[vlc-devel] [PATCH 1/2] audio_filter: SOFAlizer new module

Wolfgang Hrauda wolfgang.hrauda at gmx.at
Tue Apr 28 19:35:14 CEST 2015

Am 23.04.2015 um 19:37 schrieb David Fuhrmann <david.fuhrmann at gmail.com>:

> Hi,
>>>> ...
>>> This is not about how you implement the GUI. Even with one variable for the „current HRTF file", you can still implement a combo box in the GUI, for selecting predefined presets, instead of an open dialog.
>> I see. With one variable for the current HRTF file, how could the user change the "predefined presets" (i.e. selecting other files to compare between)?
>> For example:
>> Imagine I had my personal HRTFs measured and got two different files with different post-processing of the measurements. How would I (as a user) point SOFAlizer to them (e.g. in the settings) and then switch forth and back between them in the module's GUI (in your ideal implementation)?
> Well if they can be an arbitrary number of files, the best way is to manage a list of files as well. IIRC VLC also has the notion of a string list, but this might be a bit more complicated.
> I do not know these files so I don’t know how often it actually happens that you change the files or load more than three.

Usually, you would try out different files, when first using the module. Once you have settled to one, each user of the module would probably use their individual file and not switch very often.
You always use one file at once. So loading more than three files would only be required if you want to be able to instantly compare more than three files, which we consider to be unlikely.

>>>> Keeping in mind what I wrote above (our goal is seamless switching between files during playback), do you think the variable callback approach would work?
>>> I understand your need here. Question is: How long does it take to load and parse such an HRTF file? Its probably quite fast, and then it should be fine to use a callback. I mean who cares if the switch to the new HRTF file happens only 20 ms after you clicked something in the GUI.
>> As Piotr Majdak wrote in his answer (17th April), the files might even get in the range of GBs.
>> I just did a quick test loading an 80 MB reverberant HRTF file (also contains room information): It takes something like 1.1 seconds to load, which means there would be quite some noticeable delay in the reaction to the user input, even with that files size. And this file only covers source positions (i.e. virtual loudspeaker positions) in the horizontal plane…
> Thanks for the feedback. >1 seconds might be too long indeed.
> But for now, I think the issues I mentioned are not the most important ones, and they are not meant to block your patch from my side. Its probably better to address the other comments first.

Ok, thank you. We are working on an updated version also incorporating the other comments and will probably post a new patch in the next couple of days.

> The only thing I’m still not sure is if the functionality is for such a general audience that it justifies integration into the GUI already as you need to set up / download extra files. (also with respect of other GUIs like for Mac OS)

This is a good point. Maybe integration of the module to the VLC sources without GUI would be simpler and faster and we could still expand it later.
Let's see what the main developers say!?!

On the other hand, you'd still need to download SOFA files even without a GUI. And the GUI of SOFAlizer is actually quite similar to the GUI of Spatializer, which is a standard module integrated in 2.1.
Also note that SOFA applications are currently being developed at many places worldwide (google for "SOFA HRTF") and we thus expect SOFA to become popular soon. This will also help in understanding how SOFAlizer works.

Best regards,

> Best regards,
> David
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