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Technical Archives

David Battino

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With 486 comments at last count, our discussion on the Zoom H2 handheld surround recorder is teeming with questions and tips. One of the latest struck me, because I’d been wondering about this myself. Reader Lee Wong wrote:

Help! Does anyone have a schematic they can share for making a really small, portable preamp so I can stick my Soundman OKM II mics in to the H2?

Within hours, reader Gershon responded with this link to reader Trevor Marshall’s home-built preamp. Here’s a photo of the outside; the inside looks nothing like I expected, given the promise of high fidelity. (I won’t ruin the surprise; click the photo below to see it.)

zoom-h2-diy-mic-pre.jpg

Trevor Marshall’s DIY microphone preamp for the Zoom H2 reportedly provides much better quality.

Don’t miss our extensive review of the Zoom H2 and follow-up article on turning its recordings into surround-sound DVDs.

Mark Sigal

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twiddeo.jpg
Instead of telling people what you are doing, show them!

David Battino

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I just got a call from a blind man who liked the sound of my podcast. He asked how he could get started podcasting. Would it require expensive equipment? I told him that all I used was a USB mic and some software. (In my case, Ableton Live, BIAS Peak, and Izotope Ozone, but there are plenty of free options as well.) The secret to my sound, I told him, was upgrading the mic, learning the software, and speaking with enthusiasm.

podcasting-tarsier.jpg

To demonstrate, I referred him to this before-and-after example (516KB MP3), contrasting my voice in the first episode and the tenth. The difference is enormous.

Then I offered to send him links to podcasting tutorials I’d found especially helpful. But when he told me that he uses a screen reader to browse websites, I started to wonder how helpful this background would be. Even if he could make sense of the pages (try clicking the “Listen” link above and closing your eyes), how would he be able to run a graphic waveform editor? I spend many hours cleaning up my recordings, often on a syllable-by-syllable level.

If you know of audio-editing software or techniques that are friendly to disabled people, please leave a link below. In the meantime, here are some of the podcasting tips I assembled for my listener.

David Battino

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A mysterious email arrived the other night. It said, “Please find enclosed two pictures of Midi Controllers. Do you know the make and model of this two units?”

Mystery MIDI controllers

The top one looks like a commercial product; the bottom one looks more homemade, but I could be wrong. Any guesses? Please leave a link. I’m off to browse Analogue Haven.

David Battino

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O’Reilly’s Linux Dev Center just published a fairly technical discussion of how the various Linux audio subsystems work.

linux music

For those who just want to boot up and play, we’ve run several Linux audio articles, including:

Are you using Linux for audio? Let us know what you’d like to read about.

David Battino

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We’re currently wrapping up a review of a high-resolution digital audio recorder for O’Reilly Digital Media. This handheld marvel records in Super Audio CD (SACD) format, and our reviewer has been gobsmacked by the audio quality.

Korg MR-1 top

The Korg MR-1 records at 64 times the CD sampling rate, using 1-bit converters.

Because SACD burners exist only in high-end mastering labs, the recorder comes with software to convert its recordings to more common formats. The idea is to capture archival recordings and then spin off lower-res dubs. Nonetheless, one of the applications Korg suggests is creating "your own hi-def CDs."

That got me wondering—how does the average Joe 44 do that?

David Battino

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This is cool: Simply adding &loop=1 to a YouTube <embed> tag makes the video loop forever. Check it out with this short clip of a Pong-playing watch from Make magazine. (Be sure to click the small play button below the video, not the big one in the center.)

Despite just writing an article on hacking embedded videos, I never thought to mess with the YouTube embedding tags, which are right out in the open.

Jake Luddington, on whose excellent blog I first saw this trick, also explains how to make an embedded YouTube video play automatically. Both his techniques involve removing the <object> tag and modifying the <embed> tag. I’m not sure if there’s any downside to that besides losing XHTML compliance.

