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Old June 16th, 2004, 01:19 AM   #1
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Laptop audio recording - using DSP's?

This will be my first real DV 'job'...

Along with a friend, I am shooting a promotional video for the local Lions club. We will be interviewing and covering an event on July 1st. To raise (chairty) money, there is a yearly rubber duckie race in which people purchase ducks and set them off down a local creek. The first 15 ducks to arrive at their destination are scooped out and the owners are awarded some pretty nice prizes.

I am going to be running a single oktava -> rolls promix plus -> laptop mic in. The mic will be mounted on-camera. I will carry the laptop in a backpack. The location is entirely outdoors and I will probably be very near the creek at some points.

There are many, many audio recording programs out there, and even more direct X DSP plugins. I would like to do some quick research on what I could do to maximize the sound quality. I have read many mentions of "compression", any links that may teach me the ropes?

As for syncing - is drift an issue if I set the laptop to record 48000Hz sound? To sync I was going to press the snapshot button on my camera which produces a snapshot sound out of the speaker and a fake animated closing shutter, think that will do the trick?

If anyone has any suggestions past answers to my DSP query, please post...any tips will help!
Thanks,
Rob
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Old June 16th, 2004, 03:49 AM   #2
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Hey Rob,

I'm not entirely understanding your audio setup since it sounded like you wanted to move around with a laptop in your backpack, but doesn't the Rolls require AC power? I'm assuming that you're running the Rolls aux out to the laptop line in? Also, you've asked some questions that could lead to pretty lengthy and disparate answers, so I'm not sure exactly how to approach helping you out. So, instead of asking you lots of questions to figure things out, maybe the best idea is to try taking a look at the Recording FAQ to see if the info there can answer some of your questions:

http://www.phys.tue.nl/people/etimmerman/recordingfaq/RFAQ.html

Also, here's a good primer on on-location audio:

http://videoexpert.home.att.net/artic1/242mic.htm

If you're going to be moving around and budget permits, I'd consider ditching the Oktava/Rolls/Laptop setup and go to your local equipment rental shop to rent a shotgun mic and field mixer to feed into your camera's audio inputs (if it has them). This lightens your load, simplifies your setup, and captures audio on tape so you don't have to worry about sync. If you have a good shop nearby, the people should be able to help you get totally setup with equipment and tips -- even on a tight budget.

Definitely get your production side situated before worrying about software and effects. Remember the old saying... garbage in, garbage out.

Hope those links help and good luck to ya!

-Harris
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Old June 16th, 2004, 02:21 PM   #3
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Here's another link that could be of use to you:

http://www.recording.s5.com/html/recording_tips.html
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Old June 16th, 2004, 02:43 PM   #4
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Hi Harris, thanks for responding.

The mixer can be either battery powered by two 9V's or through an AC plug. Here is a link if you want to check it out:
Rolls MX54 3 Channel Battery Powered Stereo Microphone Mixer
http://www.bhphotovideo.com/bnh/cont...=174333&is=REG

About the renting, I purchased this stuff as a hobby and to enter local film fests. Also, although I am getting paid, it wouldn't be enough to cover renting equipment.

The setup is a little bit complicated...but I am a computer nerd first and videographer (ha!) second. As I have it rigged now, the laptop would be strapped inside of my bag, closed, with a mouse attached. I have dissassembled the mouse and I set up the middle mouse button to emulate a keystroke. The keystroke handles the record/pause function of the sound recording software.

(side note)
If any programmers are reading this...I am wondering if this is a possibility:
Hook the camera up to laptop via firewire and record only the audio from the DV. The video is still recorded to tape (well, if this was to be done i guess this would be optional...HD or tape). So far this sounds like any DV capture program...BUT the software would be able to detect when the camera was recording (the REC button pressed on cam) and capture a mic/line in device at the same time. I think I have done a horrible job explaining this but it would make (time) syncing a non issue!
(end side note)

Harris, I do have the possibility of recording to my partner's camera...or building a mic in adapter (3000U doens't come with one but you can do it). However, both of these options have AGC, and I am not sure if either does stereo (you can beat AGC by boosting 1 channel super high) plus I do not have time to build the adapter before this event. Since my partner's camera is a lower end sharp, I don't expect it to have good quality audio...so I am almost certain that although still analogue, the laptop is my best bet quality wise. Also, if I record to laptop, I can record two channels - one safety and one a bit higher.

This is a lot of reading, and is exactly the sort of thing I was looking for, thank you Harris. I am still curious about compression, and it is probably noted somewhere within the links you sent me...I havn't had enough time to sit down and properly read through them. Thanks again!

