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View Poll Results: Which samples sound (A or B) better, when decoded with certified DPLII deocers
Clips A sound better 0 0%
Clips B sound better 5 83.33%
Both sound the same 1 16.67%
Voters: 6. You may not vote on this poll

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Old 7th June 2006, 08:33   #1  |  Link
3dsnar
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Dolby Pro Logic II encoding test (90 vs 180 phase shift)

Here are two clips,
http://forum.videohelp.com/images/gu...165/180vs90.7z

And the reference (original 6 channel input) clip.
http://forum.videohelp.com/images/gu...helem_6chnl.7z

Each downmixed with:
Lt = FL{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.866 SL{180} + 0.5 SR{180}
Rt = FR{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.5 SL{0} + 0.866 SR{0}
and
Lt = FL{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.866 SL{90} + 0.5 SR{-90}
Rt = FR{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.5 SL{-90} + 0.866 SR{+90}

Please test them with your dolby certified decoders
and decide which ones sounds better (eg. A vs B version) with reference to the original sound.
The poll question is related to fifthelem_A.mp3 and fifthelem_B.mp3,
while speech_A.mp3 and speech_B.mp3 should sound identical
(to see that both downmixing methods are compatible with DPLII decoders)
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Old 7th June 2006, 14:17   #2  |  Link
scharfis_brain
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I cannot tell for sure (tendency goes to clip A) which is the 180 or 90 degree clip because I curently have no possibility to play back the AC3 in direct 5.1 off my PC.

but anyways this is NOT a fair comparision.

fair would have been:

Each downmixed with:
Lt = FL{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.866 SL{180} + 0.5 SR{180}
Rt = FR{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.5 SL{0} + 0.866 SR{0}
and
Lt = FL{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.866 SL{+90} + 0.5 SR{+90}
Rt = FR{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.5 SL{-90} + 0.866 SR{-90}

or Rockarias style:

Lt = FL{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.866 SL{0} + 0.5 SR{180}
Rt = FR{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.5 SL{180} + 0.866 SR{0}
and
Lt = FL{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.866 SL{+90} + 0.5 SR{-90}
Rt = FR{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.5 SL{-90} + 0.866 SR{+90}

but you are testing two types of four concurring types.
the traditional mixing with 180
and rockarias inverse mixing with 90

And I think this is perfectly audible when you can hear "weapons loaded" at the very beginning of the sample.

sample A lets it sound from the center.
sample B lets it sound from the surround.

But this is not due to the different phases but more due to the reason that one of the surround channels (in relation to each other) become inverted with your 90 matrix. (IMO)

(this is the thing I always tried to explain as center surround issue to Rockaria. But it seems to be a slightly different effect here)

so would you redo the samples, please?
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Last edited by scharfis_brain; 7th June 2006 at 14:21.
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Old 7th June 2006, 15:02   #3  |  Link
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http://forum.doom9.org/showpost.php?...1&postcount=42
Quote:
Originally Posted by scharfis
IMO this matrix is useless.
Just imagine the MonoSurround-condition: Rear left and rear right are carrying the same signal.
With this matrix you'll succesfully eliminate the mono surround out of the downmix.
This means to me, that
Code:
Dolby Pro Logic Left   Right   Center Rear Left Rear Right 
Left Total        1.000 0.000  0.7071  0.866     -0.5 
Right Total      0.000 1.000  0.7071  -0.5        0.866
is a derivation from the faulty matrix above and should not be used.
You may experience wider sounding surround channels, because every middle information (mono information) is weakened in the surround downmix.
Quote:
Originally Posted by scharfis
or Rockarias style:

Lt = FL{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.866 SL{0} + 0.5 SR{180}
Rt = FR{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.5 SL{180} + 0.866 SR{0}
and
Lt = FL{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.866 SL{+90} + 0.5 SR{-90}
Rt = FR{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.5 SL{-90} + 0.866 SR{+90}

but you are testing two types of four concurring types.
the traditional mixing with 180
and rockarias inverse mixing with 90


(this is the thing I always tried to explain as center surround issue to Rockaria. But it seems to be a slightly different effect here)
Quote:
Originally Posted by scharfis
I found, that Rockaria's personal matrix has problems with centered surround effects that are meant to be reproduced by both surround speakers (DPLII) or the surround-back speaker (DPLIIx).
Inverting the phase of one of the Surround channels like this modified matrix does can enhance the perceived width and separation of both channel because it is simply something like crosstalk reduction. But At the cost of centered surround sounds. That's why I prefer the unaltered matrix.
.....
....

