How to Record Great Audio in iOS and Android Video Production

As cameras on smartphones and tablets keep improving, it increasingly reveals audio as the weak link in mobile-produced videos. Actually, to be fair, audio is the weak link in any video when you use the camera's internal microphone to record audio. That's why virtually all video producers use external microphones when shooting with their camcorders or DSLs. In this article we'll describe how you can do the same with your iOS-produced videos. Next month, we'll provide some mini-reviews of products customized for mobile audio capture.

iOS and Android Audio Compared

Apple's and Google's obvious goal for their video recording apps was to make them as easy to use as possible. In this regard, neither allows you to change microphones within their respective video recording program. However, when you plug a new microphone into an iPhone (and presumably other iOS devices) it automatically becomes the default microphone. That holds true whether you use the headphone jack or the lighting connector. You'll want to record a quick clip to be sure, but that's how it worked in all our tests.

With the Nexus tablet we tested, however, Android made microphones plugged into the headphone jack the default mic, but only for audio recording apps. In our tests, the video recorder always defaulted to the internal microphone. Interestingly, when we plugged a USB mic into the USB port, we had to use a special software program called USB Audio Recorder Pro to recognize it. None of the other audio recorders we had installed would recognize it. And again, the Android Video Recording app never changed from the internal mic.

An Android video recording app named IgCamera App promises to let you change microphones within the program's interface, but we never got satisfactory results in testing. While it seemed to recognize mics plugged into the headphone jack, it crashed repeatedly.

We tested in March 2015, and things change. If you have an Android mobile device and want to try recording with an external mic, check to see if the video recorder lets you switch mics, or if it switches automatically when you install a new mic.

Most of the next section applies equally to iOS and Android devices.

Start With the Jack

All mobile devices include a 3.5mm headphone jack, and most of these include a microphone input. If you've ever tried to simply plug a 3.5mm microphone into this plug, however, you know that it doesn't work. That's because the connectors don't match up, as you can see in Figure 1. Fortunately, there's a simple solution.

On the left is the connector for Apple EarPods that come with an iPhone 6. Three lines break the connector into four separate channels: one carrying left and right audio from the phone to the headphones, one carrying mono audio from the microphone to the phone, and one serving as the ground. This is called a TRRS connector, for Tip, Ring, Ring, and Sleeve.

On the right is a stereo connector from a standard 3.5mm microphone. Two lines divide the connector into three channels, two for audio in, one for ground. (Since virtually all of these devices have a single microphone the audio signal isn't stereo, but let's not quibble: We're happy the listener has sound in both ears.)

Looking at Figure 1, you can see that the channels don't match up, which is why the mic on the right won't work when plugged into a mobile device's TRRS jack. The solution is to use an adapter like the Azden i-Coustics HX-Mi TRRS Mic/Headphone Adapter shown in Figure 2, which costs $20 on Amazon. It has a TRRS connector on the left, with separate TRS (Tip, Ring, Sleeve) plugs for the headset and microphone.

Most inexpensive mics with 3.5mm TRS connectors use electret sensing devices that require low levels of power from mic input plugs. This is called plug-in power. EarBuds, for example, get that power from an iPhone. Not all adapters carry plug-in power from the plug to the microphone, although the Azden adapter does. Before buying an adapter, check to make sure that it carries plug-in power to the microphone.

Through about 2012, there were two competing (and incompatible) TRRS standards: the CTIA spec used by Apple, and the OMTP spec used by other manufacturers, including Android tablet and phone manufacturers. In 2012, most Android vendors saw the light and switched over, so most Android phones and tablets manufactured after that year use the CTIA spec, as well. That said, the sheer number of Android devices out there makes it impossible to say if a CTIA adapter will work with one device in particular, especially if manufactured before 2012.

Until around 2010, when DSLR video production started becoming mainstream, most high-end mics used XLR connectors. To ride the DSRL wave, however, several vendors started producing high quality mics with 3.5mm connectors. Azden offers several DSLR-focused products that, with the use of an adapter, can be used for mobile video production. Check back next month for a review of two of those mics, both contained in Azden's WHD-PRO+i Shotgun/Lapel system (Figure 3).

If you're buying a new mic for a phone or tablet, search for a TRRS mic. You'll find plenty that connect directly to an iOS and Android device and don't need an adapter.

What About XLR Gear?

Many video producers prefer microphones that terminate in XLR connectors, which, in many instances, require 48 volts of phantom power to operate. No sweat, there are multiple XLR to TRRS adapters, including the IK Multimedia iRig PRE shown in Figure 4 (about $33 on Amazon). It runs for 10 hours on a 9-volt battery. We tested the iRig PRE with several XLR-based mics, including the Shure SM93 lavalier mic and a couple of headset and studio mics, and it worked as advertised.

Going Beyond the Plug

Multiple manufacturers now offer microphones that connect directly to the lightning port on more recent iPads, iPhones, and iPods, including two HK Multimedia units we'll review next month, the iRIG Mic HD and iRIG Mic Field (Figure 5). The benefit of using the lightning connector is that it supplies more power than the headphone jack, and it leaves the headphone jack open for listening during playback. In our tests, the recorder switched to the new mic automatically, so you should have no problem getting the video recording app to recognize either.

You can connect a mic to the USB port on many recent Android devices and record audio with some apps. However, we couldn't figure out a way to use the mic in the video recording app that we tried. So while the thought of recording video with high-quality USB mics is alluring, at this point, we couldn't figure out how to make it work.

Read part two for our mobile audio mic reviews.

Jan Ozer's article first appeared on OnlineVideo.net