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Wireless VOIP?
zambuka asks: "Recently I was asked about pricing and availability of wireless microphones. What is needed are 15 wireless microphones, appropriate base units and the ability to record the signal from each microphone on a separate track. A session will last about 2 hours and the results need to be recorded to a CD. I have priced this at about $25000AUS probably less with bulk rates for the mikes and transmitters but still a big cost and not particularly portable for the base and recording units. The question I have regards alternatives. I have thought about using MiniDisc recorders, Nomad and Muvo. These are a much cheaper alternative and will suffice but require a major effort to transfer everything back to a PC and burn to a CD. I was also looking at wireless networks: 802.11a/b and Bluetooth and thought about how much cheaper and more suited to my needs this technology seems to be. Can these wireless systems cope with the constant throughput I need for this? And, is it possible (preferably with off the shelf components) to set up a wireless VOIP or similar network capable of dealing with this quantity of audio and recording the signals separately. Links to the tech would be welcome. Anyone living in Canberra who would like to take a shot at setting something like this up can feel free to contact me."
i'm sure this sort of thing is possible... but will VOIP give you the sound quality that you're looking for? and with that many microphones... will you have the wireless bandwidth?
Somewhere on this page I have hidden my signature.
There are some folks in Fort Meade and Langley with experience in this area who might be able to offer a few pointers.
Anyone living in Canberra who would like to take a shot at setting something like this up can feel free to contact me."
Translation: Anyone who wants to do lots of unpaid work for me is free to do so.
May we never see th
I can see several problems with using 802.11b as a basis for a wireless microphone system, sufficient problems that I'd have to recommend you not attempt it, unless you really feel like tinkering.
First off, bandwidth may indeed be a problem, especially if you want high-fidelity results. A single mike recording at CD quality would require approximately 88K/s or 700 kilobits per second. 15 channels would over 10 megabits, assuming perfect efficiency -- which you wouldn't get with 802.11b without some fancy custom programming, so you'd need a set-up with at least 20 megabits of bandwidth. If you need to use these audio sources for professional mixing, the bitrate would double, to 40 megabits.
I'm aware of no commercial solution for a high-fidelity, low-power A/D converter for wireless microphone use. The ones I know about eat quite a bit of electricity and wouldn't be suitable for battery-powered applications. Building them would be difficult if you wanted to preserve fidelity.
You would further need to provide a small computer with each microphone and A/D converter, in order to feed that data onto the wireless channel. The task of coding for a single-chip processor or a small experimenter board would be difficult enough, but to keep electronic noise out of your audio circuit would be non-trivial. Powering it by battery would also cause problems.
- 15 wireless microphones
- Base units
- Record each signal on it's own 'track'
- Up to two hour recording period
- Record results to CD
From your further discussion, I'm assuming the following:- Small microphone transmitters, user wearable, light
- Mobile users
- Small working area (wireless mics, 802.11 don't go very far)
- Medium or lower sound quality (good for voice, but not much else or you wouldn't suggest voip)
And this is enough information to suggest exactly what you suggested. If you told us better parameters, such as distance, typical usage (theatre, I'm assuming), obstacles between wireless microphones and recording system, etc.I wouldn't suggest you do anything with voip right now unless you want to roll your own. It's more expensive, and at this point less mature and dependable than a basic wireless mic system. Unless you like babysitting the recording system...
So go with regular wireless mics. Be aware of contention and crosstalk. You can get wireless mic receivers that will support more than one mic simultaneously, and they are typically rack mountable. Put four 4 channel receivers in a small rack mount box with a rack mount computer. Now look for a multichannel recording card. You could go with 8 individual sound cards, but finding a mobo to support them would be a fun trick) The multichannel card should come with basic multitrack software. Perhaps a programs such as audacity will work with them. Beyond that you should be able to recording the resulting wav files to CD.
I wouldn't bother with having a bunch of little minidiscs of other individual recorders. To many little points of failure.
You might be interested in a few other options. You can get full duplex radios such as those used in cordless telephones from laipac.com. I'm currently using a cordless telephone for bike rides and other short distance communications. Last winter I mulled the idea over in my head of making a voip phone with 16 bit 802.11b cards (compactflash or pcmcia). It would take a relatively low power microcontroller to encode the communications. Since 802.11b doesn't have any real-time capabilites or QOS service, you won't get even packet rates. But since you didn't mention that the sound was going to listened to as it was created, and the computer can buffer just fine, you only need to time stamp each packet and the computer can still do a full recording with only a little buffer at the transmission side.
-Adam
Bull<cough>shit.
Like QoS matters. Until you have congestion. And when you have congestion in this application you're screwed anyway, regardless of what QoS you have.