David Battino

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I guess I’ve been reading Make too long, but when I wanted to hear Internet radio in the spare room the other day, I quickly devised this wacky solution:

Closet Speaker

The Apple AirPort Express receives the Wi-Fi music signal from iTunes, converts it to analog, and then injects it into the old boombox through a car cassette adapter. The belt raises the tweeters to brighten the sound.

All components were items I salvaged from closets, including the boombox-with-no-line-input, the Old Belt, and the cassette adapter, which I hadn’t used since I’d replaced my factory car stereos.

The AirPort Express had also spent its first year in the closet after I failed to get it working with my non-Apple router. Every few months I’d haul it out, blast it with configuration commands via Ethernet, and then give up in frustration before finally stumbling on the correct settings. (I forget what they were, but it involved lying to the software.)

Here’s a more heroic image of the setup:

Heroic Closet Speaker

Come to think of it, hiding a Wi-Fi speaker in a closet could be pretty fun on Halloween…

Derrick Story

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Keep this in your back pocket… You reset the iPhone by holding down the top power button and the Home button for about 6 seconds or until you see the Apple logo.

David Battino

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NPR did a clever demonstration on Morning Edition this week. To illustrate how much money the 2008 presidential candidates raised last quarter, the announcer played a music clip—one beat of a song for each million dollars. Of course, NPR can’t show graphs on radio, but for me, the audio “visualization” was much more visceral than seeing a bar graph. One reason could be the innate drive to want to complete the musical phrase.

2008 fundraising chart

I grabbed this chart from another NPR story and created a bar for Brownback by dividing the width of the other bars by the corresponding dollar amounts to get pixels per dollar.

We hear “billions and billions” of statistics on radio and TV, but they rarely come alive unless wrapped in a metaphor. Usually that’s an image or a conceptual equivalency, but I think the audio approach bypasses the analytical part of the brain and goes straight to the heart.

Rick Jelliffe

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Grant Richter of modular synthesizer manufacturer Wiard has called for the module-buying public to become less conservative about the kind of front panel material used. “If the public could change their perception of how a synthesizer module must be constructed, we could have a renaisance unlike anything in the past. The single most expensive component in a synthesizer is the aluminum faceplate. There is only one source for turnkey faceplates in the US and they are obscenely expensive. I pay $70 each for 1200 series faceplates.”

Some folks like the blinkenlights, some like the telephone switchboard effect, and a lot of people are still caught in the moment of seeing their first Moog modular, with the wood and metal and knobs and sounds: even nerds could be hippies. Now of course many module purchasers or DIY makers are augmenting existing rigs, they need durability and design consistency in order to maintain their resale value, which may become an consideration as vintage moves into antique.

But for the rest of us, Grant is entirely right, but it is more than just the cost, it is also the time delay and logistics and also the lack of flexibility that causes users problems. Why is it that we currently have the several dozen different form factors for synthesizer modules?

I think there is another way to approach the issue that solves several other problems, especially for the new and DIY maker: adopt A4 (the paper size used outside North America and the Philippines) as the standard size for module front panels. 210 x 297 millimeters or 8.27 x 11.69 inches.

The first question that probably will pop up is Rick are you insane? A4 is about the same size as US letter paper, surely that is way too big? Plus it isn’t an even multiple of any of the current standard sizes…what gives?

Well, lets start off by redefining the problem. DIY people need to buy the expensive panels because they don’t have the skills or tools to cut and make decent panels themselves. But buying in a good-looking panel has a hidden cost: it makes it difficult to evolve and experiment with the module, in particular with anything that requires new knobs, lights or jacks: so new functionality has to go into a new module, which then needs a new panel. Plus if spend your cash on panels, you don’t have a brass razoo for other modules: there is a substitution cost. So Grant is right that the cost of panels is a disincentive to purchasing panels, but it is also a disincentive to incrementally evolving them.

(Update) And high panel costs are a disincentive to make larger panels and more integrated modules, too. It promotes atomism to bring down the price of single modules, but this increases the total cost to users because they have to get more modules for a given purpose. Think of mult modules: the price of these is insane: they have no PCB or circuitry to speak of….a larger panel size with space to space would provide them a free (or at least pre-paid) home.