@scharfis, do you see your posts are 'arbitrary itself' ?
Would you stop posting against anybody with no basis & no understanding at all? That does not help anything.

traditional mixing with 180 :: what the traditional means? your myths?, your Gods' words?
inverse mixing with 90 : youself admitted you have no clear picture of the DPL II model already?
If you continue posting like this, I will regard them as personal attacks, only to depreciate any resonable conversations.
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Old 7th June 2006, 15:23   #4  |  Link
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I don't see a contradiction to myself here. I think that these quotes still enhance the statements of my first post in this thread.
Also it is not a personal attack as I said many times in past, too.
If you are interpreting my answers as personal attacks it is your problem. Not mine!

Quote:
traditional mixing with 180 :: what the traditional means? your myths?, your Gods' words?
The wikipedia style of matrix. The Besweet style of matrix. The AC3filter style of matrix. The ffdshow style of matrix. Is this enough traditional style?

Quote:
inverse mixing with 90 : youself admitted you have no clear picture of the DPL II model already?
Of course not, as I already did some manual mixes myself, build some active Dolby surround mixing ciruits etc.

If you should find irony in the last sentence, keep it for yourself. Thanks.

Actually I think you are the person that is not able or willing to do a objective conversation without personal attacks.
I never did attack you. But you do!
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Old 7th June 2006, 19:03   #5  |  Link
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Test with a SONY STR-DE495 receiver, DPL II Movie mode.

There are a clear difference between A and B in "weapons loaded" (?) and "Yes, Sir" (3 sec.).
There are presents in FL, FR, BL, BR original audio, and not at Center channel.
In A "Yes, Sir" is basically only at Center channel.
In B "Yes, Sir" is present in all five channels, then is not perfect but better than A.
Then my vote for B.

I tried also a C option (matrix 3 from original thread) with indistinguishable differences with B (at least for my ears).

Last edited by tebasuna51; 7th June 2006 at 19:17.
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Old 7th June 2006, 19:10   #6  |  Link
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@scharfis, I am pretty much impressed by your convenient logic adaptible to any situations.

In my previous quotes :

The contradiction in the 1st and 3rd quoted messages from you looks to me clearly an irony. (and the 2nd one just a justification)

The 'inverse 90 degree' is actually the +-90 degree phase shifts, to be correct, based on my best reasoning & understaning which describes the DPL II model from Dolby's unclear documents.

Look at the 1st quote.
Now do you distinguish which is useless? : my useless model vs your invaluable objections

scharfis, I just want you not to play with my id at all.

@3dsnar,
The two fifth_elm clips showed a distinct difference in the first part, the _b clip sounded some wider fronts
But I have no idea which is with better seperation fidelity without the original 6ch clip(in any form such as mp4) as I mentioned in other thread.

[edit] Yeah, I see tebasuna has the same opinion.
Now with the original 6ch AC3, I see the fifth_elm_B has the better seperation fidelity. voted.
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Old 8th June 2006, 08:41   #7  |  Link
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OK, thanks all of you for votes.
BTW. The original signal is provided too.

Yes, B is 180 deg phase shift (the simpler approach),
A is 90 deg. phase shift.

The sign variations are not important, because they result
in phase invertion in the decoded signal and do not affect the separation (as Tebasuna already noticed). Therefore A and B are enough to distinguish between 90 and 180 phase shifts.
I agree with Scharfis that the 90 deg phase shift should have been prepared with the same sign style, to be fully consistent with the 180 deg. shift. Maybe next time

(early) conclusions.
1) There is a noticable difference between the 90 deg phase shift and 180 deg phase shift
2) 90 deg seem to produce significantly worst results, thus probably the DPLII downmixing equation is based on 180 deg. shifts (simple sign change).

