I've read the postings on this but have a few more questions.

I'm recording an event this weekend that will have 5 people at microphones, and the theater has a house PA system. But I haven't been able to speak with the A/V person, and don't know what kind of board they have, etc.

So essentially I'll be winging it. And I'm not exactly clear on everything that's involved.

I want to attach a feed from their board to a spare video camera in the audio booth to record the audio. I'll then be free to move about with the main camera.

The camera has both XLR and RCA inputs.

I'm going to buy a Passive Direct Box. These allow signals to flow both ways, yes? I've read that they can be used to connect low signal guitars to the high signal boards. But they'll also connect the output of high signal boards to my low signal camera, correct?

I also understand that they have several types of connections; XLR, RCA...so I'll take along an assortment of cables and male/female adapters...

I'm also worried that their XLR may be wired differently than my XLR, but I'm not sure how to test that? and can hooking up a differently configured XLR damage anything...their board or my camera? are there some type of "crossover" adapters available?

Should I get some XLR to RCA adapters? RCA to 1/4"???

any other tips for "going in blind"???

thanks :O

any and all adapters you can add to your kit will help you adapt, however you need to make sure you attach only adapters that will not compromise the original signal.

A direct box even a passive one is not made to convert to +4 balanced line level but is designed convert a instrument level or line level ( -15 to -10 roughly) to microphone level which traditionally sits at about -30db they are NOT designed to bring XLR +4db line level down to -10 consumer line level.

what you ideally need is what is called a splitter preferably an isolated splitter as the sound guy will not likely let you interrupt his main feed with anything that could compromise what he is doing.

but having all these things in your kit will keep you prepared for more situations as they pop up.

more than likely the sound guy will have an available feed that he can probably give you if you coordinate with him or her. this is where your people skills come into play. but be prepared to adapt whatever his board may have to your camera (this is where a DI would work great if he only has line out -10 consumer, this can give you an isolated mic level feed to your camera) or you can simply adapt it to RCA that you say your camera has.

good luck, hope this helps a little

GG

"be prepared to adapt whatever his board may have to your camera (this is where a DI would work great if he only has line out -10 consumer, this can give you an isolated mic level feed to your camera) or you can simply adapt it to RCA that you say your camera has."

So if the AV tech says "I have this output for you to attach to", how do I know what level it is? or what level I need?

Do I always need to connect to the board through a transformer-type DI to keep the electrical systems separate?

I don't mind using the RCA connection. Would most (?) boards have an "RCA out" that would be the correct level? or do I need an RCA inline attenuator ???

I'm going to set a third camera up with a shotgun mike pointed at a house speaker - just in case nothing else works.

thanks for your reply

Why record to a spare video camera? A purpose built audio recorder should do a much better job. The audio sections of video recorders typically leave much to be desired in the quality department.. If that's all you have then go for it, of course, but you might want to consider adding a dedicated audio recorder to your kit at some point.

Aside from the other good recommendations above.

"So if the AV tech says "I have this output for you to attach to", how do I know what level it is? or what level I need?"
> 1/4" TRS outputs will likely be of the +4dB level. Your best option in that case is to have a 1/4" to XLR adapters or cables, and set your camera to 'Line'. Using a balanced line level signal can offer very long cable runs without issue. NOTE: (although the output is referenced to +4dB, the actual output may be lower depending on how the mixer is gain staged.) If you experience a ground-loop hum, use your DI.. most DI boxes have a 'ground lift' switch for those instances. An RCA connection is normally referenced to unbalanced -10dB, in that case, the cable going to your DI should be short and set camera or other recording device to 'mic' level when inputting from the DI.

"Do I always need to connect to the board through a transformer-type DI to keep the electrical systems separate?"
> Not always.. refer to above.
FYI: It's usually best to power the recording device from the same A/C circuit as the house PA, avoiding ground-loop issues in the first place.

