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Mar 23, 2008 9:04 AM in response to Marc Verhoevenby John Buehler,B-format needs to be decoded, and there is no provision for this in SD. I would contact the person who is hosting those files to find out how they are using the impulses, but I don't think SD will be able to do it. -
Mar 25, 2008 4:49 AM in response to John Buehlerby Marc Verhoeven,Hi John, thanks for answering, but I think there is:
From the manual: New Features in Logic Pro 8, page 30:
"Space Designer now supports any impulse response format up to 7.1 (including
B-format)." (there are also mentions in Impulse Response Utility-Manual(you can make them and Logic Studio Instruments and Effects, latter says:" Impulse Response Formats
Any mono, stereo, AIFF, SDII, or WAV file can be used. In addition, since Space Designer
supports surround formats up to 7.1 surround, discreet audio files and B-format audio
files that comprise a single surround IR can also be used. "
And from Space Designer: If you go to the preset menu, and from there to :
-04 Surround Spaces/01 Surround Rooms/ 0.4s Drum Booth Three
You get "Omni B-format"
I did "Show in Finder from the IR-popup, if you open the 00.4s Drum Booth Three-OBF.SDIR with something like the trial of Snapper (audioease.com) I see a 4ch AIFC file, not really encoded I think, just every channel has another function with B-format, as I understood it.
But if I make a 4channel file of the WX+YZ files it doesn't get recognized as B-format. So my guess is, it's just something that has to be set in the header of the soundfile.
Question, how? with what utility?
thanks, marc -
Mar 25, 2008 6:55 PM in response to Marc Verhoevenby John Buehler,Yeah man, I see. This is clearly an under-documented aspect of SD. Everything I know about b-format says that you need a decoder for playback, meaning the end user. So while it is suggested that it will handle b-format, it says nothing about actually decoding it. There definitely aren't any tweaks for decoding in SD, and it seems like b-format decoders have plenty of tweaks. The ambisonics format that does not require decoding is g-format. So, I have no idea. It does seem that there is a mode to be set, but I can't figure out how to set it. Maybe it's in the header, but I kinda doubt it. That would mean it was it's own kind of audio file, which it's not. It's just a 4 channel setting. I'm curious to know how this all shapes up for you, let me know how it turns out, if you ever figure it out. -
Mar 28, 2008 1:22 AM in response to John Buehlerby Marc Verhoeven,Hi John, for a moment I thought I found it (finally; after googling for hours, visiting loads of interesting sites about ambisoncs etc, no lost time
Anyway, Compressor does it; or should do it. Inside Compressor the QuicktimeAiff encoder has loads of extra surround options; 1 of them is " Ambisonic B Format (W X Y Z)"
Unfortunally, when I fed it a 4ch file, the output was a 2ch file, no sign of Ambisonics.
But I'm not so familiar with Compressor, maybe it's a bug, maybe I did soemthing wrong, I'll find out. -
Mar 28, 2008 4:26 AM in response to Marc Verhoevenby DaCaptain,It requires a bit hacking, but it works.
1: Download the files you found in the net and convert them to AIFF using Quicktime.
2. Start IRU, tell it to create a stereo project and drag the file with the WX channes into the editor. IRU imports the file and displays the channels.
3. Save this project as "A".
4. Drag the file with the YZ channels into the editor and save it as "B".
Now you have 2 SDIR projects on your system.
5. Create a new project "mono to B-format". Set Sweep to "off" and record some bogus material to the 3 tracks. Save it as "C" and close IRU.
6. Now comes the hacking: The IRU projects are just packages, open them with the Finder using the context menu option "Show package Contents". You see some files like 1.aif and 2.aif, a Session.plist and a Sweep.aif.
7. Now you replace 1.aif and 2.aif of the C.SDIRproj by 1.aif and 2.aif of A.SDIRproj.
8. Rename 1.aif of B.SDIRproj to 3.aif and replace 3.aif of C.SDIRproj with this one.
9. Open C.SDIRproj with IRU et voila, the WXY tracks contain the desired audio.
10. Now create the SpaceDesigner IR pressing the lower left button.
Hope this helps!
