. This is (partly) because that sound is then replayed at listener
venue where there are additional reflections (nobody listens in anechoic
chamber). So good recording already take into account those additional
reflections. Thus additional reflections are often 'unnatural' -- they contain
peaks due to room shape and dimensions (the incorporate replay room info), in
case of box speakers they are much damped in the highs, etc...
Gary's technique aims at getting those reflections right as I understand. But
what I miss is a physical and psychoaccoustical model of things, not an analogy
to mirrors. So this is not a theory it's just a trick. Theory should point out
which additions (due to the whole playback chain -- chain starting at the
recording) to the sound are benign and which are not, which help recreate the
illusion and which are standing in good illusions way. If for example some class
of reflections is benign then we might not care if ther are present or not. Is
some are troublesome then we know what should be dealt with.
[*] I'm speaking in the context of this thread -- propely here means rendering
nice deep audio scene in a listener room.
rgds
\SK
--
"Never underestimate the power of human stupidity" -- L. Lang
--
http://www.tajga.org -- (some photos from my travels)