Any critisism, or suggestion is welcome!
Thanks,
Rob
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Old June 16th, 2004, 08:38 PM   #5
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You've definitely got a creative system for capturing audio! :-)

The last link I posted has an entire section of articles on compression. That should give you a clear start on understanding that topic.

If you're intent on using your laptop-based setup, I'd suggest going from your Rolls aux-out to your laptop line-in instead of your mic-in as you may have level/impedance matching problems. Also, make sure you read that article on on-location sound to get yourself started, since following those basics will improve your captured audio far more than expensive equipment and software will. It's really is THAT important.

Good luck and I hope it turns out well for you!
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Old June 17th, 2004, 09:18 PM   #6
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Hey, I'm not up to the level here may be but may I suggest something.

Using ANY laptop onboard line or mic input jack is NO GOOD!

Laptop onboard sound is not good, there is internal interference, etc., etc.

You'll get better sound in the cam, or if you use portable recording device (MD is a cheap option).

If you want to use laptop for the live capture for sure you have to use some kind of interface and go DIGITAL in it (USB or Fire Wire interface). Check out M-Audio - they have very good devices with even phantom power for 2 mics and additional line inputs.
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Old June 17th, 2004, 09:41 PM   #7
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Thanks for the post Bogdan

Quote:
Laptop onboard sound is not good, there is internal interference, etc., etc.
I really didn't think it was that bad...DV has tons of bad stuff going for it...AGC in particular. Also, I am fairly certain that unless you buy a really good MiniDisc player, the output is analogue back to the computer anyway. So then, I have the MD compressing the audio, and then sending it through the same pathway i'd be using if i'd had used only the laptop.

Here is a pretty detailed comparison of the audio chip on my laptop vs an aftermarket creative offering:
"How Good is Laptop Audio?"
http://www.extremetech.com/print_art...a=24327,00.asp

Also i've read up a bunch on noise reduction cleanup. It seems (according to Jay over at DV.com) that you wouldn't be able to use a dead silent noise recording and delete that throughout the audio track because of "aliasing". I believe that the same does not hold true for laptop audio...i may be wrong here...may be entirely wrong!

Oh, and buying another mixer is out of the question...the rolls will serve me perfectly once the mic adapter mod is complete on my camera.

Rob
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Old June 18th, 2004, 12:48 AM   #8
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Rob, as I said I haven't entered the depth you are dealing with. I just happen to use laptop and desktop PC and think their sound system is usefull for the not demanding home user.
I use it for nothing more but IP voice telephone.
The desktop sound has crackles and other nasty stuff happening, while the laptop seems better shielded but still introduces lots of hum. On my laptop if you touch the area close to keyboard this hum minimizes somewhat.

Even the compresed sound of an MD is far higher quality and much much cleaner than any analog captured sound in PC. Have you actually tried to record the way you describe for example sound from your HiFi? Or just voice from the mic? Have you done tests in the room? Could you check the resulting sound on quality speakers or headphones?

The way to transfer music or sound to the PC anyway requires some kind of digital interface. PCI sound cards are prone to interference and the better once cost a lot. Elegant way is using USB (cheaper and can handle fewer chanels at once) or FireWire audio capture device. The later can have more chanels. Even the cheapest you can find (edirol usb) is much much better than using the integrated jacks on the laptop.
I've used Onkyo USB interface with all possible in/outs (analog, opticval, coaxial) and although not on par with M-Audio or other pro brands it gives crystall clear noise free sound.

Anyway do the tests with the set up you have in mind and see how it sounds.

You'll have to edit the sound in post anyway and it will be much easier to do so with clean source matherial. No matter how high grade sw or plugins you use on crappy material you might be no able to recover it.

Hope that helps!
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Old June 18th, 2004, 12:59 AM   #9
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Something more.
On the AGC issue again it's not my strenth but I wonder what are you afraid from?
If you had quite environment the AGC would boost too much but on outdoor event it will more likely protect you. There will be lots of ambient noise and it will keep the recording levels low anyway.

The time I disabled AGC (on my GS100) I had problems with the sound in post but this might have been because of lack of experience.
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Old June 18th, 2004, 01:08 AM   #10
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Hey Rob,

Bogdan actually has a point about most laptopsí built-in audio inputs. If you've got the ESS Maestro chipset for your onboard sound device, it definitely doesn't do the best job at capturing clean audio. The ESS Maestro chipsets, which come stock on many laptops, are notoriously noisy compared to most outboard offerings. Combine that with impedance mismatches if youíre running line-level signal into its mic-in, which causes variance in the frequency response, makes for an audio recording system that leaves quite a bit to be desired. Remember, the article you mention is comparing a consumer grade audio chipset to another consumer grade chipset, not a unit that would be considered acceptable for quality A/D conversion. Iím guessing that you probably donít want to spend any more money upgrading your current equipment set right now (and besides a discussion revolving around ADCís is a whole Ďnuther topic altogether), so letís press on.