---

BTW. Please test Aud-X DSfilter DPLII decoder (or rather DPLII decoder simulation),
by sending the output as AC3 through SPDIF to your HT amps.
I am curious of your opinions and especially your thoughts regarding its quality vs certified dolby decoders quality

3d
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Old 8th June 2006, 09:39   #8  |  Link
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Quote:
Originally Posted by 3dsnar
OK, thanks all of you for votes.
BTW. The original signal is provided too.
But after my post in other thread, without any notice or acknowledgement.
http://forum.doom9.org/showpost.php?...9&postcount=63
Quote:
You might want to add two more models to fully reflect the discussions in the related threads:
Lt = FL{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.866 BL{-90} + 0.5 BR{-90}
Rt = FR{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.5 BL{90} + 0.866 BR{90}
and
Lt = FL{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.866 SL{180} + 0.5 SR{0}
Rt = FR{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.5 SL{0} + 0.866 SR{180}
...
You might also want to test with original 6ch(mp4 format) vs dpl II mix(music + speaker test clip), to compare reasonably.
The FFDShow can switch between PCM/AC3 in digital out mode on the fly making it easy to compare.
As I said many times, the speaker test clip is most generous on any models(more than 95% of the seperation quality).

Also the matrices values(Ls1,Ls2,Rs1,Rs2....) might affect the seperation quality by the phase shift degree change.
Comparing the Wikipedia matrix with the current one would be reasonable(also making it reasonable using the variable reference than the values).

So far, the fifthelem_B showed noticeable better seperation, but the test is not setup to compare the seperation fidelity(original vs DPL II).
Quote:
Originally Posted by 3dsnar
Yes, A is 180 deg phase shift (the simpler approach),
B is 90 deg. phase shift.
Can you provide the proof in a source format(no dll)?
Quote:
Originally Posted by 3dsnar
The sign variations are not important, because they result
in phase invertion in the decoded signal and do not affect the separation (as Tebasuna already noticed). Therefore A and B are enough to distinguish between 90 and 180 phase shifts.
Again, it's just your very dangerouse assumption.
You can test it with FFDShow which can adjust the matrix value with the sign.
It shows no difference only with the simplest speaker test file.
Also prove exactly which Tebasuna's observations concure your assumptions.

Quote:
Originally Posted by 3dsnar
I agree with Scharfis that the 90 deg phase shift should have been prepared with the same sign style, to be fully consistent with the 180 deg. shift. Maybe next time
also check my quote above. indeed, the polls feels like something public.
Quote:
Originally Posted by 3dsnar
(early) conclusions.
1) There is a noticable difference between the 90 deg phase shift and 180 deg phase shift : agreed.
2) 90 deg seem to produce significantly worst results, thus probably the DPLII downmixing equation is based on 180 deg. shifts (simple sign change).
I agree again we are using totally differernt languages. Apparently it seems what you wanna see.
---
Quote:
Originally Posted by 3dsnar
BTW. Please test Aud-X DSfilter DPLII decoder (or rather DPLII decoder simulation),
by sending the output as AC3 through SPDIF to your HT amps.
I am curious of your opinions and especially your thoughts regarding its quality vs certified dolby decoders quality
My independant Ad. :
Sorry, unfortunately, I am very much satisfied with the FFDShow with probably 1000% of proven better features and stability.
I also believe they will provide the DPL II encoding with 90 deg. phase shift very soon(with current adjustable matrix).
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Old 8th June 2006, 09:51   #9  |  Link
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Was it a blind test to fool people by an anonymous person?
Quote:
Originally Posted by 3dsnar original in the poll description
Here are two clips,
http://forum.videohelp.com/images/gu...165/180vs90.7z

And the reference (original 6 channel input) clip.
http://forum.videohelp.com/images/gu...helem_6chnl.7z

Each downmixed with:
Lt = FL{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.866 SL{180} + 0.5 SR{180}
Rt = FR{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.5 SL{0} + 0.866 SR{0}
and
Lt = FL{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.866 SL{90} + 0.5 SR{-90}
Rt = FR{0} + 0.7071 C{0} + 0.7071 LFE{0} + 0.5 SL{-90} + 0.866 SR{+90}
Quote:
Originally Posted by 3dsnar that I captured just after his conclusion
Yes, A is 180 deg phase shift (the simpler approach),
B is 90 deg. phase shift.
Quote:
Originally Posted by 3dsnar what you are seeing now
Yes, B is 180 deg phase shift (the simpler approach),
A is 90 deg. phase shift.
You definitely need to provide the encoding source of your test poll.
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Old 8th June 2006, 10:18   #10  |  Link
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I have informed you of the input included (after you suggested so).
You should read my posts more carefully.
-----------
I am asking to verify my DPLII simmulation decoding algorithm,
not the entire DSfilter.
-----------
Here is the matlab code that I used for downmixing.

