New Handling of delayline and fractional delay #50

fietew · 2016-01-11T15:41:41Z

Introduces delayline_write and delayline_read as an alternative to delayline. This allows to split the handling of fractional delays into a pre- and post-processing stage. During delayline_write the data may be oversampled and stored with the new sampling rate in order to reuse the oversampled signal for different delays in delayline_read.
A second technique, called the Farrow-Structure, is implemented. It allows delayline_write to pre-process the data with a parallel filter structure and stores the outputs in an interleaved manner. Individual delays are applied to the data using the Horner-scheme.

TODOs:

extent usage to all sfs functions
adjust documentation and source code comments
support of single channel signal with multiple delays and weights

… cardinalis

Conflicts: SFS_general/general_least_squares.m

hagenw · 2016-01-12T09:25:04Z

Interesting, I guess the goal behind this is to save some time, especially for local WFS?
For a better understanding it would be nice if you could as a next step update the function headers of delayline_write() and delayline_read(), so far I'm not completely sure what they are doing.

In some driving functions you replaced the old call to delayline() with a combination of the two new commands. Where is the advantage, does Matlab use better automatic caching in this case?

Two comments regarding the code:

it is not a good idea to use the variable delayline as we have also the function delayline(), or will the function be removed at the end?
delayline(), delayline_read(), and delayline_write() share a lot of common code. As I'm not completely sure how it works, I have no direct proposal how to fix this, but we should consider it.

fietew · 2016-01-12T14:07:18Z

Yes, there is a significant overhead in the delayline procedure especially for the "resample" method. The reasons for splitting the two functions are:

better mapping of the pre- and post-processing onto the code structure
re-using the pre-processed signal in different function calls of delayline_read()

Regarding your comments:

the function delayline() should be removed in the end
I agree. The problem is mainly related to the farrow structure. Basically every type of fractional delay filter, which is can be designed for the post processing stage delayline_write(), has to be designed in pre-processing stage if the farrow structure is used. Simply speaking, some of the stuff of post-processing stage is shifted to the pre-processing stage if the farrow structure is used.

hagenw · 2016-01-12T14:20:15Z

OK, I see.

One question: as a normal user I don't care and I'm happy that it is faster now. Should we maybe still have the function delayline() and include that one into the driving functions to increase readability of the code. Inside delayline() we then simply call delayline_write() and delayline_read() as you do at the moment inside the driving function.

…ssues

fietew · 2016-01-22T09:15:40Z

I will merge the two functions delayline_write() and delayline_read back together, as it turned out to be less efficient than I thought.

hagenw · 2016-02-01T15:47:07Z

What is the status of this?
I see you have added new methods to delayline(), but also a new way of dealing with the configuration, that is not transparent to me. In SFS_config.m there seems to be no change and we still have:

% use fractional delays for delay lines
conf.usefracdelay = false; % boolean
conf.fracdelay_method = 'resample'; % string

In delayline() we have now conf.fracdelay.pre.method in addition. Is this mandatory to have, or only used in some cases? The indention in the help message seems to be broken, so it is not possible to say what will happen ;)

The farrow is also not implemented yet. Should I wait with the merge until you have that ready, or just force you to clean up the configuration settings and then merge it?

fietew · 2016-02-01T20:02:19Z

SFS_config.m is not up-to-date. I'll have to fix that.

Actually the indention is correct, as it should point out, which entry of the conf is used, if a particular condition is fulfilled. Any suggestions to make that clearer are welcome.

farrow will be implemented in the near future. However, a merge could be done beforehand.

hagenw · 2016-02-01T23:06:44Z

OK, in the meantime I was able to understand the help entry. I will try to update it in order to make it easier to understand. I will wait until you have updated SFS_config.m and start testing and merging the code afterwards.

Before testing I would also like to ask a few more questions:

1.) In the old code, there was an if test if we should use fracdelay at all. This has vanished in the new version and we always perform the specified fracdelay.pre.method and fracdelay.filter. Is there a reason behind this or a bug?
It seems to be desired as there is the sig = buffer(1:rfactor:samples,:); entry at the end, but it requires also to specify a fracdelay.filter even if you would like to use only integer delays, which could seem strange to a user.

2.) In the old code there was a handling of the case that a common weight, delay is given for more than one channel. This is removed in the new version, will it still work?

