November 14, 2012

Video and Audio Recording with RCA Connectors: Primer for Surgeons

In the medical world, video recording of surgical procedures is not unusual, especially when it comes to endoscopy.

A camera attached to an endoscope throws up a live image to a screen for the surgeon (and others) to watch. Video output for recording is now standard in such situations.

The monitor where the endoscopy procedure is viewed itself contains video output plugs.

The endoscopy equipment itself like the KayPentax EPK-1000 contains not just one video output, but 3... Two S-video and one RGB.

As such, one could hook up literally any type of recording device and get a beautiful video copied into any type of media very easily whether laptop computer, VHS, CD, thumb drive, etc.

HOWEVER, audio recording simultaneously with endoscopy is not typically a built-in feature and as such requires some MacGyver action.

Why in the world would a surgeon want to record audio? Well, take ENT surgeons who perform vocal cord procedures where the voice is the main outcome measure. It would be great to be able to record not just the video, but the audio of the patient's voice as the procedure is performed.

So what to do?

The simplest way to record audio and video is to take a camcorder and record the screen. The camcorder will be able to record the video (via shooting the monitor) and has built in microphone to record the surrounding audio. One can also attach a lapel microphone and plug it into the audio jack of the camcorder if available.

The downside with this simple method is the video quality. You are after all recording a screen rather than getting the pure digital video signal which would provide the best video picture.

Well, the surgeon will need to obtain a digital AV converter box which has the ability to merge separate video and audio signals and merge it into a single AV signal that is then fed into a computer to record. With this setup, the computer is tricked into thinking the video and audio as coming from a single source like a camcorder.

The problem is that all AV converter boxes (as of Nov 2011) utilizes RCA audio ports (red and white).

One can not simply buy a microphone with appropriate RCA adapters and plug it into the AV converter box. IT WILL NOT WORK!

Why? Because RCA connectors contain no power. Typically, RCA connectors go from something that already has a power source like a DVD player, camcorder, or TV. The current crop of digital AV converter boxes assumes that the user is trying to copy a movie or show onto a computer.

But for the surgeon, that's not what is occurring.

We literally just want to connect a microphone (which inherently has no power supply) to the RCA audio ports on the AV converter box.

In order to do this, a power supply needs to be provided to the microphone BEFORE plugging it into the RCA ports.

What is this power supply unit? It's called a microphone pre-amp.

So the connections go something like this:

microphone on patient --> microphone pre-amp --> AV converter box --> computer to record

A variety of plug converters will be required in order to plug each component to each other.

For those who want to duplicate what I've specifically done, here are the components (Amazon links provided below):

1) Microphone - Audio-Technica Pro 8HEx Microphone
2) Microphone Pre-Amp - ART Tube MP Studio Mic Preamp
3) AV Converter Box - Canopus ADVC110 Converter

Fauquier blog
Fauquier ENT

Dr. Christopher Chang is a private practice otolaryngology, head & neck surgeon specializing in the treatment of problems related to the ear, nose, and throat. Located in Warrenton, VA about 45 minutes west of Washington DC, he also provides inhalant allergy testing/treatment, hearing tests, and dispenses hearing aids.

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