Unfortunately, I haven't come across many articles talking about quality of the onboard ADCís on cameras, nor have I done my own tests. In fact, one of the only ones Iíve seen that shows measured performance is from Sound Devices for the PD150 ( http://www.sounddevices.com/tech/pd150.htm). As you can see from the article, the onboard ADC on the PD150 works fine for voice, but is horrible for music. Which brings us to another point. It sounds like youíll be capturing voice on this shoot and I bet just about any digital recording device will do fine at your budget level. So, go with whatís convenient. Youíll ensure higher quality recording by having an assistant position the mic as close to the whatever sound youíre capturing, while monitoring the levels to make sure you donít accidentally clip your mixer or your recording device. (Bribe a buddy to help you out for the day for a couple of beers or something.)

With where youíre at with equipment and budget, youíll be better off focusing on technique than equipment (though, at the least, I still say ditch the laptop/mouse setup and borrow/rent an MD recorderÖ if anything, itíll be easier to handle than your laptop in your backpack and mouse in hand).

One last thing, if youíre using any Oktava mic, be sure you have some sort of windscreen on it and that you have it on some sort of shock mount. Those are studio mics, and arenít designed to be handled in the field, much less exposed to wind while youíre outdoors. If the wind picks up, and you donít have a way to abate the turbulence around the mic, the low freq. rumble could get bad enough that it covers up anything youíre trying to pickup.

*whew*

Okay, that was long, but hope itís helpful.

-----------------------------------------------------

I just read Bogdan's replies while typing this up. He also has a point about AGC. If you're not familiar with micing techniques and have to rely on your own handling of the mic while trying to coordinate shooting video, going with AGC ON when you run audio into your cam may not be such a bad idea. As Bogdan has experienced, AGC actually helps until you learn good location sound recording techniques.
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Old June 18th, 2004, 04:48 PM   #11
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Here is a sample .wav file from the laptop

Wow! thanks for replying guys...but you are really starting to scare me!
I have a friend asking to borrow a friend's MD player...it will record line in for sure it is an older one...not NetMD. However, I really doubt it has a digital input for the computer...that was what i was saying about most MD players that *i* know of...it is another step and if it is passing through the same exact analogue input where it is re-recorded, then it would suffer the same (or more) of the side effects due to the crappy laptop hardware.

So, if I wanted to capture to PC from a reasonably priced MD player, i'd have to buy an external USB input which would convert to digital (outside of the box) plus the MD player itself. I can't afford that guys, I just can't. When I was deciding to buy audio equipment, I chose stuff that I thought i'd be able to carry on to a new camera...XLR mixer and a decent quality mic. I know I could have got more for cheap, but I wanted it done right the first time even if it took me longer to get the full setup that i'd require. Plus, this is a hobby for me.

About the AGC: I am afraid of getting the pumping audio that I have read so many horror stories about. That was a good point about learning the audio though...I can see how it would help in the beginning.

About the windscreen and shock mount: (get ready to cringe) I am currently building them myself. I took a trip to the local home depot and have the materials sitting here waiting to be put together. Although not the best bet, Iíve done a bunch of reading and I think I can make something half-decent. For the shock mount I have a wooden base with two metal hoops. These hoops hold elastic material (havenít decided between rubber elastics, hair elastics, or the round string type...this will be a test and see what's best decision) that suspend the mic. For the windscreen, I have purchased fake fur from a fabric store, and I have cheesecloth, a thick speaker foam type stuff, a wire skeleton, and speaker grill off of an old sony television. I absolutely love DIY projects, so the boom pole will be a painterís pole from the home depot...I saw some perfect ones when I was there last time. Oh, and if my contraptions don't work well enough, hopefully the mixer can help a tiny bit:
"The switchable low-cut filters were down 2 dB at 125 Hz, dropping to -14 dB at 32 Hz, which should control most rumble and some wind noise." -http://dv.com/reviews/reviews_item.j...w/rose1103_rev

the audio sample
Since I do not have my mic or mixer yet, (I missed the delivery of the mic today) I recorded my cd player's headphone output into the laptop's mic in (Harris, it doesn't have line in). The actual audio clip you are listening to is from a film called "Waking Life". I love the movie so much that I ripped the audio and burned it to a CD for listening.

INSTRUCTIONS FOR DOWNLOADING
Sorry guys, I don't have a real host.
http://www.aloofhosting.com/robh/laptop.jpg
Right click, "save target as". Change the extension from .jpg to .wav and press okay. Sorry about the confusion, but the website will not let me host .wav files
Thanks for the incredible amout of input!
Rob
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Old June 18th, 2004, 06:24 PM   #12
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Rob
Try using PVC pipe cut into "hoops" use a hacksaw to cut 8 slots similar to the Audio Technica 8415. Use wide bands if possible. with a little care you could make a nicely finished shock mount.