So how would A4 panels help this? Well, for a start, lets get a view of what I am proposing in more detail, There is some history of larger size panels: the Roland 700 modular had 11″ panels, Serge systems came on 7″ by 11″ panels, and many Buchla modules are quite large. More to the point, the Oberheim SEM modules were 10″ wide.

Larger panels have several advantages. First, trivially, you can fit more into them. You can make different kinds of modules, and pre-patch them, to further save on production cost. Of course, some things need more space: drum machines, equalizers, and so on. I think there is room for a form factor larger than the current modules, but smaller than the 19″ rack size; if the size is accompanied with cost savings and construction benefits.

What started me on this was figuring out the design idea behind the ETI International 4600 synthesizer panel. It is a large wide panel, and I ultimately figured out that it was the same size as four A4 sheets side by side. (Perhaps the transfer for the panel was made on an A1 sheet cut lengthwise?) It is a pretty convenient size, and I have followed the 4600 design in adopting a 5×5 grid. Have one A4 module, and you have about the size of an Oberheim SEM; put two together, next to each other, and you have about the size of a VCS-3, and something that can fit into a 19″ rack with a couple of inches to spare; put three of them together and you have Minimoog width (but longer height); put four together and you have the size of the ETI 4600 or the never released EMS VCS-4, which will match a modern 4 or 5 octave keyboard controller. The Memorymoog is a pretty good example of a synth made from four sections wide enough for five knobs each (the middle two being continuous, and only four rows.)

So why A4? Well, the answer comes down to three things: product availability, development flexibility, and cost. Going to my local art supplies store today, I was struck by the number of products available ready cut as A4: perspex sheets, foam board, plastic, laser transparencies, and all kinds of paper in different finishes. Adopting A4 as the form factor for our DIY modules makes a huge range of possible panel solutions available and inspectable close to hand, and pre-cut.

Of course, we still need to make the holes, but we get a great benefit: because of the lower cost we can be more caviillier about adjusting the layout. We can start with a sparsely populated panel and add more holes as they are needed. Because we are using standard print sizes, we can just print off a new front panel face to suit the new components. When we are finally satisfied that no more changes are needed, then perhaps we could invest in an aluminium front panel, but one reason that metal panels are popular is because of long-term durability (they don’t get ragged) but adopting A4 gives another solution to the problem: it makes renovation easier because making a new set of panels before selling becomes cheaper and more trivial.

Now, of course, you may have access to a nice set of anodized aluminium sheets, along with cutters and drills and so on. But for the rest of us, I think this idea is worth thinking about, because it reduces the complexity of construction. You don’t need to trim anything, you can upgrade and trial designs, you can spend your money on components rather than panels: indeed, because the larger panel size may encourage you to incrementally upgrade modules, it may save you on the cost of sockets too. For example, rather than one small panel each for a VCO, CGS waveshaper, and synced slave VCO, which you habitually use together, you may instead put them all into a single panel, as a super VCO, and save sockets. Or you may put all your VCFs into a single panel with a pig fat switch to select between them.

Here’s the kind of thing I am thinking about: imagine a case wide enough to fit four A4 panels, with top and bottom wooden rails with velcro strips to hold the panels for easy removal, and braces for panel edges so they don’t buckle, if they are made from material that can snap or buckle. A panel might be made from, A4 foamboard covered with A4 vinyl and with an A4 decal applied and acriillc coated. Or it could be clear perspex with an undersheet with the label printed. Initially, it could just be plain printed paper glued to cardboard, even! The equipment cost would be a quarter inch leather punch for the knobs and jacks, and perhaps a 1/4 inch punch for smaller components. No fancy tooling, no precision cutting or bending. You would get something a little like the ETI 4600: this picture shows the kind of size: in particular the oscillators at the far left form five rows of five knobs which is exactly the kind of form factor for one panel.

Erica Sadun

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YouTube has just launched its new TestTube site, which allows you to test out beta features that haven’t been fully deployed. One of these new features is “Replace Audio”, allowing you to sub out the audio track of your YouTube video with a licensed track.