3.) The purpose of the new code is still to avoid recursive calling of the delayline() function and speed up the processing for fractional delays? This is fine with me, but I would add the requirement that integer delay processing should be as fast as before.

fietew · 2016-02-17T13:36:24Z

Regarding your questions:
1.) The preprocessing method can be disabled by fracdelay.pre.method = 'none' and fracdelay.filter = 'zoh' is the integer delay. If it is desired to keep conf.usefracdelay, then I could set up an if clause to the set the filter and processing accordingly. (EDIT: config has been updated in 37c85d8)
2.) That's a bug. I will fix that. (EDIT: fixed with 82d1fc3)
3.) Beside the new if clauses and cases, there shouldn't be any additional overhead introduced to the integer delayline

hagenw · 2016-05-12T12:02:50Z

Could you make sure that the intention of code is always 4 and not 2 spaces.

fietew · 2016-05-13T07:42:28Z

Should I include the MIT license or will you do it during the merge?

fietew · 2016-05-18T12:36:45Z

I'm just saying, that it is not fully transparent what MATLAB's resample is doing. The documentation (http://de.mathworks.com/help/signal/ref/resample.html) is not easily accessible, either. I hence can't judge upon the correctness of this resampling method.

The "best" setting for fractional delay filters in the context of sound field synthesis is ongoing research.

* master: Fix dos line endings Update comments for SSR BRS

hagenw · 2016-05-18T19:24:50Z

OK, I agree and will include all settings and methods for resampling.

hagenw · 2016-05-18T19:26:44Z

I found the code of delayline() still very confusing, for example what is a preprocessing and postprocessing. In fc69b12 I did some restructuring and renaming of the conf settings, could you have a look at this and test if still everything is working as intended, please.

iseven() is used in time critical delayline(). isodd() is modified as well for symmetrical reasons

hagenw · 2016-05-19T17:48:05Z

SFS_general/lagrange_filter.m

+    end
+
+    li = zeros(Norder,Norder);
+    for idx=1:N


I guess instead of for idx=1:N you mean for idx=1:Norder?
As N is not defined before.

hagenw · 2016-05-19T17:50:39Z

In lagrange_filter() the actual fractional delays fdt are an optional argument. For me it is not clear what happens if you don't provide delays? As in the description it is stated that the function computes Lagrange interpolation filter for fractional delays, which seems meaningless if no delays are provided.

fietew · 2016-05-20T11:59:16Z

fixed

hagenw · 2016-05-20T12:28:15Z

Cool, indeed much shorter now ;)

hagenw · 2016-05-20T12:36:34Z

I found the code of delayline() still very confusing, for example what is a preprocessing and postprocessing. In fc69b12 I did some restructuring and renaming of the conf settings, could you have a look at this and test if still everything is working as intended, please.

Maybe this was not so well phrased.
What I did in fc69b12 was some rewriting of delayline() and the underlying conf settings. Could you have a look at it if I understood your desired behavior of delayline() correctly and it is still working in the direction you wanted it to work.

Beside this the only questions which remains is if we should ensure backward compatibility with the old conf settings used in earlier versions of the Toolbox. (Then my renaming of the conf settings in fc69b12 was maybe not the best idea.)
Backward compatibility seems to be important as delayline() is used in all time-domain and binaural simulation functions.

fietew · 2016-05-23T06:06:40Z

Seems okay to me

hagenw · 2016-05-23T13:45:13Z

I found it to messy to include backward compatibility code. In addition, the problem is relatively easy to fix by updating the conf settings. So I only included a exist('conf.usefracdelay','var') check with an error message. I hope this will not have to much impact on its performance.
As I have no Matlab this week, could you please run a last check comparing the performance for integer delays for the old implementation vs. this new one.

fietew · 2016-05-23T15:26:02Z

SFS_start;

conf = SFS_config;

sig = randn(2048, 1000);
dt = randn(1000,1);
w = randn(1000, 1);

tic;
for idx=1:100
  sig = delayline(sig, dt, w, conf);
end
toc;

delayline:

Elapsed time is 1.341628 seconds.

master:

Elapsed time is 1.301900 seconds.

hagenw · 2016-05-24T07:57:26Z

OK, perfect, this should be fast enough. And we will remove the check in a few month anyhow.