"I'm also worried that their XLR may be wired differently than my XLR, but I'm not sure how to test that? and can hooking up a differently configured XLR damage anything...their board or my camera? are there some type of "crossover" adapters available?"
> Most XLR's are wired the same these days ( once upon a time there was a discrepancy on some equipment as to which pin.. 2 or 3 was the hot = +. Pin-2= hot, has been the standard for quite a few years now so you needn't be too concerned if your XLR cables are wired the same. You do have a some way to test your cables... (Pin-1 to Pin-1.. (ground/ cable shield) -- Pin-2 to Pin-2 --- Pin-3 to Pin 3.
NOTE: Even if Pins-2-3 were reversed, it would cause no damage.
FYI; 1/4" TRS > XLR cable or adapter should be wired to use the following pin allocation:
- XLR pin 1 - to 1/4" TRS Sleeve (ground/ cable shield)
- XLR pin 2 - to 1/4" TRS Tip
- XLR pin 3- to 1/4" TRS Ring

Robert,

Let me try to make this simpler.

To start off, you should never presume to touch or otherwise jack into house sound equipment yourself. That’s the job of the FOH (front of house) mixer. His or her job is to route the board signals to the appropriate ports and set them up for you.

Next, there are 3 basic connector types that show up most on common sound boards. XLR connectors, 1/4" phone connectors, and RCA-style line-level connectors.

Deciding which to feed to you is the board operators option. You can “request” what you want — but some or all of the available choices may already be in use for other purposes so the reality is that we video folks have to take what we can get.

So the smart videographer who wants a clean board feed comes prepared with all the necessary “problem solvers” in hand.

Here’s what I traditionally carried to gigs where a board feed was likely.

(ITEM 1.)
A pair of quality 25’ XLR mic cables.
These are commonly terminated in an XLR-M (male) connector at one end and an XLR-F (female) connector at the other. With these two basic cables you can set up your camera up to 25’ from the board and take a feed to two camera inputs.

ITEM 2.
A pair of 12” to 24” ¼” stereo Male to XLR-Female patch cords.
These turn one end of each mic cable into a ¼” phone plug which is what most “music oriented” mixing boards like to see. This lets the board operator give you a feed from various common patch points including AUX outs, AUX sends, and even Channel Inserts if necessary. If you’re working with an experienced board operator, request these as “pre fade” sends so that gain adjustments at the mixer don’t effect your feed. These should be "balanced" adapters with at least 3 separate connection pins or rings at the plug ends. Two segment plugs do NOT allow for a balanced feed, but a 3 conductor plug works just fine with a 2 conductor unbalanced signal.

ITEM 3.
A pair of switchable XLR Barrel Pads
These will reduce a line level feed down to mic level. The best ones are switchable with various stages of perhaps, 10db, 15db , and 25db or similar. This lets you take a line level feed, and pad it down to a signal that won’t overdrive a mic input at the camera. (If you have a MIC feed, but your camera requires a LINE level, you’ll need signal amplification and that typically means you need to add a powered mixer to your setup.)

ITEM 4.
A quality, well-shielded 10-20 foot (or so) RCA stereo patch cable. If all the sound board operator has available is a “tape out” send, this will let you tap into it and use the RCA Female to XLR-M adaptors below to feed it to your camera inputs.

ITEM 5.
A pair of RCA-F to XLR-M adapters. This lets you direct-connect the RCA cable to the camera’s mic inputs (using the pads if necessary, some cameras may have direct RCA audio inputs to the tape, but many do not.)

Occasionally useful but less "necessary" are:

ITEM 6.
A pair of XLR “Y” cables. (each one an XLR-M to two XLR-M’s which will transform a mono board output into TWO feeds one for the original house feed and one for your camera – but most sound engineers don’t like folks putting an extra load on their “main outs”, so this may just gather dust in your kit. I think I used mine maybe twice in 15 years of my prime working life - most commonly in places like high school GYMs where nobody’s really in charge and you can get away with it.

ITEM 7.
The final “useful” item would be a couple pairs of XLR “gender changers” which are nice when the house guy drops you a line and you’re expecting it to be terminated in one gender, but it actually ends in the other gender instead. (trust me, it happens more often than you think!)

If you have this equipment in your kit, along with a camera that lets you adjust the microphone levels properly, you should be good to go in most “house feed” circumstances.

This is not a “comprehensive” list – just a good basic start on a problem solving “tap the house board” sound kit.

Hope this helps.

Good luck.

Bill, you get the "nailed it" post award for the month. With those tools, a recordist can take anything off a board. The only way you could fail is if there are no free outputs, or if the mixer tells you to get lost.

