Ambisonics: Capture and compatibility

[Russ (Al) Prat]

Steve,

Would you consider starting a new thread specifically regarding ambisonics, how it is captured and treated, how it translates to other delivery formats, and if it can indeed be considered as compatible in relation to stereo/surround formats as M-S was to the mono/stereo compatibility problem. I'm very curious regarding this method but I'm hopelessly behind. Thanks. Of course if it's been covered elsewhere...
RAP

[Westmalle]

That would be very interesting

[Remoteness]

Sure! Let us make it so...

Since you already have started a thread about starting a thread about Ambisonics let's make this the one!

Carry on my fellow Remotesters and guests!

Here's a Wikipedia link about Ambisonics for your review.

[Russ (Al) Prat]

Steve,

There's enough material here (Wikipedia) to keep my mouth shut for a while. Leave it to the British to come up with something like this! I'm sure there will be a lot that's over my head, and I'll post my questions here, please everyone, excuse me if I ask obvious questions, it's easy for me to miss the forest for the trees sometimes. RAP

[mohthom]

Just to dispel a common myth or two about the capture of ambisonic sound;

It doesn't have to be 3D. Pantaphonic (or planar/2D) ambisonics is useful as it can be used to mix down to 5.1 easily.

Sounds recorded with Ambisonic microphones output in so called 'B-format,' but this doesn't mean that sound is 'locked in' forever. Similar to M-S recordings, it needs to be matrixed to get the correct sounds out of it, and when decoded (to however many speakers, but I believe there are pre-made plugins that will decode from B-format to 5.1 etc. - as well as many other off-the shelf and free solutions) can saved as 'G-Format' - essentially a fixed output medium (5.1) that can be played back without special equipment. Ambisonic recordings to 5.1 can be very effective.

Ambisonics DOES NOT REQUIRE SOUNDFIELD MICROPHONES. Soundfield microphones are used commonly because they are;

• Good quality (historically at least)
• The first on the market
• Designed with the collusion of Michael Gerzon (correct me if I'm wrong here, but this is what I picked up!)
• Easy to use - they come with a preamp/decoder in the box.

There are other ambisonic microphones available (!) to buy or build, and a couple are listed below;

• Make your own ambisonic soundfield type microphone
• Core Sound — TetraMic
• Microphone Pages
• nick mariette - sounds orange - diy ambisonic microphone

Good luck!

MohThoM

[Russ (Al) Prat]

Thanks for the info. answering some of my questions before I even had a chance to ask them! Does this format translate well to stereo?

[Russ (Al) Prat]

Er, duh! I read a little farther and answered my own question this time. I'm wondering because it seems like there would be a phasey sound in mono, but I'm going to dig a little deeper and discover a little more.

[mohthom]

From the ambisonics page on Nimbus records . . .

"The finished, Ambisonic recording can be delivered to the user in a number of ways. B-format itself is a very efficient transmission format, conveying full three dimensional sound in only four channels. For single plane recordings, three channel B-format can be used. It is also possible to decode the B-format to a common, regular speaker arrangement for transmission as speaker feeds. The most basic method for transmission of an Ambisonic signal uses a system called UHJ. UHJ is a matrixing system developed to allow Ambisonic material to be transmitted via only two channel media. The two channels are stereo compatible - that is to say you can listen to them as a normal stereo recording on standard equipment - but with a UHJ decoder you can decode them to your chosen multichannel speaker layout."