ReplaceAudioC.jpg

Here’s how to do it:

Rick Jelliffe

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Most synthesizer module circuits have much of their real estate occupied by a few common functions:

  • Power supply regulation and decoupling components
  • Input buffers, using op-amps, perhaps with AC coupling components
  • Output buffers, using op-amps
  • Signal converters: dozens of kinds of voltage-controlled resistor-ish functions (for example, using transconductance amplifiers, diode or transistor configurations, vactrols, etc.), and voltage to current converters which may also perform linear-to-exponential conversion (usually transistor-based)
  • If there is to be computer control, then DACs and analog switches

Indeed, the functional core (what is left after the common peripheral functions) can be quite small: the oscillator, waveshapers,filters and logic proper may be less than half the module’s circuits. I see Ken Stone at Cat Girl Synths has this week started releasing some utility PCB designs for some of these common sub-modules.

Its not an entirely new idea: Tellun have their Multi-Use Universal Buffer board.

It is, in a sense, the opposite approach from that taken by ARP in their 70s synths: they bundled their functional core circuits into sub-modules that plugged into a product-specific carrier board which had much of the periphal circuitry: CMS has act-alikes for exponential converter, op-amp, VCO, VCA, VCF, ADSR, noise, balanced modulator, and sample and hold. I am not sure what the design reason really was for these: the sub-modules could be shared between products which would help agility and lower design costs, the sub-module could be swapped out which would help maintanance and upgrades, the sub modules could be potted in acrylic or resin which would help keep competitors eyes out and perhaps have some temperature coupling property, and some components that required matching transistors/diodes/resistors could be built and tested independently of the ultimate product which may help manufacturing and QA.

David Battino

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Podcasting Hacks author Jack Herrington turned me on to a bunch of excellent interview podcasts that I’ve been following ever since. One show in particular, Morning Stories, has a lovely informal feel, and part of the secret is the clever recording technique host Tony Kahn uses. Instead of jabbing a giant mic in the interviewee’s face or forcing him to hunch over one in a studio, Kahn uses a tiny lavaliere mic taped to the brim of a baseball cap.

morning stories hat mic

Morning Stories’ Gary Mott and Tony Kahn record a relaxed conversation at WGBH thanks to their hat mics. Kahn’s initial inspiration was wanting a mic setup that would let him put his feet up.

As Kahn explains in this YouTube video, the hat-mic trick also allows interviewer and interviewee to relax and use body language, producing a more natural conversation.

Podcaster Adam Weiss, whose helpful tip on mic placement I covered recently, lists four more advantages of hat miking on his blog. That prompted me to head over to the Giant Squid Audio Labs site to check out its lavaliere mic selection.

Brad Fuller

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Sophie, a project to create multimedia books, is now available in Alpha release. Based on Squeak, Sophie is available for Windows, Mac and Linux.

Funded by the Andrew W. Mellon Foundation, Sophie is not a tool to render traditional paper books to read on your PC. The Sophie project is aimed to go beyond print and utilize the interactive capabilities of the personal computer. From the Sophie Project site:

Sophie is a digital media assembly tool which allows you to combine images, text, video, and audio into a single multimedia document. It is an easy-to-use program that let’s you put together documents, slideshows, presentations, annotated videos, and more.

Sophie is based on the idea of authoring digital multimedia documents that you can publish for others to experience. It uses standard interface ideas that will be familiar to users of multimedia authoring tools such as Sony Vegas, Adobe Flash or Adobe Premiere: a time-line for time-based media, drag and drop of resources on a paged book and a traditional menu bar.

Usable right out of the box, Sophie comes from a highly experienced and dedicated team, but don’t expect this version to be free of bugs. The release will give you a good idea of the product and of what’s to come. The Mac and Windows version is a bit farther along than the Linux version, but the team is quickly fixing bugs on the Linux version, too.