Was this some sort of troll or just cluelessness?
<sigh>
Poof.
Heck this is just basic multitrack recording (even down to making a CD out of it). Have you tried hitting the local music store? Is this what you looked at already? Seems like it will be fairly portable to me...
Get a bunch of wireless lavalier microphones (the small ones the clip on someplace). For instance, Shure is one company I know of. I believe a 100+ channel receiver is under $2000 and each mic+transmitter will be around $500.. Let's say you get a bulk discount so that's another $5k.
Then you need a mixer, let's get a good one for $1K.
Then you need a powerbook with a burner and sound input, let's say $3k for that.
Finally you need a copy of Pro Tools multitrack recording software. You *probably* could get by with Pro Tools Free, which is $zero, or buy a full version (I can't recall exactly what's available right now but let's just totally make up a number: $2000).
If you actually need to record each track separately, then you'll pay a bit more for some kind of external box. Again let's make up $2000 for that.
So it looks to me like you can put this together for under $15,000 easily...what did I miss ???????
what audio quality is needed and how real time does this need to be?
one decent solution would be to use 15 DV cameras pointed at synchronized clocks (or the same clock if they're close enough). then you can figure out the audio offsets from the video signal, toss the audio and mix+burn the saved synced audio.
First of all, why assume you need to -buy- 12 wireless mics when your application may only require that you -rent- them. Next, forget about 802.11 and VOIP. This is a job for a competent sound man. Your wireless mics should have "diversity reception." This means there are two receiving antennae per mic, this will eliminate annoying, noisy dropouts caused by radio frequency wave reflection -- if the signal drops out at one antenna the circuitry will flawlessly switch to the audio from the other antenna. Manufacturers of wireless diversity mics include Nady Systems and Cetec Vega. You might be able to find some of their products on eBay. As far as recording, you need to buy or rent, yes, a 12-track recorder. Find someone who knows the field of wireless, such as a ham radio operator. Consult a pro audio store in your nearest large city. Don't forget to use fresh batteries in your wireless mics.
A standard wireless mike from places like DSE (Dick Smith Electronics, equiv to maybe Radio Shack in US) have the problem of drift and that they use the commecial FM band. a) you don't have much room for your signals, especially if you are in a built up area, and b) the signals drift due to not using PLLs.
If you look on the net, you should find some PLL wireless mikes. You won't be able to make them very small, I would estimate you should be able to make them (the transmitters) the size of say a small paperback book.
The receivers are part of the same design, as for recording the audio tracks, that can be done by many different means. If you want post editing possibilities, you'll need either a professional recording device, that can record many tracks onto one media. Or you'll need 15 different recording devices (8 if you only record mono and use a stereo recording device). As for what you use, I can't recommend much more on that, other than try google.
Now, back to the transmitter/receiver. Most commerical units, atleast in NZ (and I believe in AU), use the TV band VHF band, just below standard FM radio. Newer units use the GHz bands, but they are harder to build (less tolerances at higher bands).
However, come to think of it, you can pick up some video/audio GHz transmitters/receivers pretty cheap (I'm not talking about using off-the-shelf, they are still expensive afaik). I'm sure you'll be able to find a company that sells GHz audio transmitters for a cheap price.
You mentioned run time. 2 hours should be reasonable with standard battery packs.
Your biggest problem, if you get this stuff made, is size. You will be hard pushed to match the commercial gear for transmitter size.
Just as one more possibility, audio bugs for spying/PI work could be used. Talk to a PI company if they could rent/sell some reasonable units. The gear made for this stuff is expensive, so look at gear made for other stuff thats similar. :)
I use to have a funny sig, but slash cut it off, and I forgot what the punchline was.
What type of recording are you doing? Voice? Instrumental, etc.?
What type of audio quality are you looking for? Sorta goes back to voice, intstrumental or mixture, but I was thinking more along the lines of bit rates, etc..
These 15 mics, are they in seperate locations (rooms or distances greater than 1 Km/Mi)recording seperate audio (multiple sources not intended to be mixed together)?
Is this a live broadcast, a live broadcast with an archive or just an archive?
Without answering these, it's really hard to decide how much you should/could spend and/or what technology you could/should use.
If Chaos Theory has taught us anything, it's that we must kill all the butterflies.
So. You need to record 15 things, without using too many wires.
Yeah, it'd be neat to use VOIP protocols like h323 and g711. But they're not robust, at all, by design. In intended use, if a network glitch trounces on a VOIP-transmitted spoken word (which happens fairly often, in a delicate balancing act between latency and fidelity), the other party might say "Could you repeat that?" In a recording enviroment, you have no such capability; the glitch is forever.