* master: Return delay offset from delayline() (#82) New Handling of delayline and fractional delay (#50) Fix dos line endings Conflicts: SFS_binaural_synthesis/auralize_ir.m SFS_binaural_synthesis/compensate_headphone.m

* master: Update copyright owner to SFS Toolbox Developers Update README for online documentation Remove wavread and wavwrite (#81) Return delay offset from delayline() (#82) New Handling of delayline and fractional delay (#50) Fix dos line endings Update comments for SSR BRS Update license in missing files Change license to MIT (#80) Make direction_vector() work with matrix => vector add modal weighting to time-domain nfchoa (#77) Fix comment of tapering_window() Add automatic scaling to loudspeaker weights for plotting (#78) Update comment of interpolation() Update NEWS Fix interpolation calling bug in interpolation_ir() Remove debugging parameter Fix normalization for 2D interpolation Further improvements to description of interpolation() Enhance description for interpolation() Conflicts: SFS_general/direction_vector.m

fietew · 2016-06-17T12:34:14Z

SFS_general/delayline.m

+        rfactor = delay.resamplingfactor;
+        a = [1 1 0 0];
+        f = [0.0 0.9/rfactor 1/rfactor 1.0];
+        b = firpm(delay.resamplingorder,f,a);


I don't remember how it got there, but having a fixed order for the filter design independent from the used resampling order is definitely a bad idea. I has to scale with the resampling factor.

Can you provide a fix for this?

Fiete Winter added 6 commits January 5, 2016 18:28

add new structure for delayline

2f933f6

some bugfixing and optimization of delayline

151362a

bug fixing

3eee690

fix problem with zero fractional delay due to implementation of sinus…

1902d65

… cardinalis

add thiran allpass filter + bugfixing

0f2fb7e

Merge branch 'master' into delayline

c027334

Conflicts: SFS_general/general_least_squares.m

update comments in src code

1dc9bf8

Fiete Winter added 4 commits January 12, 2016 17:57

fix bug in thiran filter coefficients

ef33081

add missing file lagrange polynomials

7a779ae

fix bug in lagrange filter

af3c82c

remove non-necessary/too complicated functionality and fix rounding i…

ebe490b

…ssues

merge delayline functions back together

1dc90a0

fietew mentioned this pull request Feb 17, 2016

Return wfs delay #62

Merged

Fiete Winter added 2 commits February 17, 2016 14:40

fix missing handling of single weight and delay

82d1fc3

fix config and test for delayline

37c85d8

hagenw mentioned this pull request Feb 17, 2016

Return delay values for time domain functions #64

Closed

Fiete Winter added 2 commits April 14, 2016 10:43

Merge branch 'master' into delayline

6caadda

fix bug related to Norder for zoh

2ada7a4

change indent from 2 to 4

190971a

Small changes to increase readability

16e9137

hagenw added 3 commits May 18, 2016 15:27

Merge branch 'master' into delayline

b00e4b9

* master: Fix dos line endings Update comments for SSR BRS

Code and comment clean up

4a91b31

Update structure of delayline and conf settings

fc69b12

hagenw added 2 commits May 19, 2016 19:40

Speedup iseven() and isodd()

60f8660

iseven() is used in time critical delayline(). isodd() is modified as well for symmetrical reasons

Code and comment cleanups

e00fd14

hagenw reviewed May 19, 2016
View reviewed changes

fix and shorten Lagrange filter

e916a28

fix broken legend

ac0745d

hagenw added 2 commits May 23, 2016 15:26

Add error message for old conf.usefracdelay setting

83cffbd

Update comment in SFS_config

a1865bb

Fiete Winter added 3 commits May 23, 2016 17:07

fix check for old delayline config

dc1bf7c

speed up delayline by checking for resampling factor

5a00433

fix missing semicolon

ea5644a

Update NEWS

c214af1

hagenw merged commit 7c6d484 into master May 24, 2016

hagenw deleted the delayline branch May 24, 2016 08:02

fietew reviewed Jun 17, 2016
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New Handling of delayline and fractional delay #50

New Handling of delayline and fractional delay #50

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New Handling of delayline and fractional delay #50

New Handling of delayline and fractional delay #50

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