H3-VR Recording Formats Question

Discuss the Zoom H6, H5, H4, H4n, H2, H2n, and H1. Please don't "post and run". Participate in the discussion. Thanks.
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Desdinova
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H3-VR Recording Formats Question

Post by Desdinova » Mon Nov 12, 2018 10:37 pm

Hello! I just got the H3-VR and I'm a little confused as to the differences between some of the format options. I'm clear on Stereo and Binaural but the other options I'm a little uncertain of. I tried googling around but couldn't find a clear (read: dumbed-down) description of the differences between FuMa, AmbiX, and Ambisonics A.

As I THINK I understand it, all three basically record in identical formats with a different channel assignment in FuMa and AmbiX while Ambisonics A just records the whole 360 soundfield in a "raw" format without specific channel directing. Is this correct? If not, what are the differences/advantages of these three formats? I have no use for 360 VR or video use, I'll be dumping all recordings down to 5.1.

Thanks!
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fotoralf
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Re: H3-VR Recording Formats Question

Post by fotoralf » Tue Nov 13, 2018 4:56 pm

Ambisonic A-format simply records each microphone on one of the four tracks. It is a little like the RAW image from a DSLR. It needs to be developed before its fit for human consumption.

Ambix and Fuma are so-called B-Formats. They're also not yet suitable for direct listening. Imagine them as some kind of multi-dimensional MS-format. With MS stereo you have two signals: mid and side.

Here, the 'mid' signal is called W and the 'side' signals are labelled X, Y, and Z for left-right, front-back, and up-down.

The only difference between Ambix and Fumo is the channel order with Ambix being the more current of the two.

Even if you only want 5.1 I'd still recommend recording in B-format and then convert to whatever you want or need (even at a later date) using the supplied computer software. This way, you don't lose any information and keep all options open for any future use of your recordings.

Ralf
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Desdinova
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Re: H3-VR Recording Formats Question

Post by Desdinova » Tue Nov 13, 2018 11:13 pm

Thanks for the reply!

But I'm still a little confused: if A format is recording "raw"and all three formats are using the same set-up, mic-wise, what advantage do the B formats have over A? Wouldn't all three create identical soundfields when mixed to 5.1 with the Zoom software?
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Re: H3-VR Recording Formats Question

Post by Wulfraed » Wed Nov 14, 2018 11:48 am

From the description, the A format has no internal matrixing; it's just four mono tracks from (cardioid I presume) elements aimed in some configuration. Equivalent to plain X/Y stereo.

The B format is main sound, and three difference tracks, said tracks oriented in left/right, front/back, and up/down. Main+left/right is basically an M/S signal. It is a 3D sound field (5.1 surround is still a 2D sound field -- a flat plane, no up/down). {Following is hypothetical, based upon the description} For playback, visualize sitting in the middle of a cube with a speaker in the center of each wall/ceiling/floor. To produce the sound for the left speaker, the matrixing adds main+left/right, while the right speaker is main-left/right. Do the same with main&front/back, main&up/down.

Converting to 5.1, at simplest, will remove the up/down signal (since 5.1 doesn't have height, just azimuth placement), and then map things to FR/FL, RR/RL, main (that means mixing left&front, left&rear, right&... to create the 5.1 surround/satellite signals).

I would suspect that the B formats are directly usable by sound systems in things like 3D VR amusement rides/simulators.
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fotoralf
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Re: H3-VR Recording Formats Question

Post by fotoralf » Wed Nov 14, 2018 1:55 pm

Wulfraed wrote:
Wed Nov 14, 2018 11:48 am
I would suspect that the B formats are directly usable by sound systems in things like 3D VR amusement rides/simulators.
You can include B-format audio in videos for upload to Youtube with 360 degrees images and the sound stage will follow the image if you rotate it.

Another difference between A and B is that ambisonic microphones can be calibrated and those calibration data can be used in converting from A to B so you end up with a B format that is cleaned of the phase and frequency response flaws of the microphones used to create the original A format. I can't say if Zoom use this possibility or not. The software has a switch labelled "Ambisonic Correction Filter". The description of this function is rather vague but maybe this is it, although this should be used before the conversion to B format. Then again, Zoom are also known for limiters applied after the A/D conversion, so who knows.

Ralf
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surround audio and panoramic photography in western europe
audio examples: http://aporee.org/maps/projects/fotoralf
blog (German): http://the-real-fotoralf.blogspot.com/

Desdinova
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Re: H3-VR Recording Formats Question

Post by Desdinova » Wed Nov 14, 2018 10:45 pm

Okay, I think I have my brain wrapped around (pun intended!) all of this.

A-format records straight four channel, with guidance data (matrixing) relating to up-down basically omitted. B-format records four channels WITH guidance data on three of the tracks. And if I STILL got it wrong, it's no huge deal; it seems like the best solution to just record in B-format so as to have more conversion options down the road.
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Re: H3-VR Recording Formats Question

Post by fotoralf » Thu Nov 15, 2018 6:08 am

Desdinova wrote:
Wed Nov 14, 2018 10:45 pm
A-format records straight four channel, with guidance data (matrixing) relating to up-down basically omitted.
Well... kind of... :-)
...it seems like the best solution to just record in B-format so as to have more conversion options down the road.
Exactly.

Ralf
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surround audio and panoramic photography in western europe
audio examples: http://aporee.org/maps/projects/fotoralf
blog (German): http://the-real-fotoralf.blogspot.com/

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Re: H3-VR Recording Formats Question

Post by Wulfraed » Thu Nov 15, 2018 7:59 pm

Desdinova wrote:
Wed Nov 14, 2018 10:45 pm
A-format records straight four channel, with guidance data (matrixing) relating to up-down basically omitted.
Just downloaded the manual, and based upon the illustration, and given the tetrahedral microphone placement, I would have to say the the four channels in RAW mode are:
front-left-up, front-right-down, rear-right-up, rear-left-down (Heh... I derived that from the cover image, but page 8 of the manual uses just that description -- change my "rear" to manual "back")

That is: EACH channel contains data pertaining to all three axes.

The B format gives you a general (centered) sound field (W), and three delta files which can be matrixed for X/Y/Z orientation.

The conversion software can work with either, and produce 5.1 planar surround -- the software allows one to first define the "plane" before generating output files.
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Baron Wulfraed
IISS Elusive Unicorn (detached)

Superscope PSD-300; BOSS BR-600, Zoom HD16cd, Zoom R16, BOSS BR-800, Zoom H2n
Now to (re)learn to play an instrument

Lanikai S-C, SMC-E; GoldTone Banjo-Uke; Flatiron 1C, A5; Big Muddy M1-W; Ovation MM68AX, CSE-44; Orpheus Valley Fiesta FS; Taylor NS-72ce, T5-S1; Musima (4st, 20 fret, tenor-tuned) banjo; bongos, dumbeks, bodhrans, hand drum, tambourine; recorder: soprano, alto, tenor; Cedar Flute (5 sizes); Pennywhistle (3 keys); Casio keyboards

Desdinova
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Re: H3-VR Recording Formats Question

Post by Desdinova » Thu Nov 15, 2018 10:15 pm

Okay, now I have a good understanding about all of this. Thanks so much for the patience and clarifications!!
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