Da Captain -
Mar 28, 2008 2:31 PM in response to DaCaptainby Electronathan,I tried this and I think it's working for me.
In my SD is the preset I made from the IRU and it seems to registar as Omni B-format.
A question: Wouldn't you want to use True Stereo vs B-format? Or how about; please just a quick explanation about the latter?
thanks
PS: the IRs from the site in question sound excellent! -
Mar 31, 2008 6:11 AM in response to Electronathanby Marc Verhoeven,Nice hack!
I think you can improve it a bit, I did:
1) Convert the files to split channel .aif & rename to 1.aif, 2.aif, 3.aif, 4.aif
2) Copy a SDIR from your /Library/Audio/Impulse Responses/Apple/04 Surround Spaces to the directory were your 1.aif etc. are.
(I used /Library/Audio/Impulse Responses/Apple/04 Surround Spaces/01 Rooms/02.0s Villa Lobby-OBF.SDIR )
3) Open the "02.0s Villa Lobby-OBF.SDIR" with IRU. (do info in the Finder, set Open With.. to IRU, + change all, later you can then doubleclick any SDIR).
4) Save Project As... Close Project
5) replace the 1,2,3,4,aifs from the package with your own
6) Open the project again with IRU, Create SpaceDesigner setting.
In this way you don't lose the Z-channel of the B-format. The IRU manual says (I think) that's it's not used, but it might be in the future.
BTW found a bug, sometimes 1 channel is lost when opening a 4channel SDIR with IRU. You'll notice when you click Audition IR...
And you have to adjust your systems samplerate.
Some more information about B-format is inside the IRU manual. +
http://en.wikipedia.org/wiki/Ambisonics
http://www.radio.uqam.ca/ambisonic/b2x.html
http://www.ambisonia.com/ -
Mar 31, 2008 6:19 AM in response to Marc Verhoevenby Electronathan,I'm finding this thread to be surprisingly useful!
I wasn't expecting to get into the IRU app and surround IR formats, but heck, it's here and I'm diggin' it.
I'm gonna read through those links you posted and if I still have questions I'm gonna hit this thread up again...
peace -
Mar 31, 2008 6:55 AM in response to Electronathanby Electronathan,OK, so I do have a basic question which I'll relate to Space Designer and Logic.
Is there no point to using b-format SDIRs when running SD stereo? Last week when I tried a b-format setting in SD, but panned the incoming signal hard left/right, the same result would happen that SD would not produce signal from the IR's W (omni-directional, mono, no?) source when its input is set to full stereo.
So there are two questions really: same difference using b-format in a stereo mix? Was I wrong to assume that the extra dimensions in the SDIR file would create a constant IR for hard panning of the dry incoming signal?
Thanks -
Apr 3, 2008 2:01 AM in response to Electronathanby Marc Verhoeven,hi Electronathan,
-might have been better starting another topic about this, or hijack this one: http://discussions.apple.com/thread.jspa?threadID=1460002&tstart=0
Anyway, if you put SD on a mono or stereo Audio or Software Instrument Track, and if you hard left or right, you pan everything on the channelstrip with it. The Pan is Post-FX.
So you have use an Aux channel.
From then on it depends on the IR what the direction outcome is, when panning the Source-channel.
But there's no point (I think, correct me if you see a point) in using a B-format IR on a stereo-aux.
It's mono to WXY, so the panner of the sourcesignal becomes useless
If you want a true-stereo reverb you'll have to use true-stereo IR. Logic comes with just a few, the presets of those are ending in "+"; the SDIR's are having CTS in there name, and you see "Discrete Circel" in the SpaceDesigner Gui.
Hope this helps, I'm also pretty new to this deeper IR-stuff, so hope it's correct. -
Apr 3, 2008 2:10 AM in response to Marc Verhoevenby Marc Verhoeven,Another link for B-format and surround IR's:
http://www.acoustics.hut.fi/projects/poririrs/