Additionally, there are no facilities that I'm aware of in common use which permit synchronization of multiple h323 endpoints. In other words, this means that the longer you're recording, the less well-synched things become (if you even manage to get them synchronous to begin with). After a couple of hours, you could well end up several seconds off.
Oh. And the codecs aren't so hot, either. Think 8KHz sampling rate, 64kbit/second maximum bitrate, and uLaw encoding. This is fine for telephone audio, but not for a $25k gig.
Ok, so it's not so neat to use h323.
And, don't get me started on 802.11/a/b/g. You're a fool to use this stuff for anything serious, as things currently stand - especially something serious with hard bandwidth requirements.
Why not do the old-skool thang? Buy/borrow/rent/steal a pile of decent wireless mics. Use whatever your local pro sound rental house suggests after you engage them in conversation about what, exactly, you're attempting to do here.
There's only a few considerations with wireless mics:
Make sure you can actually rack a lot of the recievers near eachother - oftentimes, the tuners go apeshit when in close proximity to eachother. If in doubt, try it beforehand.
You don't want dropouts, but you -really- don't want to hear the 500,000W AM station a few miles down the road.
And, make sure you're using the correct mic for the application. Since you're so fucking vague, we've got no idea if you're recording a press conference, a touring band, or the mating rituals of the Australian wolfhound. (Do you even want anyone's help?)
Oh. And many wireless recievers include some fashion of high-level output, suitable for driving a tape machine directly. You can avoid mixer rentals by using gear in this way, if dollars are tight. (OTOH, if possible, a good console and headphones to tie everything together will save numerous headaches.)
Speaking of tape machines, you need some kind of recorder. You can use a PC and a multi-channel pro-oriented sound card, but they're relatively unreliable - especially on the move (which you may or may not be - it's impossible to read through your obfuscation).
Instead, try multitrack tape. You've heard of it before. Modern nomenclature tends to sound something like "ADAT" when spoken. Such machines are common, cheap, and come in 8-channel chunks. Which means that you'll need two of them, and a toslink cable to keep their clocks synched.
Alas, ADAT is limited to 45 minutes or so per tape. This may limit your possibilities, or it may just mean that you need four machines in linked pairs in order to switch seamlessly to a fresh set of tapes.
Whatever the case, don't reinvent the fucking wheel for one gig. This is -just- analog audio here, and only 15 channels of it, at that. Don't make it any harder than it should be, especially if it's detrimental to the work (see paragraphs 2, 3, and 4.) Furthermore, if you're having a hard time understanding anything I've written here, find someone else to do this project for you; you're simply unqualified.
Kid-proof tablet..
Hmm looks like the wireless phone isn't on their site. Here's their hard phone and you should email them if you want more info on their wireless device. I know it exists. I have a spec sheet and have tested with it.
Wireless mic needs should be less than 5 for most stages. I worked for a church which incorprated only 2 wireless mics.. One lapel and one handheld. The lapel was used by the preacher in combination with a pulpit mounted lightwight gooseneck mic. The handheld used by the choir director to pass to guest soloists and used in audience discussions. We also incorprated a left stage mic, right stage mic, a right and left front stage mic and 2 hyper carnoid choir mics (phantom powered, works with only certain boards but there are adapters)
You should consider Very high sensetivity hyper carnoid mics suspended above stage areas. These little boogers can pick up interesting whisper conversations from a choir. We used 2 of these mics for a 25 foot wide choir section. They were also able to pick up people who couldnt get their wireless mic to work, if your sound tech is good enough he can pull enough from one of these mics to at least let a monolog speaker be somewhat heard even with the mic behind them 5 to 9 ft and 8ft from the ground.
You really should tell us what production you are doing, and a few of us ex or current audio techs can tell you what we have done.
I have also had my hand in doing all string instrument band concerts, choir contatas, school and church plays and several rock band concerts.
If I were to use wireless mics, i would at the most use 4. 3 on stage (lead, left, right), and 1 for MC-DJ all handheld design (though I dont consider the left and right singers to really need a wireless, the lead needs it the most). If a band member wishes to use a wireless with their guitar, they may provide their own barring they can find a free frequency. I will not provide a wireless for a guitar-bass or otherwise as latency comes into consideration (been there watching the band member play and come back a moment late, bad situtation tho, the soundboard was like 200ft from the front lots of latency)
DRACO-
Consider yourself blessed if you are sneezed on by a dragon and only get wet, it could have been a fireball.
They're called Cell phones. VoIP will be somewhat useless beyond the range of a local transmitter. You would get the same or better results from a cordless phone and it would cost a heck of a lot less. If someone started using UWB maybe.
