< Back to IRCAM Forum

Output from spat5.hoa.decoder~ / Zoom H3-VR

Spat
#1

Hi,

I am unclear of the positions of the sounds coming from the spat5.hoa.decoder~. I have a 1st order ambisonics file, and the output is 3D with 32 (or just 8) outputs. Where are the sounds virtually located?

Background: I am using a Zoom H3-VR recorder, and need to decode the file so that it is correctly represented in a 32 channel system (8 positions with 4 speakers each on top of each other), or just for starters on an octophonic system. The result is heavy on the right side, so there’s something I’m not getting.

I am aware that the output of the recorder is W/X/Y/Z, but the decoder needs W/Y/Z/X. Playing around with the settings doesn’t help much, but I actually don’t understand where to route the output of the spat5.hoa.decoder~.

Help is greatly appreciated!

Hans

#2

Hello Hans,

The outputs of spat5.hoa.decoder~ are the physical loudspeakers (either 8 or 32 speakers in your case), routed via your audio device.

Some things to check:

  • make sure you properly send the coordinates of the 32 (or 8) speakers to spat5.hoa.decoder~
  • set your Zoom to AmbiX format.
  • set your spat5.hoa.decoder~ to SN3D (which is the normalization used in AmbiX).
  • Be aware the spat uses a X-Y convention different from most other tools; therefore a 90° rotation might be necessary. Have a look at spat5.tuto-bformat.maxpat for further details.
  • make sure you record a simple test file (for instance saying “front”, “left”, “back”, etc.) so that you can easily verify the complete encoding+decoding chain.

Best,
T.

#3

thanks for your answer, and sorry for responding late, but I had to be updated to member status to post.

Yes, I did all that above. Just to make sure, I did a new recording with the Zoom H3 as AmbiX. What I’m currently at is that “left” comes from the left, but “right” comes from the front, both at an angle of 90º. This is on a rectangular/planar 8-channel system, with correct loudspeaker positions. Any ideas what I should look for?

Thanks, Hans

#4

Hum… that is strange.
Could you send (me) your patcher + the recording (just a short excerpt, e.g. with “left” “right” announcement) ? I’d like to check how your decoder is configured.
(you can send private message, in case you dont want to post that publicly)

Best,
T.

#5

I’m traveling currently with not much access to the internet. Thanks for looking into this, I’ll send you the patch + file next week when I’m back!

Hans

#6

Hi T,

I’m back, see patch plus soundfile here https://d.pr/f/Cit6qI. Thanks!

Hans

#7

Hi Hans,

Attached a modified patcher that should guide you in the decoding process.
Admittedly, the left-right test is not totally convincing… Unsure why.

Best,
T.

ambi-decoder-2.maxpat (37.4 KB)

#8

Hi,

I’d like to buy a Zoom H3-VR and this topic is helpful !

What do i have to know before buying ?

Many THX in advance,

Best,

Jerome

#9

great, thanks! I see you’re running it as 3D that automatically downgrades to 2D. I’ll test it out Tuesday.

As for the audio file, I put it through the decoding software that comes with the H3, and while left and right come from the correct directions, the spread isn’t that much.

Thanks, Hans

#10

Hi T.

thanks for the decoder patch. The picture was a little better, but when I modified the patch from 8 to to 32 speakers (now in 3 dimensions) it sounded great. I’ll run more tests soon, may have to record more AmbiX files, most of the older stuff is in FuMa.

Thanks, Hans