I think the team’s real challenge is not technical but business: how does one promote a new multimedia format that will compete against predominant formats such as PDF (Adobe has just released PDF format), Adobe Flash and other eBook formats?

Why don’t you try it out and let’s share some Sophie books. It looks like fun!

Links:
Download Sophie
Sophie tutorials
Institute for the Future of the Book

David Battino

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Location, location, location: In this brief online video, podcaster David Adam Weiss demonstrates how to improve your voiceovers dramatically just by tweaking your mic position.

Weiss Mic Position

Weiss makes his point with a $65 Giant Squid mic taped to a ballpoint pen, but says it works equally well with the $15 mic he uses for Boston Behind the Scenes.

After watching the Weiss demo, I looked more closely at the technique Australian broadcaster Ken Sparks used with the Rode Podcaster mic. Notice how he too avoids P-pops by talking past the mic rather than right into it:

Podcaster Mic Technique

Sometimes it’s the little things that make the biggest difference.

David Battino

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Annoyed by the handling noise my pocket voice recorder picks up, I bought some external mics last fall. Not only did the noise disappear, the recordings also gained much more bass and stereo depth.

The mics I got were Sound Professionals SP-TFB-2s, which someone recommended in this field-recording forum. Interestingly, the TFB-2s are designed to fit in your ears, using the shape of your outer ears and head to create a binaural image. When I wear them, people just assume I’m wearing ear buds, which is great for covert recording.

SP-TFB-2 Ears

The TFB-2 mics, with and without optional windscreen. Installing them in your ears takes some practice and a mirror at first.

The mics use an omnidirectional pattern, which produces a very spacious sound, but picks up lots of reverberation indoors. You can hear the effect in this recording of metronomes at the NAMM musical instrument show. The first part of the recording uses the voice recorder’s built-in mics. Then I switch to the in-ear mics.

Here’s another before-and-after example—a bagpipe troupe from the opening day at NAMM. You can hear the drums overwhelm the voice recorder’s automatic gain control, but the difference in frequency response and imaging is obvious.

I put some more TFB-2 examples in the Digital Media Insider podcast about portable recorders, including one recording I made outdoors, where I think these mics work best.

SP-TFB-2 beige

I got the beige color; the mics are also available in black.

What happy recording discoveries have you made?

David Battino

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iTunes podcast URL

Digital Media Insider

I recently listed my podcast at the iTunes Store and wanted a shorter way to give out the URL. The standard link you get by right-clicking the tile is this monstrosity:

Note that the important part is the last nine characters, the iTunes numeric ID. Apple’s Scott Simpson clued me in to this little-known shorter version of the URL:

That’s much better, but still not very memorable. If you register at SnipURL.com, you can make even shorter links. Here’s the one I came up with for the show:

And, of course, if you own your own domain, you could simply set up a page with a meta refresh, name it index.html, and place it in an appropriate subdirectory like myshow. Then your link would be http://www.yoursite.com/myshow. Here’s the tag for the index.html page (substitute your ID for mine):

<META HTTP-EQUIV=REFRESH CONTENT="0; URL=http://www.itunes.com/podcast?id=207870198">

If you have server access, usability experts recommend using an HTTP redirect instead of a refresh.

David Battino

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Kikkoman RedDownloading a photo from a Web page is easy—you just right-click it or drag it to your desktop. But what if you want to grab an embedded movie or sound? Try this simple technique.

Erica Sadun

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Device Certificate after the jump.

Erica Sadun

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Here are the folder and device properties specifically for my Zune, plus its supported filetypes. I’m guessing the Sync partner is the one computer that my Zune hosts to. Biff is the meta-syntactic name I selected as my Zune ID. The Bytes/Free bytes are accurate. The Battery level seems low as it reads as fully charged on the device and has been plugged in for over 24 hours. When I mount the Zune on my PC, the disk name is indeed “Storage”.

The native playback is also interesting. I’ve found that I can sneak around bitrate limitations imposed by the Zune software, but more about that another day.

