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Andrew Price wrote:
<blockquote
cite="mid:BANLkTi=_KSbEyrpdz=A4nCx5H0opb++Y1Q@mail.gmail.com"
type="cite">Hi everyone,
<div><br>
This is something I would be interested in seeing in VLC. HRTFs are
nice and in many cases produce better surround sound than actual
surround sound speakers.</div>
</blockquote>
<br>
Thanks for the nice "welcome".<br>
<br>
<blockquote
cite="mid:BANLkTi=_KSbEyrpdz=A4nCx5H0opb++Y1Q@mail.gmail.com"
type="cite">
<div>I can't think of any open source implementations since most
implementations are commercial such as Dolby Headphones and the
hardware accelerated Creative CMS-3D.</div>
</blockquote>
<br>
>From the signal-processing point of view, the implementation is quite
straight forward. The actual issues will appear if the software
framework limits the filtering. These issues (among others) should be
addressed during the project. <br>
<br>
>From the psychoacoustic point of view, individualized HRTFs should be
used and I plan to provide an option to load listeners-specific HRTFs
to VLC. In case where individual HRTFs are not available (valid for the
most of the listeners outside our lab ;-) we will provide a database.
In the first version, the users will have a choice of an HRTF set which
he will like. Later, maybe we'll implement some of the recently
published methods to customize generalized HRTFs. On a long term, we
are working on alternative methods to obtain individualized HRTFs. But
here we are talking about 3 to 5 years ;-)<br>
<br>
<blockquote
cite="mid:BANLkTi=_KSbEyrpdz=A4nCx5H0opb++Y1Q@mail.gmail.com"
type="cite">
<div>I once found a 'virtual sound card' for Windows that act as a
5.1 or 7.1 soundcard then outputs a stereo stream which you can play
directly to your headphones (I don't remember the name of the software
but it was by an Australian company). The downside of this is the CPU
usage as the driver is always running and mixing and it might introduce
notable latency to the audio. But the surround sound effect was really
good, as long as you spent some time configuring each individual
'virtual speaker' to your headset/ears (you could tell each speaker to
move lower/higher, forward, back, closer, etc).</div>
<div><br>
</div>
<div>There is also Rapture3D (<a moz-do-not-send="true"
href="http://www.blueripplesound.com/index.php?target=products&phpsessid=b45965f0f5dd4d1a1474fb478c44777c">http://www.blueripplesound.com/</a>) which
is a drop in OpenAL placement for Windows. I don't know if anything
exists for Linux.</div>
</blockquote>
<br>
At the moment, we have a <a
href="http://www.kfs.oeaw.ac.at/content/view/608/606/lang,8859-1/">database
of HRTFs</a> and simple convolving the signal with a pair of HRTFs will
produce spatialized sound. Some additional tricks are required to
increase the naturalness and externalization - we are working on that
at the moment and the results could be incorporated into VLC.<br>
<br>
<blockquote
cite="mid:BANLkTi=_KSbEyrpdz=A4nCx5H0opb++Y1Q@mail.gmail.com"
type="cite">
<div>It would be great to have HRTF built in to VLC for multiple
reasons. Since VLC is open source it would be a great reference code
for future HRTF work. HRTF could be used to compress audio during
streaming (by streaming stereo audio rather than a lot of independent
audio channels). Most importantly, HRTF would be available to everyone,
not just those that have specialised drivers.</div>
</blockquote>
<br>
I'm afraid that our intended implementation will be a simple
convolution of the audio signals with the appropriate HRTF for a given
sound direction. We also could have a simple room model to include a
more natural reverberation (I think there is something like that
already in VLC). I have no idea if our approach will be able to reduce
redundancy in the streaming - sorry.<br>
<br>
regards,<br>
Piotr<br>
<br>
<div class="moz-signature">-- <br>
Piotr Majdak<br>
Psychoakustik und Experimentelle Audiologie<br>
<a href="http://www.kfs.oeaw.ac.at">Institut für Schallforschung</a><br>
<a href="http://www.oeaw.ac.at/">Österreichische Akademie der
Wissenschaften</a><br>
Wohllebengasse 12-14, 1040 Wien<br>
Tel.: +43 1 51581-2511<br>
Fax: +43 1 51581-2530</div>
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