function [y, y2]=DPLIIdownmix(s)

FL=s(:,1);
FR=s(:,2);
C=s(:,3);
LFE=s(:,4);
SL=s(:,5);
SR=s(:,6);

y=zeros(length(FL),2)
y2=zeros(length(FL),2);

wgF=1;
wgC=sqrt(0.5);
wgA=sqrt(0.75);
wgB=sqrt(0.25);

Nrm=wgF + wgC + wgC + wgA + wgB;
wgF=wgF/Nrm;
wgC=wgC/Nrm;
wgA=wgA/Nrm;
wgB=wgB/Nrm;


%180 deg phase shifts
y(:,1) = FL*wgF + C*wgC + LFE*wgC - wgA*SL - wgB*SR;
y(:,2) = FR*wgF + C*wgC + LFE*wgC + wgB*SL + wgA*SR;


%90 deg phase shifts
y2(:,1) = FL*wgF + C*wgC + LFE*wgC + wgA*imag(hilbert(SL)) - wgB*imag(hilbert(SR));
y2(:,2) = FR*wgF + C*wgC + LFE*wgC - wgB*imag(hilbert(SL)) + wgA*imag(hilbert(SR));
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Old 8th June 2006, 10:31   #11  |  Link
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Quote:
Originally Posted by 3dsnar
I have informed you of the input included (after you suggested so).
You should read my posts more carefully.
Now I see at the last part....
So you feel OK performing the blind test poll without any prior permission?
Anyway, I want to believe it can be forgiven if the test routine proves used correctly.

Anybody know where I can get the matlab?
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Old 8th June 2006, 10:55   #12  |  Link
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Quote:
Originally Posted by Rockaria
So you feel OK performing the blind test poll without any prior permission?
Yes
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Old 8th June 2006, 11:00   #13  |  Link
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Quote:
Originally Posted by 3dsnar
BTW. Please test Aud-X DSfilter DPLII decoder (or rather DPLII decoder simulation),
by sending the output as AC3 through SPDIF to your HT amps.
I am curious of your opinions and especially your thoughts regarding its quality vs certified dolby decoders quality
Sorry, I have attached my PC to a old amp with only stereo input (with DPL I capability).

To test 5.1 or DPL II I need to burn a CD and go to other room with a DVD/DivX/mp3 player attached to the SONY receiver.

I tried, to make some kind of test, use your Aud-X DSF in GraphEdit but don't accept WAVDEST or DUMP output. Only accept DirectSound output (like you say in other thread).

For my configuration your Aud-X DSF is unusable.
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Old 8th June 2006, 11:17   #14  |  Link
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@3dsnar, you seem to be very confident about ...what?
Anyway, I myself won't engage in such flip-flop games any more.

http://en.wikipedia.org/wiki/MATLAB : something that costs money for what I do not owe.
http://en.wikipedia.org/wiki/Hilbert_transform : seems to be the logic for transforming a square wave form to a strange curve with 90 deg. phase shifts

Possibly we can find the corresponding function in any forms of avisynth/sox plugin..
It's gonna take a long while to prepare the verification test.... oh well, nothing to believe.

It seems it has just lengthened the route further, forcing me to continue my own approach.
At least, I believe I have proved the reference model 4 better than 2 practically, and 1/3 better than 2/4 theoretically. period.

/fooled
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Old 8th June 2006, 11:37   #15  |  Link
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You can believe the test, or not.
You can prepare your own downmixes as well.
Freedom of choice.
-------
Hilbert transform shifts all of the signal (represented as Fourier series) sinusoidal components by Pi/2 (90 deg). Hence, such operation may result in waveform change.

Due to long discussions related to creating DPLII downmixes,
and especially 90 dg. vs 180 dg. phase shift myths and speculations, I hope the test has its value for reasonable people.
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Old 8th June 2006, 17:32   #16  |  Link
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Quote:
Originally Posted by 3dsnar
Freedom of choice.
Oh yeah, my favorest word! But when abused it becomes what we have just experienced.