The emphasis is my own. The source text is from DVD Music Introduction

You may also want to check out Visual Virtual Microphone

MohThoM

[Westmalle]

nice links I found:

Ambisonic Studio
Procédés et systèmes d'enregistrement et de reproduction du son en 3D
Procédés et systèmes d'enregistrement et de reproduction du son en 3D / Chapitre 2
Procédés et systèmes d'enregistrement et de reproduction du son en 3D / Chapitre 2
Procédés et systèmes d'enregistrement et de reproduction du son en 3D / Chapitre 3
Procédés et systèmes d'enregistrement et de reproduction du son en 3D / Chapitre 4
Procédés et systèmes d'enregistrement et de reproduction du son en 3D / Chapitre 5
Procédés et systèmes d'enregistrement et de reproduction du son en 3D / Chapitre 6

Ambisonic Studio | B-Format to Stereo UHJ with Nuendo
Ambisonic Studio | Stereo UHJ to B-Format with Nuendo
Ambisonic Studio | Hybrid Surround Sound Mixing with Nuendo
Ambisonic Studio | Native B-Format Recording
Ambisonic Studio | Decoding B-Format Music to 5.1 Surround
Ambisonic Studio | Comparative Surround Recording
Ambisonic Studio | Fifth Order Planar B-Format Encoding and Decoding
Ambisonic Studio | Zoom2Five Plug-In
Ambisonic Studio | DMS2Five Plug-In
Ambisonic Studio | B2X Plug-In Suite

[boojum]

I have not lived in Montreal for 30 years now. My French is very rusty. Are there English translations for the UofM papers anywhere? Bilingual by law???

[Westmalle]

Originally Posted by boojum

I have not lived in Montreal for 30 years now. My French is very rusty. Are there English translations for the UofM papers anywhere? Bilingual by law???

sonic surrounds » Blog Archive » Proliferating Ambisonic Microphones

Ambisonic Studio | Fifth Order Planar B-Format Encoding and Decoding

http://www.radio.uqam.ca/ambisonic/images/eigenmike.jpg

http://www.radio.uqam.ca/ambisonic/i...lmic_small.jpg
http://www.mhacoustics.com/page/page/2949006.htm

[Russ (Al) Prat]

Although I have a lot to study, (and there's a lot out there to study) I have always been impressed by the almost magical realism in an M-S recording. From what I have read so far, the same principles apply to ambisonics. A 5.1 recording on a typical consumer home theater setup sounds cheesy and cheap, gimmicky as it were. Has anyone done comparisons on an average low end system with ambisonic recordings? How does it fare? In my limited experience 5.1 only sounds convincing in the sweet spot of a symmetrical ambience. Yet I read that ambisonic playback functions even outside of the sweet spot. If this is so, then obviously ambisonic technology is far superior to 5.1, yet requiring less channels.

Major record labels still control distribution, but a concerted effort could get the attention of speaker manufacturers, who in turn could offer ambisonic speaker packages and perhaps increase consumer awareness regarding ambisonic technology. It is a shame seeing superior technology once more losing to superior marketing. Perhaps someone who thoroughly understands could explain it in layman's terms, explaining the shortcomings of 5.1 and how ambisonics avoids those shortcomings and delivers a superior reproduction.

In a multitrack recording situation, I can see how it could be used for key instruments, vocals, drums and percussion, piano(wow!) and nearly everything. But in multitracking, isn't there bound to be a saturation point where room acoustics begin to get crowded and phase starts to be a problem? Would one make an array along the lines of a Decca tree? It seems like to be effective one would need quite a large studio. RAP

[mohthom]

I don't know if I follow you . . .

In a multitrack recording situation, I can see how it could be used for key instruments, vocals, drums and percussion, piano(wow!) and nearly everything. But in multitracking, isn't there bound to be a saturation point where room acoustics begin to get crowded and phase starts to be a problem? Would one make an array along the lines of a Decca tree? It seems like to be effective one would need quite a large studio. RAP

Amisonic microphones are single units with four capsules in. No array is needed - it's all in a single microphone housing. If you do it yourself (using planar techniques - blumlein plus omni) then you can set it out like a blumlein . . . plus an omni! It's not a huge array. It should be set as tightly as possible to minimise phase problems. Soundfield microphones are popular becuase the capsules are so close together that they solve many of these problems for you. There is a huge something to be said for LDCs in ambisonic arrays (mmmmmm . . . . my favourite!), and it would be possible to spot individual instruments at encode the signal to appear at particular points in the soundfield (a little like panning the signal, but around a circle, including distance) - but I don't know how successful this would be as it's something I've not done.