Control everything you can control. And dont sweat the stuff you cant

Bill, you get the "nailed it" post award for the month. With those tools, a recordist can take anything off a board. The only way you could fail is if there are no free outputs, or if the mixer tells you to get lost. ...

And it should be noted by our OP that the latter eventuality is always possible and he should plan for a backup strategy accordingly. The FOH mixer is there to provide house sound for the audience and anything he provides to the videographer is done purely as a courtesy. He is perfectly within his rights to tell the videographer to eff off. So come prepared to record without receiving a house feed at all, treat him nice and offer to buy him a beer after the show.

Thanks again for all the great advice!

The only thing I would change in Bill's post is Item #2 would be more useful in the OP's case if they have male XLR ends. That way it would be the proper gender for being a 1/4-inch output cable from the board to an XLR input on a camera or recorder.

Hey, it was a long post.

If that's the biggest case of "gender confusion" I have in my life, I'm OK with it. ; )

(Also, now you can see why I recommend carrying both F/F and M/M XLR "gender changers" with you - sometimes what you think you're thinking isn't what you think to ask for in the heat of setup!)

Peace.

can someone explain what the difference is between these two "direct boxes"? If I wanted my camera's XLR fed by a 1/4" feed from an audio board?

GuitarCenter (http://www.guitarcenter.com/Product/CompareItems.aspx?prevurl=http%3A//www.guitarcenter.com/Direct-Boxes-Signal-Processors%2CNew-Gear.gc)

thanks

My suggestion for house sound "DON'T DO IT"

The only two times I would have been burnt is taking a feed off the "sound guy". If it hadn't been for my backup I'd been in big trouble.

I found the best way is to ask the "sound guy" where a "sweet spot" might be that you can set up a wireless lav and feed the signal directly into your cam. I have dropped lav mics down from the balcony very near the sound guy and got great sound.

I would also recommend a totally separate sound recording (backup).

can someone explain what the difference is between these two "direct boxes"? If I wanted my camera's XLR fed by a 1/4" feed from an audio board?

GuitarCenter (http://www.guitarcenter.com/Product/CompareItems.aspx?prevurl=http%3A//www.guitarcenter.com/Direct-Boxes-Signal-Processors%2CNew-Gear.gc)

thanks these two "direct boxes"... What two "direct boxes?
GC page: "Compare Another Item"

Sorry - guess that page went away. the two direct boxes are:

Live Wire Solutions SPDI Passive Direct Box with Attenuation Pad and more Direct Boxes at GuitarCenter.com. (http://www.guitarcenter.com/Live-Wire-Solutions-SPDI-Passive-Direct-Box-with-Attenuation-Pad-103814505-i1372940.gc)

Live Wire Solutions PDI Double Shielded Heavy Duty Passive Direct Box and more Direct Boxes at GuitarCenter.com. (http://www.guitarcenter.com/Live-Wire-Solutions-PDI-Double-Shielded-Heavy-Duty-Passive-Direct-Box-103686903-i1372939.gc)

thanks

Robert, you don't want to use a direct box as a go-between from the mixer to your camera.
A direct box is a musical instrument interface, for converting an electric bass guitar signal for example, to a balanced signal into a mixer.

Bill Davis has given you a very good list of what you should have in your bag.

Good Luck!

Dave

David is certainly correct, you do not absolutely need a DI... however if I where anticipating patching into an unknown system, I wouldn't leave home without one. ( and for that matter an IL19 iso, but that's another story)
Which DI Robert? Surprisingly, the cheaper Live Wire Solutions SPDI DI model has an attenuator and would most likely be better for A/V production. The more expensive model appears to be of heaver duty build and shielding, but with no attenuation.
IMO, the Rolls DB25b is an even better option with a variable attenuator, and is a little cheaper. All three have ground lift switches, which is a 'must have' feature, and standard on most DIs.
NOTE: If buying a DI for musical instrument purposes, I would recommend an active DI, like the Countryman Type 10, a long-time favorite among pro players and engineers.

Message deleted again, sorry. PC issue, NOT GOOD

I had spoken with the location AV guy last week, and he told me No Problem, they'd be able to hook me up - any type of connection I need.