So you are proud of playing with the POLL!
Do you even realize you abused the public POLL for your personal purpose?
Also do you understand I tried my best to prevent this kind of misleading, in the first post in other thread about your POLL?
http://forum.doom9.org/showpost.php?...9&postcount=63

What I am doubting most is the ethic of an anonymous identity, who wants to move people dramitically with minimum honest efforts.

For an example, your faulty DSFilter unable to connect the out pin to other filters is what I pointed out 5 month ago, still not fixed.
Your gesture is something like identifying the bugs with all the smooth generic promising words, but in fact no honest consideration & fix at all. That's why I can't trust yours at all to be honest, including all the other hidden invaluable un-disclosable know-wheres(no know-hows).
Your 'DPL II decoder' is another good example of the misleading. aud-x? .oh well..I forgot it..
Why don't you just put more time to fix the bugs silently in the one-person-owned-WE .com, for your future, instead of playing the waste games?

Even if I become to verify by myself your doubtful process and result, there's no doubt you just(afterall) created the minimum result(who knows if it's even intented mystypings) that you wanna see in a very deceiving way and you seem to be satisfied you proved something, moved people, realizing no ethical & logical problem at all. Another perfect example of Public Misleading.

I believe you will have to ACTIVELY prove your QUESTIONED HONESTY with proper perfectly OPEN processes and full considerations as I described in other thread, realizing you just created a bigger problem.
Until then, I believe all the other issues are none of your concern.

Thanks anyway for your little event(a true surprise never experienced before) that makes me think of something very different.
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Old 8th June 2006, 18:40   #17  |  Link
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IMHO you've got a serious problem man.
Sorry, but conversation with you is waste of time.

And I am probably not alone with this sad conclusion.
This is the last time I replied to your attacks.
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Old 8th June 2006, 18:45   #18  |  Link
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Will see.
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Old 9th June 2006, 04:26   #19  |  Link
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Well, I don't have the matlab, nor could find a corresponding plugin for avisynth yet.
Which is why I want to share my idea looking for positive contributions from anybody talented and equipped.
Below is my draft plan to figure out the closest DPL II model for s/w emulations, possibly in a very OPEN, independant, objective, fair and fully reflected but economic way.

Now some more tests are included such as 'the verification of the Hilbert() algo' as well as many other essential considerations to go through the proper approach & procedure.
If the minimum test environment is not setup soon, I am going to add the results in my original thread when available.

1. prepare proper tools & organize the test.
. s/w tools : matlab or avisynth/sox with proper plugin(esp. for 90 deg phase shift)
. resource orgarnizer : an independant user with proper DPL II understanding, s/w tools, h/w equips, resources.
. refined model : the orgarnizer refines the test procedures & models
. prepare, test, report and share the results

2. prepare a 6ch mixed original source for full channel complexity and easy identification
The DPL II encoding with avisynth is listed in the below thread.(for models m12, m22)
http://forum.doom9.org/showpost.php?...0&postcount=82
<avs 6ch clips mixing example>
spk=DirectShowSource("SSWAV06.m4a")
muz=DirectShowSource("6chmusic.m4a")
...
mxx=MixAudio(spk, muz, 0.4, 1)
..
dpl2Enc(mxx, 0.7071, 0.7071, 0.866, -0.5, -0.5, 0.866)
...

3. identify the weights of orginal matrices : including the coefficients on rears to be shared on each channel, with no phase shifts(passive)
Code:
<mxA> : widely used for s/w encoding
DPL II   Lf      Rf      C        Ls      Rs 
Lt        1.000 0.000  0.7071  0.866    0.5 
Rt        0.000 1.000  0.7071  0.5      0.866 