For those not understanding, Rob has very creatively found a way around a lack of audio input on his camera.

I'll give you a big pat on the back for creativity. I really hope it works out for you. is the race on the Humber? when will it be held?
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Old June 19th, 2004, 01:18 AM   #13
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Hey Rob,

You're doin' a great job with what you've got. The tips and opinions you're gettin' are just from people trying to help ya out, so don't be worried. Remember, none of us would know what we know or be where we are without the help of a bunch of others teaching us and giving us a leg up. Believe me, there's still a lot for me to learn, too, and I use these tools as part of my living!

If I were to prioritize a list of things that may cause you trouble on your shoot that you may be able to mitigate without taking a chunk out of your pocketbook, it would be the following:[list=1][*] Laptop/mouse/backpack setup - difficult to manage; no way of monitoring recording from the recording device and easily adjusting gain if needed on the fly; no positive feedback to tell if you're actually recording audio (imagine the shock of realizing that great interview didn't get recorded); and last but not least, potential for accidently bumping into the middle mouse button while running around, thereby accidentlally starting/stopping the recording -- getting the MD player will help immensely, even if it means playing the headphones/line out through your laptop mic-in[*] Mic wind/handling noise - the DIY stuff you're doing is far better than nothing at all, so run with it and let us know how it goes -- glad you're already thinking about it[*] Technique -- there's a lot for you to juggle here while playing with a DIY rig where you don't have any experience with yet. This is where a lot of amateurs show their badge, but it's also a place where you can start to work on with the time you have before your shoot. The answer is simple -- PRACTICE! Understand the basics of good micing technique (as much as you can absorb in short period of time), and practice, practice, practice... while doing live audio/video recording, with all the equipment rigged up as you would be on your shoot. It's not glamourous. It may not even be particularly fun. You may even feel goofy running around with a bunch of equipment on, taping and recording very mundane things, but in the meantime, you'll be working out the kinks of your self-made rig and smoothing out your handling. Believe me when I say, this is by far the greatest factor in determining the quality of your production where you're at right now.[*] AGC - the pumping effect people are talking about really depends on your audio environment and what you're recording. If you get a chance to do a few tests in a similar environment with a comparable source, do a few runs to see if the audio is okay. If not, you're idea (in your first post) of recording your mono input in stereo, but setting one of your recording gains down for safety is a good way to go.[*] Getting audio into your laptop - the MD player won't be your quality bottleneck in this case, if all you have is the mic-in, then short of purchasing (or borrowing?) an outboard USB/Firewire device, just do your best with running the MD's headphone or line output into your laptop's mic-in during post[*] ADC audio quality - With everything else going on above, don't sweat this one until you're ready to invest more money. Until then you'll be learning a ton to help you move forward and maximize your future investments.[/list=1]
About your audio clip, thanks for posting it, but it doesn't go very far in determining audio quality. I'm familiar with the ESS Maestro audio chipset, since my last laptop was a Dell, which used that particular chipset, including a line-in jack. It's performance was pretty poor in general, though I've always relied on outboard ADC's, so it wasn't an issue with me (I had disabled it in normal use to free up an IRQ). The high noise floor will become even more apparent when you start applying compression in post, esp. on recordings in a quiet environment. That being said, don't sweat it. You've got bigger fish to fry here than the noise floor of your laptop's ADC!

Seriously, you're on the right track. Just keep on moving forward and learning. Pretty soon you'll get to a point where you'll be able to help other people who are starting out.

Good luck with your shoot!
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Old June 19th, 2004, 10:18 AM   #14
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got the mic

Quick update...when i find some time i'll reply further

but I got the mic! and it's TINY! Here is a pic of it, with a paperclip so you can get an idea of the size

(you have to right click, save target as)
http://www.aloofhosting.com/robh/oktava.jpg

Rob
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Old June 19th, 2004, 09:04 PM   #15
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Regarding the laptop

I am just going to suggest something that may not be practical for what you really want, but is more flexible than a laptop. A Shuttle PC or one of the other minis has an expanse slot, even in cases, an AGP slot. The form factor is small, but it would require power and an additional monitor. A cheap LCD could be used and since you are not doing professional edits on it, a cheap LCD would not be a hinderance even if it had a poor color gamut. You could fit almost all of it in a small rolling suite case.

With the expansion slot on some of the units, you could put in almost any of the higher-end audio cards. Also, the whole package would be cheaper than a laptop.
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