Well, the event was yesterday, and the AV guy didn't show up till the last minute... and then said he was too busy to hook me up to the house board.

So I ran a wired mic to the podium for that part of the presentation. As for the rest of the house mics, luckily the AV guy was able to record his house feed on CDs, which he gave me afterwards.

Now, if I can just sync them up with the video, I should be okay.

It doesn't matter how much you plan, there's always something...

Thanks again for all your suggestions!

Another good problem solver to have in your kit is the Ebtech Hum Eliminator. It isolates from ground loop hums and converts to or from balanced to unbalanced in either direction. It doesn't change the signal level like a DI is designed to do, and is primarily for line-level to line-level connections.

And yes, there is always something unexpected that is likely to happen. If you have a couple of alternate plans in place, always including your own independent equipment, you can usually deal with a problem and get a satisfactory end product.

A "direct box" has almost no use in a video production chain.

It's function is to bypass the "amplifier stage" that is typical in a live music performance where guitar or other instrument is plugged directly an amp. A microphone is then placed in front of the amp - and that mic level signal is sent to the mixing board.

A "direct box" bypasses the mic/amplifier and simply feeds a musical instrument "directly" into the input of the mixing board matching impedance and level so that the instrument signal "looks" like a mic to the board input.

All audio for video is concerned with the OUTPUT of the mixing board - and routing it properly to the input of a recording device.

No "direct box" needed.

Of course Mr. Davis is correct that a Direct Box is NOT the right tool here. However sometimes that is all we have in the role of "isolation". A proper isolation transformer (such as the Ebtech mentioned by Mr. Massengill) would be the correct solution.

A direct box is better than nothing when you need some isolation from an unbalanced source into a mic-level input on your camcorder, etc. In exactly the same way you can hammer a (small) nail with a wrench.

Bill Davis's list is pretty much spot on... When I'm mixing shows and a video person show up and has even half of the gear he has listed, I'm happy to help out. When a video person shows up at the last minute, doesn't have any cable or connectors to interface *their* camera, I tend to not want to help.

I would usually suggest a couple small changes to what he listed-

1. XLR cables longer than 25' are a good idea. 25' can be consumed easily just moving around a console.
2. Consider a 2 pair cable/snake. When I'm shooting, I'll bring a 2 pair snake with me to make it easier to run audio. I have several of these- a couple are standard snakes with 2 full lines in them. A couple are what I usually refer to as duplex cables. Take a piece of star quad cable (4 conductors plus a ground) and have it terminate in a 5 pin XLR. From there, you adapt out from the 5 pin to a "Y" with 2 standard 3pin XLRs. Ground is shared between the two lines. I've run over 100" with this cable without issue and the advantage is that it is a single thin cable so it is easy to route, tack up over doors, etc...
3. If ground issues are a concern- especially if a lower end console is used that doesn't have balanced outs, get a pair of these: LINE BALANCER/SPLITTER - Catalog - Whirlwind (http://whirlwindusa.com/catalog/black-boxes-effects-and-dis/specialty-interface-solutions/line-balancersplitter) You can get multiple functions out of it- split to multiple cameras/locations, balance a line, ground lift, hum removal, etc...

I've used DI's plenty of times to do a similar job, but it really isn't quite the right tool. If you do use a DI, use passives, not active DI boxes. Be aware that your input level will almost certainly go down from Line to Mic. Also, listen to your signal- if you are hearing distortion, make sure the buffer on the DI is engaged. You may be overloading the DI.

--Ben

Told ya about house sound ... "Don't do it"

Now your worried about sync with the audio C/D ... I would be too !

Wow...why didn't you send a wireless lav signal directly into your cam?

SIMPLE AND YOU CAN MONITOR THE SOUND ON THE FLY

Happy ending - the CD audio sync'd up fine and the project was a success.

A wireless would have been nice, although I've run into problems with wireless interference.

I'm looking at a digital audio recorder that I can feed wired mics into!

I've used a VHF wireless system to hook into a headphone monitor jack on the mixer (friendly with the mixey folks)... Stereo > Mono adaptor into my wireless setup. This allowed me to capture synch sound throughout my gig... I even got to set the levels on the headphone out to hit my meters right :)

I've used a VHF wireless system to hook into a headphone monitor jack on the mixer (friendly with the mixey folks)...