Special directories:
Default music folder: 0×05000001
Default playlist folder: 0×00000000
Default picture folder: 0×0500001a
Default video folder: 0×0500001e
Default organizer folder: 0×00000000
Default zencast folder: 0×00000000
MTP-specific device properties:
Friendly name: Biff
Synchronization partner: {303B6311-C247-4E9E-B9E6-E9B7AE437BC7}
Total bytes on device: 29806592000 (28425 MB)
Free bytes on device: 28740386816 (27408 MB)
Storage description: “Storage”
Volume label: “14badbab - 0aee704e - 80bd1ff8 - 8ee00652″
Battery level 93 of 100 (93%)
libmtp supported (playable) filetypes:
ISO MPEG Audio Layer 3
Microsoft Windows Media Audio
Microsoft Advanced Systems Format
Microsoft Windows Media Video
JPEG file

Erica Sadun

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This one is really long, so I’ve hidden most of it behind the jump. Here are the Playable File/Object Types and the object properties supported for each one.

Erica Sadun

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Supported operations:
1001: Get device info
1002: Open session
1003: Close session
1004: Get storage IDs
1005: Get storage info
1006: Get number of objects
1007: Get object handles
1008: Get object info
1009: Get object
100b: Delete object
100c: Send object info
100d: Send object
100f: Format storage
1010: Reset device
1014: Get device property description
1015: Get device property value
1016: Set device property value
1019: Move object
101b: Get partial object
9810: Get object references
9811: Set object references
9802: Get object property description
9807: Get interdependent property description
9801: Get object properties supported
9803: Get object property value
9804: Set object property value
9805: Get object property list
9806: Set object property list
9808: Send object property list
9101: Get secure time challenge
9102: Get secure time response
9103: Set license response
9104: Get sync list
9105: Send meter challenge query
9106: Get meter challenge
9107: Set meter response
9108: Clean data store
9109: Get license state
910a: Unknown(910a)
910b: Unknown(910b)
9201: Unknown(9201)
9202: Unknown(9202)
9204: Unknown(9204)
9212: Unknown(9212)
9213: Unknown(9213)
9214: Unknown(9214)
9215: Unknown(9215)
9216: Unknown(9216)
9170: Unknown(9170)
9171: Unknown(9171)
9172: Unknown(9172)
9173: Unknown(9173)
9180: Unknown(9180)
9181: Unknown(9181)
9182: Unknown(9182)
9183: Unknown(9183)
9184: Unknown(9184)
9185: Unknown(9185)
Events supported:
None.
Device Properties Supported:
0xd181: Unknown property
0xd101: Secure Time
0xd401: Synchronization Partner
0×5001: Battery Level
0xd102: Device Certificate
0xd402: Device Friendly Name
0×5002: Functional Mode
0xd405: Device Icon
0xd103: Unknown property
0xd211: Unknown property
0xd131: Unknown property
0xd132: Unknown property
0xd215: Unknown property
0xd216: Unknown property

Erica Sadun

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USB low-level info:
bcdUSB: 512
bDeviceClass: 255
bDeviceSubClass: 0
bDeviceProtocol: 0
idVendor: 045e
idProduct: 0710
IN endpoint maxpacket: 512 bytes
OUT endpoint maxpacket: 512 bytes
Device flags: 0×00000000
Device info:
Manufacturer: Microsoft
Model: Zune
Device version: 01.01.00322.00-00309
Serial number: 14badbab - 0aee704e - 80bd1ff8 - 8ee00652
Vendor extension ID: 0×00000006
Vendor extension description: microsoft.com: 1.0; microsoft.com/WMDRMPD: 10.1; microsoft.com/WMPPD: 11.1; microsoft.com/WMPMCPREMCONT: 1.0; microsoft.com/AAVT: 1.0; microsoft.com/WMDRMND: 1.0; microsoft.com/MTPZ: 1.0;

David Battino

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Audioforce tutorials Audioforce.net is a directory of free online audio-production tutorials. The external links call up everything from single-sentence tips to digitized magazine articles to movies.

To view previous entries, please refer to the Archives menu in the right column.