More than any other array the room needs to be great for ambisonic recordings.

MohThoM

[matyas]

This has made for some fascinating reading, and I haven't even made it through a quarter of it!

[mohthom]

I just noticed the tags at the bottom - does someone mean audio file or audiophile?

MohThoM

[Kewl]

Originally Posted by Westmalle

nice links I found

Hi there, I'm Daniel Courville, the one responsible for the those links.

The French master thesis will likely never be translated since there's already a wealth of info on Ambisonics in English: of course the Wikipedia entry comes to mind, but also a few other references that are linked in my English website, Ambisonic Studio. I will add that if you want to experiment with Ambisonics, but don't have access to hardware for producing some, Ambisonia is a repository of acoustic and synthetic B-Format files. Those files are downloaded via BitTorrent.

- Daniel

[Westmalle]

Originally Posted by Kewl

Hi there, I'm Daniel Courville, the one responsible for the those links.

The French master thesis will likely never be translated since there's already a wealth of info on Ambisonics in English: of course the Wikipedia entry comes to mind, but also a few other references that are linked in my English website, Ambisonic Studio. I will add that if you want to experiment with Ambisonics, but don't have access to hardware for producing some, Ambisonia is a repository of acoustic and synthetic B-Format files. Those files are downloaded via BitTorrent.

- Daniel

Hi Daniel!
Glad to see you here!
May I ask you some questions?

Is it physically possible to make a Soundfield microphone with 3 or 4 big ribbons such as AEA?

[Kewl]

Originally Posted by Westmalle

Is it physically possible to make a Soundfield microphone with 3 or 4 big ribbons such as AEA?

It's certainly worth trying in a "Native B-Format" assembly (two fig-8s and one omni, also known as "Nimbus-Halliday"). I would test it with ribbon microphones that have uniform frequency response and directivity on both sides.

- Daniel

[Russ (Al) Prat]

Daniel,

Congratulations on the site, etc. It looks like you've been involved for a while in ambisonic production so I get the impression that there must be some sort of market out there. Are there any particular market segments, or budding niche markets that you've found responsive? Forgive the mercenary approach, but I need to convince an investor that it is a worthy cause! RAP

[Russ (Al) Prat]

Originally Posted by mohthom

I don't know if I follow you . . .

Amisonic microphones are single units with four capsules in. No array is needed - it's all in a single microphone housing. If you do it yourself (using planar techniques - blumlein plus omni) then you can set it out like a blumlein . . . plus an omni! It's not a huge array. It should be set as tightly as possible to minimise phase problems. Soundfield microphones are popular becuase the capsules are so close together that they solve many of these problems for you. There is a huge something to be said for LDCs in ambisonic arrays (mmmmmm . . . . my favourite!), and it would be possible to spot individual instruments at encode the signal to appear at particular points in the soundfield (a little like panning the signal, but around a circle, including distance) - but I don't know how successful this would be as it's something I've not done.

More than any other array the room needs to be great for ambisonic recordings.

MohThoM

Don't worry about following my posts, I hardly even make sense to myself, yet alone to others! Ha! The day before yesterday I was getting rid of some trash that a friend left behind when he moved back to the States. As I emptied one sack a CD fell out, a ripped version of Time Out by the Dave Brubeck Quartet. It appeared to be ruined but I put it on the computer and got all the tracks... what a treat! This is the vision I have for Ambisonic recording, good musicians in a good room with good mics and pres. Here in Rio they have a native jazz called chorinho that would be perfect for Ambisonic recording, all acoustic, sort of an urban bluegrass and lots of fun. Anyway, thanks for the tips! I'm very interested in geting this rolling, I just need to convince "Meester Beeg" that it's worth the investment. Have a good Sunday! RAP

[Kewl]

Originally Posted by Russ (Al) Prat

It looks like you've been involved for a while in ambisonic production so I get the impression that there must be some sort of market out there. Are there any particular market segments, or budding niche markets that you've found responsive?