Scary thing about doing that though is if the sound guy solos a channel at any point, that's all you get on your feed.

I've done it (and it's a good reminder) but I'd suggest that is a LAST resort and would only consider it as a backup to another source that is "guaranteed"... like a room mic.

Yes, most systems with an operator would need the headphone freed up for soloing or other purposes. with a set and forget system in hotel meeting rooms and such, I suppose that would be ok, but in either case I would opt for a main or sub feed, or better yet, a prefader aux send, which the least likely to be fiddled with.

Having just tapped into a theatrical house PA (it was offered by the house) I have a few bits of something to add.

1) Expect large houses to have some sort of feedback preventing delay in the audio. Usually one frame or so. The reverb will be apparent when you play back your video with a camera or room mike mixed in.

2) The PA mix is for the house not television so don't expect everything on stage to be in the house feed in anything approaching a usable mix. I did camera on a concert once and the house audio tech offered to so a multitrack recording of the band but forgot to assign the tracks before it started. We ended up with with eight identical house PA tracks which were minus the drums and the bass (which had it's own stage amp). The room mikes were not good enough and the project never went into edit. The theater pice we just filmed had a couple of singers who could fill the room without amplification so the tech turned them down on the house PA. Fortunately the room mikes were able to get them with decent quality and I could mix it into the edit.

3) I find that a portable mixer is the best solution as it gives me the most ability to adjust the house feed although an audio kit is the better in situations where a mixer is too much to deal with.

One has a double wound transformer, so the ground lift leaves the earth intact, but provides insulation between incoming and outgoing grounds. The other is the more usual type that simply lifts the ground, relying on the ground the other end. I'd be happy with both.

A DI box is pretty useful, because if you want a mic level signal from the board, then how else will you get it from line level sources?

Quality wise, a direct board feed is better - when mixed with the room sound.

The frame or so delay in digital boards is a necessary function of analogue to digital coding and decoding - it does have a small benefit in feedback reduction. The only other delays are usually provided externally in the speaker management systems, not in the mixer - so what you get from the board is as close to aligned as is available. The distance from the stage to the cameras usually matches or is worse than the latency of the mixer, even digital ones.

NEVER trust the board op to keep your feed balanced. They won't have the time or inclination to do it. At best you will get a mostly balanced feed - but it won't be perfect.

A DI box is pretty useful, because if you want a mic level signal from the board, then how else will you get it from line level sources?

The traditional/original meaning of "Direct Box" was a device to take the very low level and very high impedance unbalanced signal from an electric guitar and transform it into the low impedance balanced signal we expect from microphone sources. Direct boxes are not really suitable (or designed) for taking line-level signals as an input.

The way to get a mic level signal from a line level source is to use a pad. Some direct boxes may include a pad feature, but that is not their primary job.

It is also very likely that you need isolation from the house system, so a transformer is typically used. Again a DI box may include this feature, but that is not its primary job, either.

However common use of the term has been degraded to the point where "direct box" could mean a number of different things.

I have several of these Rolls DB25 "Matchbox" units and I like them a lot:
Rolls Corporation - Real Sound - Products DB25 Matchbox (http://www.rolls.com/product.php?pid=DB25)
They have a good size real isolation transformer along with a 0-20-40 dB switched attenuator and a switched ground-lift.

Yes I would agree with Richard. And yes the DI was primarilly for musical instrument interface, however the passive one often loaded down acoustic/electric guitars and such. I also have a Rolls as well as a few IL19 iso's and in-line pads. Incidentally, the latest Roll, the DB25-B (I think) has a variable attenuator which is great for more precise gain staging

Yes, the Rolls DB-25 b model does have a variable attenuator although some sites still show the old photo or even have the old description. I got two of them a couple of years ago right after the change was made so most vendors should have the b model now regardless of the description.

In what situation would you ever need to use two of the Rolls DB25B at the same time?

I'm not sure I could name any device that I own where I don't have two of them... Some days I have multiple setups on location in different corporate buildings at the same time and move from one to the other as needed with no time in between for moving equipment.