Sorry about the writing. Robot fingers, you know? Cliff Steele in DOOM PATROL #23
You did not tell the business need - do you want to record a music CD (musical, etc.) - or just archive a podium discussion?
For the latter you could try DECT cordless (headset?) phones and a base station that supports conference.
But for music you don't want to use any of the VoIP codecs. If you want to record and do decent mixdown you'll need raw audio - preferrably 24bit @44.1kHz. Plus analogue compressor/limiter in front of the A/D to prevent digital clipping. Plus mini-PC for network connection plus WLAN infrastructure.
So I assume the oldfashioned way will be much cheaper, smaller and easier to handle.
Second thought: do you really need wireless? Maybe you can fix some of the people enough to be cableable.
Maybe you can even record them overall in artificial-head-type (or) at a distance instead of close-miked. This way you only need 2 (decent) cabled mikes. May be a problem with (loud) audience, though...
Get some of those cool cell phones that advertise with Crystal Clear Voice technology, call a land line hooked up the recording equipment.
Would it work? Probably not, just use wired mikes save the money. or even use less wired mikes that will pick up a group of singers and give individual miked to the soloists/important people
-- Tim
TKrabec Pahh
Bandwidth would not be a problem if the device could store and transmit it when it or the network had time.
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Search terms in google three of them:
Leave + and " intact.
+"digital audio recorder" +2hrs
+"minidisk recorder"
+"CD Recorder"
http://www.thespystore.com/digitalvoicerecorder
I don't know these people, they popped up on google. Looks excellent though for 99 bux
USB to pc.
That's just the first one on the page.
You'd have to get specs.
If you want to burn to miniCD, you click here
http://www.sonystyle.com/is-bin/INTERSHOP.enfin
Full CD
http://www.epinions.com/Marantz_CDR300_Supers
I'd go on a Vegan diet but the delivery time from Vega is too long. --brownkitty
VOIP and related technology use loss-full technologies. That is, the sound quality will be degraded when using the to transmit, in favor if better bandwidth utilization.
I wouldn't rely on 802.11x giving you the bandwidth that you need either. But if the current budget that you're looking at is $25000, you could adopt a more versitile solution at a lower cost.
That is, you could purchase a single-board computer with an integrated ethernet card for about $400, a good sound card for about about $200, a large notebook hard drive for about $100, and then a few hundred dollars on a decent mic.
Each system would record one audio track as a cost of $750-1250 each. They would all operated independently, and at the end of the session they could easily be connected (via ethernet or 802.11x) to a central server for mastering. That way you don't have to worry about the bandwith. With a 40GB hard drive, each system could record quite a few thousand hours of audio without any loss of sound quality.
It is a small conference style setting, however wired mikes are unsuitable as the people involved will be moving around a lot. Distance will be small, no more than 50m from base units.
I have already looked into renting and this is good for a while. However this program will last for about 2-4 months with multiple sessions each week so renting will quickly become more expensive than buying. It is also something that will occur on a yearly basis and they want the equipment ready for use at any time.
Mini disc would be suitable but I also have considered the problem of more stuff to break. A wireless system has just as much stuff but a hell of a lot more expensive. Something like the Creative MUVO would be great, cost wise anyway, but after finally tracking down someone who sells these and could answer any questions beyond "Is it cool?", it does not appear to have live recording capabilities.
some replies.
Are you quoting Australian or US dollars? The quotes I have for mike and transmitter start at around $800(australian) for a low end unit(mike and transmitter). About $1100 is the price (Sennheiser EW100, recommended after asking around) for a reliable unit with a broad range of selectable frequencies suitable to prevent crosstalk, digital UHF I think. As for the 100+ channel receiver this is about the price I was looking at, however while they can receive 100+ channels they can usually only process and output about 8 channels so I would need 2. Plus the recording equipment about $5000 for 16 track mixer/recording unit capable of spitting out a multi track audio cd at the end of the day, no PC needed. I haven't included possibility of bulk discount. Also the people running this particular program have little technical skills so something that does not have to be baby sat the entire time is needed, this tends to drive up the cost a bit.
A recent addition is the capability to scale up even further.
Typical and totally wrong, but still a funny and deserved response. If someone has the knowhow and ability to make a system along the lines of what I need, and preferably local, negotiations are a possibility and I can redirect you to the people who want this. The project is only really in the "What can be done?" stage so it may not even go ahead in this way.
Thanks to those that actually read my post and gave an inforative response. I guess wireless IP just is not mature enough for my needs. Would make a good reseach topic for some comp. engineering student though.