I've been interested in Ambisonics since 1990, but actually involved in production, I would say only since late 2006...

Ambisonics is around since the late seventies and although there are numerous hypotheses why it never got off the ground, my personal conviction is that it's mainly due to the lack of available tools. The SoundField mic was always an expensive proposition and hardware analog processing was never widely available.

That's why my no. 1 priority when I started Ambisonic Studio was to shed some light on Ambisonic production workflow and make some processing tools.

As for the market, even if the plan 30 years ago was for the direct distribution of B-Format to the customers, this now seems very unlikely. We're left with Ambisonics as a surround and stereo production philosophy, one that can be discretly implemented without the whole world knowing about it.

The investment is not that huge: some flavour of Ambisonic microphone (SoundField, TetraMic, native B-Format), some software processing, a DAW and a computer platform that can support all this. If the audio interface and monitoring is already multichannel, you're in business.

The key is to have control on most of the production process, so likely markets are music related. Also, the exhibition/interactive installation is a good market.

Last fall, I gave an Ambisonic workshop and two of the participants were from the film industry and they surely gave the impression that it would be hard to implement in that industry because the audio production is quite segmented and involves too many people.

- Daniel

[Russ (Al) Prat]

Daniel,

Thanks for the info and your view on the market possibilities. What are your plans for the future in relation to ambisonic production? What really caught my attention when I first started reading was the inclusion of height in the listening environment and the fact that it was closely related to Blumlein's work.

[Kewl]

Forgot to mention, but the game industry is also a good candidate for using Ambisonics. There's already a PS3 game using it.

Originally Posted by Russ (Al) Prat

What are your plans for the future in relation to ambisonic production? What really caught my attention when I first started reading was the inclusion of height in the listening environment and the fact that it was closely related to Blumlein's work.

When you actually read the whole Blumlein classic patent it becomes evident that the guy was really ahead of his time...

The inclusion of height in surround sound greatly improves the naturalness of reproduced sound, but probably won't be making its way into mainstream audio production. The exhibition and interactive environment seem the most likely candidates to use it.

As for me, since my background is more "academia" than production, I'll continue developing software solutions for Ambisonic production. I wouldn't mind having more classical music productions, but I'm not really in that circle...

- Daniel

[mohthom]

Daniel,

What's your opinion on the writings of Dave Malham?

MohThoM

[Kewl]

Originally Posted by mohthom

What's your opinion on the writings of Dave Malham?

I see Dave and myself in roughly the same zone: he's longtime lecturer at York and he's always been involved with the actual production process of Ambisonic: developping hardware/software solutions, setting up studios and concert halls for electroacoustic playback.

So I would say he's very well informed, experienced and actually interested in using Ambisonics, not just analysing it. Some of his webpages are the basis on which some, if not most, of my plug-ins are built.

- Daniel

[mohthom]

Daniel,

I guess I was really asking about the four hundred thousand speakers thing . . . I'm sorry, that's my fault - I should have just asked!

MohThoM

[Kewl]

Originally Posted by mohthom

I guess I was really asking about the four hundred thousand speakers thing . . .

I think you're referring to this: "if you truly wished to reproduce the soundfield present in a two metre sphere up to say 20 kHz then from information theory it is possible to show that you would need several hundred thousand channels and loudspeakers".

The number and the image of it can certainly lead to disbelief, but it is exact. If you want a sound to come from a precise azimuth, elevation and distance, and want this position to be accurate over the largest listening area, there's nothing like actually putting a speaker at that position and make the sound come out only from that speaker. Now multiply that by all other possible positions.

The statement and the rest of the argument (not quoted here) is there to make a point: the more the speakers, the better, but you also have to be practical about it.

- Daniel

[mohthom]

I'm not so sure . . . he argues it in 'real life' as well . . . .

MohThoM