Even in a single setup there could be a need for different balanced signals to be routed to various recorders or cameras from multiple unbalanced outputs. If the recorder or camera has mic-level-only inputs, a pair of DB25b's is less expensive than a two-channel Ebtech Hum Eliminator plus external pads and adapter cables.
Some of my setups need routing to a PA system, telephone interface, two cameras, computer with screen recording software and a backup audio recorder simultaneously. There's always some need for adapting, padding, balancing and breaking a ground safely.

And there's that fellow Murphy who likes to show up unannounced.

Not sure I agree with limiting the use of DIs to guitars - they're an invaluable tool for any on-stage job where it's necessary to convert hi-z unbalanced to low-z balanced. Most of the popular units have a number of available preset gains - with some even coping with loudspeaker level (although they're rarer).

Both pro-level and hi-fi level kit such as MD/CD/DVD/Computer outputs etc etc are perfectly suitable for the popular DIs (I tend to use the BSS ones myself) where the key factor is getting a balanced output. Level isn't a problem. Most designed for broadcast or live sound are extremely tolerant of high input levels, and the transformers (or electronics) are built to cope. It's rare, apart from on bass guitar to DI the feed from the guitars as most players use stomp boxes or other processing, which has a proper line level unbalanced output - and this is what the DI boxes sniff. Now many bass players use processing too - the old purpose of the DI box is changing, with the industry tending to use DIs simply as a convenient method of getting line unbalanced into something with an XLR socket!

Here in the UK transformer isolators are not very common. I've got one in the box somewhere, but I use the BSS DIs on all things really. The 133 has a 40dB pad for speaker connection, and an input impedance of of 1Meg - so isn't a load on sensitive single coil guitar pickups.

The 133 is the latest version of the old 116 which was extremely popular here for years and still give good service. If somebody wants a mic feed from a venue sound system of unknown type, then a DI is a perfect method to provide a mic level balanced signal from the common outs. Some desks will have +4 XLR balanced outs, but frequently, they're too hot for the pads built into popular cameras - people with Sony XD-CAM always say less level - and end up with a fader maybe an inch off the bottom - the gain structure is all wrong - they pads on the Sonys seem too much, or not enough.

A pair of decent DIs are a perfect solution, and I can't understand why US practice finds this a problem. Here, DI boxes are amazingly common in everyone's toolkit - as generic problem solvers.

ALL the current popular DI boxes offer solutions to ground loops, by either lifting the ground, or using a transformer with two windings but no common connection. Very few, apart from budget versions are without pads. All the cheap ones use transformers and only the more expensive types have electronically balanced outputs, and use phantom for powering (often with a battery option).

The current usage of 'DI boxes' is at least 30 years old - the time I bought my first one. It's possible we have a UK/US language problem, but checking the popular manufacturers websites, DI is a common term and I'd even go so far to suggest that what I've explained above is the standard for anyone who needs to connect unbalanced Hi-z to balanced Low-z. People like Alice and others make devices that isolate and in some cases protect, but stick an XLR on the output side and they get re-labelled DIs.

They delay you are experiencing has absolutely nothing to do with the console. The largest latency out there in any PA situation that I know about is the old version of cobranet which has a 5-2/3 ms latency to it. Most digital PA consoles are in the realm of 1-2 ms of latency.

What you are most likely experiencing if you are a frame off is the time it takes for sound to travel from the stage to your microphone. Count on about 1 ms per foot which means that if you are far enough away, you could be approaching a frame of delay (especially if you are shooting at 60fps). The console will not be giving you a delayed signal so you will experience a bit of a difference between the two. This is why I tend to sync audio to video in post by eye- not by matching up waveforms. If the camera is close enough, you can make that work, but more often than not, the delay just won't cut it (especially when you get closeups on fingers and such).

As for the mix being suspect- that is absolutely correct. The job of the FOH engineer is to make sure that the house sounds good- not to provide a good sounding feed to video. If they do, it is a bonus, but not the first priority. When I'm mixing, I tend to set stuff up for getting at least a decent recording out of the console, but I'm definitely in the minority of engineers there. I will check a recording mix on headphones on occasion, but most engineers pretty much refuse to use headphones in any way when they mix.

If the PA situation is one where there is very little acoustic energy coming off the stage (ie the sound is all amplified- say large situations inside or outside), you are much more likely to get a usable mix for your video. If you are in an acoustic space (say a concert hall), don't count on getting a good sound as the PA is usually to suplement and balance what is coming acoustically off the stage (between acoustic sounds, amps, monitors, etc...).