<mxB> : Wikipedia one, possibly from Dolby
DPL II   Lf      Rf      C        Ls      Rs 
Lt        1.000 0.000  0.707   0.8165   0.5774 
Rt        0.000 1.000  0.707   0.5774   0.8165
4. identify target DPL II models(formula) to compare
<m11>
Lt = mix(Lf.0, C.0, Ls1.-90, Rs2.-90) == mix(mix(Lf, C), mix(Ls1, Rs2).-90)
Rt = mix(Rf.0, C.0, Ls2.+90, Rs1.+90) == mix(mix(Lf, C), mix(Ls2, Rs1).+90)
<m12> rears(m11).-90
Lt = mix(Lf.0, C.0, Ls1.-180, Rs2.-180) == mix(mix(Lf, C),-mix(Ls1, Rs2))
Rt = mix(Rf.0., C.0., Ls2.0, Rs1.0} == mix(Rf, C, Ls2, Rs1)
<m13> m11.-90 == m11?
Lt = mix(Lf.-90, C.-90, Ls1.-180, Rs2.-180) == mix(mix(Lf, C).-90,-mix(Ls1, Rs2))
Rt = mix(Rf.-90, C.-90, Ls2.0, Rs1.0) == mix(mix(Rf, C).-90, mix(Ls2, Rs1))
...
<m21>
Lt = mix(Lf.0, C.0, Ls1.+90, Rs2.-90) == mix(mix(Lf, C), Ls1.+90, Rs2.-90)
Rt = mix(Rf.0, C.0, Ls2.-90, Rs1.+90) == mix(mix(Rf, C), Ls2.-90, Rs1.+90)
<m22> rears(m21).-90
Lt = mix(Lf.0, C.0, Ls1.0, Rs2.-180) == mix(mix(Lf, C, Ls1),-Rs2)
Rt = mix(Rf.0, C.0, Ls2.-180, Rs1.0) == mix(mix(Rf, C, Rs1),-Ls2)
...

When -180 = -, +90 = Hilbert(), -90 = -180.+90 = -.+90

5. perform the verification of Hilbert() algo if any useful, with m12 * mxA
<m12>
Lt = mix(Lf.0, C.0, Ls1.-180, Rs2.-180) == mix(mix(Lf, C), -mix(Ls1, Rs2)})
Rt = mix(Rf.0, C.0, Ls2.0, Rs1.0) == mix(Rf, C, Ls2, Rs1)
<-180 = -(+90.+90) == -Hilbert().Hilbert()>
Lt = mix(Lf.0, C.0, Ls1.-90.-90, Rs2.-90.-90 == mix(mix(Lf, C), -mix(Ls1, Rs2).+90.+90)
Rt = mix(Rf.0, C.0, Ls2.0, Rs1.0)

6. verify if m13 == m11 with mxA
.discard m13 if identical or refine the 'phase shift' concept

7. verify if different phase shift degrees makes any difference with (m11, m12) * mxA
.discard the worse model

8. prepare & perform the seperation fidelity comparison with remaining candidates combination(matrices, models)
m11 * mxA : <reference1>
m11 * mxB :
m12 * mxA : <reference2>
m13 * mxA :

m21 * mxA : <reference3>
m21 * mxB :
m22 * mxA : <reference4>

9. conclusions
. the test orgarnizer share & report the test results
. users evaluate & verify the results(polls and/or posts)

Thanks,
__________________
u know everything in the end, or now if aligned... no right(x).right(y) pls. it's confusing... : phase-shift /Jun.2006
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Old 9th June 2006, 13:39   #20  |  Link
ursamtl
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Join Date: May 2004
Location: Montreal
Posts: 729
If you have Plogue Bidule, why don't you just model the Dolby encoding using it? Bidule has a built-in Hilbert Transform filter (although in my experiments, it seems to produce a -90 phase shift, so for the +90 shift, you'll need to invert the signal). Another option for the Hilbert is to use Christian Budde's excellent Phasebug VST plugin (freeware). This gives you the possibility of any phase shift in a 360 circle.

If you don't have Plogue Bidule, try Audomulch.

I haven't done much with DPLII since I've never been impressed with its results, but I can tell you that in my experiments with Ambisonics, the 90 phase shift used in some encoding designs is essential. For example, in the superstereo circuits I've modelled using Plogue Bidule and Phasebug, the 90 phase shift balances the ambience nicely across the surround speakers, but moving it to 0 or 180 forces the ambience all to one surround speaker on another. Again, the application is different from DPL, but I've read a lot of surround sound documentation over the past couple of years and the Hilbert Transform is everywhere!

Finally, I know you guys are passionate about your points of view, but let's relax and enjoy this experimentation.

Regards,
Steve.
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