--Ben

That's interesting although I have experienced differing amounts of delay in the house feed not the expected distance of the live mike. As I usually shoot 30 or 24 frames (never 60p) in moderate (600 seat) to small houses sometimes the delay seems to be related to the PA feeds I'm receiving not the speed of sound. The worst was a delay of two frames in a small 200 seat theater until I got the tech to send an Aux feed from the mixing board not the main mix via the PA amp processors (or whatever they had rigged up). I did a little research and found that the latest theater shoot I did, the audio turned out to be routed from the lobby A/V feed which had a delay of 1 frame due to being routed thru a digital A/V switcher. That was how this particular house distributed their main mix audio outside of the theater's speaker system. So even though the house feed should be in sync, it isn't. The point I'm making here is that you can't always rely on the house feed and frequently the house staff are interns or students who do not understand how their systems (audio, lighting) work outside of a regular in-house performance.

The four big concerts I worked on where the performances went to DVD for commercial sale, we had a completely separate audio system with a qualified audio crew in place to record the music. The house sound was not reliable for this although both systems shared the inputs. Expensive but the results were CD quality (which were also released).

Sound travels about 1000 feet per second. An NTSC video frame is about 1/30 of second long, PAL is 1/25 of a second. So for a close approximation, your sound will be delayed by one frame for each 33 feet of separation between the sound source and the microphone in NTSC territory, one frame for each 40 feet in PAL lands..

Thank you Steve. Brain wasn't exactly working perfectly and I was a decimal off when I was looking at distance per frame. Yes, sound travels a little more than 1000 ft per second or a bit less than 1ms per foot. A 600 person auditiorium can easily have you 60-80 feet away fom the stage. Depending on the layout, you could be even further away.

Say you're 80 feet away and you're shooting 24P. That means that the acoustic sound hitting your microphone will be about 2 frames off.

If you are pulling feeds off of some sort of distribution amp- especially one that does video, you can introduce even worse latencies. Most of the digital audio switchers out there have latencies of only a couple milliseconds, but I suppose it is possible to have more.

I would suggest that if you are concerned about sync, that you're pulling from analog outs off a console. The more stuff you go through, the more of a chance of problems.

--Ben

But presumably the microphone(s) (yours or theirs) are located on-stage with the performer(s), not back at the camera. And if you ARE using a microphone 100s of feet away (at a camera location) then it is only capturing ambient room tone and not a primary source.

Speaking as "audio guy" here....

I find it exceedingly rare that the video person has the foresight to place mics on stage. depending on the PA situation, a mic placed on stage may not actually capture a good sound. In any case with a band on stage, the stage sound is pretty poor and the sound in the house is much better. The couple times I have had video people want to place mics on stage, it has been a major problem. Classical ensembles where the video person wants to put a big ugly stand in front of a group (in a room where mics are hung). Or, even worse, a video guy coming in where there are stands in front of the group and they just assume that they can clip their mics to mine without asking permission.

Another thing I see a lot of is the video guy that only wants one side of a stereo mix so they can use their own mic in the back of the hall (speaking of delay and lag issues). There are even times when I'm providing a broadcast recording feed and this happens. It is not a mono sum, but rather half a mix and then a camera mic that is out of time with the stage sound.

Don't get me started on all of the unprofessional things I see on a regular basis.

--Ben

Yes, I was speaking as someone who was doing audio at least a couple of decades before getting into video. In fact my major motivation for getting into video was to try to improve the state of audio for video.

Alas, as a video producer I have seen first-hand how easy it is to think of audio in second-class status behind working out all the video details. But, of course Mr. Maas is spot on with his observation of really deplorable audio recording practices by videographers.

It is one thing for the local news reporter to come in and shoot 5 minutes of B-roll for the 11 PM news, but someone who comes in expecting to capture a whole concert with a single camera and minimal (if any) external audio equipment is just unbelievable. Why do they even bother?

And I find myself more than frequently on one or the other side of the mixer desk. Perhaps I am just unlucky, but most program producers I work with are functionally clueless and useless in coordinating live feeds for video (etc.)