Using an IP Camera with Audio
Two-way audio is available through an IP Camera

IP cameras are getting more and more sophisticated.  Many of the newer cameras include two-way audio, but what do you need to know to make the best use of audio capability?  This article answers the questions: What are the best cameras, microphones and speakers for the applications? How good is the audio and how do you use it?  How do you talk to many people or just one person?  How do you record the audio and what are the legal implications?  Here are the answers to all your questions.

Overview of Applications
Audio is great for certain applications. An IP camera system can be used in a visual intercom application. For example, the camera can be placed at a doorway and with an attached microphone and speaker allows you to communicate with a person somewhere else in the building (or even over the Internet).  You can even use the output IO from the camera to control a relay that unlocks a door.

IP cameras with audio have been used in interview or interrogation rooms. It provides a simple way to keep a record of what is seen and heard. In this case special software is required to store the audio with the video. 
Some people have even used an IP camera system to store and distribute presentations on the Internet. 
Be aware that there are certain state and federal laws that relate to recording audio (wire tapping), and in most cases require people to be notified they are being recorded.

Cameras with Audio
In almost all cases a camera that includes audio, supports MPEG4 compression.  This form of compression includes data packets for audio transfer as well as video.   picture3For example, the Axis 210A includes two-way audio.  It has audio input and audio output so you can attach a microphone and powered speaker.  Other cameras with audio include Axis214PTZ and Axis211A, Vivotek IP6112, Panasonic WV-NS202 and WV-NP244.
Here are more details about the Axis210A which includes support for two-way audio.

The AXIS 210A, indoor only camera with Computar 2.8-12mm manual focus, manual iris lens, delivers Motion JPEG images at up to 30 frames per second in all resolutions up to 640x480. With a built-in microphone and the ability to connect to external speaker or microphone, the AXIS 210A enables remote users to not only view, but also listen in on an area and communicate orders or requests to visitors or intruders.  Includes built-in motion detection, and provides both full frame rate Motion JPEG and MPEG-4 video streams simultaneously.  MPEG-4 compression mode is ideal for applications where available bandwidth is restricted and higher frame rates are required. Built-in Power over Ethernet allows the camera to receive both data and power over a single Ethernet cable.

Just like any application using audio, you have to consider how to pick up the sound. If you just use the microphone on the camera (some cameras have this included) you will pick up all the audio in the room, including noise you don’t want.  The microphone should be as close as possible to the person.

You can use many different kinds of microphones including handheld, wireless microphones and even directional room microphones. Just make sure the type of microphone matches input requirements of the camera.  Most of the cameras take “line level” type mics.  These line level microphones are similar to those used with audio components such as CD and DVD players, TVs, audio amplifiers and other consumer equipment.  Cameras usually accept the 3.5mm mono audio input connector. In some cases the microphone doesn’t have the right connector for the camera, but this can be corrected by using an adapter. 
General Microphone
picture4If you just want to be able to hear a person at another location, you can use a standard microphone.  Just make sure the microphone cable has the right connector (usually mini-plug). To connect to the camera audio input. For example:

The Paso Professional hypercardioid mic is great for recording, studio, stage, vocal and PA. This is a rugged die-cast construction microphone with 50 – 18,000 Hz frequency response. Dual anti-pop windscreen and includes 15 ft. detachable cable with 3 pin XLR audio male connector at equipment end and carrying case.

Since this microphone has an XLR connector, you need to add a XLR plug to mini plug audio cable so it can be plugged into the camera.
Room Microphone for interrogation
Yes, we did say that a room microphone is not usually recommended, especially for large meeting rooms, but it will work in small interview or interrogation rooms. The Louroe omni-directional microphone can be used in this application.  This uses a very sensitive electret condenser omni-directional microphone. Since this type of microphone doesn’t provide the right electronic output signal, the package includes a pre-amp so it can be used with the camera.  The police like this for interrogation rooms. 
The following kit includes everything you need to pick up sound in a room.

ASK-4 Kit300
picture5Single zone audio monitoring system designed for direct connection to a camera. Omni-directional microphone can pick up normal sounds 15’ away or within a 30’ diameter circle. Package includes the 3.5mm mono audio output required for a camera. A connector cable is also included. Distance between the Verifact A. Microphone and Model IF-1 Interface Adapter may be up to 1,000 ft. using recommended wiring.

There are many other microphones that can be used.  Contact me for some more recommendations.
You can talk through an IP camera that has audio output.  Some cameras have built-in speakers, but in most cases you need an external powered speaker.  The speaker needs to be powered because the camera doesn’t have enough amplification power.  The cameras that support two-way audio have a 3.5mm mono audio output similar to the microphone input connection. I have seen some cameras with only one shared audio connection so be careful about this.  In this case you need to use a splitter that allows both a microphone and speaker to be connected.


Almost any type of powered amplification system, like a PA system, can be connected.  There are also some special powered speakers available that can be connected directly to the cameras.  Here’s one example:

Speaker assembly for the cameras.  The IPX-SA which is a 5” square, weather-resistant, black, metal, speaker box (2” depth) with a built-in amplifier.  This unit can be wall-mounted outdoors but it is not designed to withstand direct moisture or harsh environments.  The amp takes a 12VDC input which can be pulled from the 12VDC terminal inside the IPX-ED-24V enclosure
The price is $135

How to speak through the camera
At the moment, you can only speak through a PC (with sound card and microphone) using Internet Explorer.  There is a microphone button that can be pushed to allow you to send audio through the network to the camera with the speaker. Software companies are working on support for out bound audio.
Doorway Intercoms
picuture7To have a two-way conversation with someone at a doorway requires both a microphone and speaker. The microphone and the speaker must be compatible with the input and output requirements of the camera.  It’s best to use a directional microphone to minimize any extra noise in the area.  Here’s an example of a two way system that is compatible with most cameras.

Bi-directional Speakerphone.  Surface Wall mount speakerphones are designed to interface with various modes of audio/video transmission systems. They provide bi-directional audio with the IP Network cameras that support audio, and video servers with audio support. It contains a built-in electret condenser microphone and a 4" speaker. Also control potentiometers for adjusting the sensitivity of both transmitted and received audio.  It can be used outdoors but requires protection from direct exposure to the elements.

How to hear the sound at a PC
A PC with a sound card and speakers allows you to view the video and hear the audio.  You need special software if you want to store the audio along with the video. Broadcasting the video and audio to many people requires different software.
Viewing and hearing the audio
The simplest way to view an IP camera and listen to the audio is to use a web browser.  Internet Explorer accepts the ActiveX component provided by the camera that allows you to see and hear the camera. Unfortunately many of the other browsers don't support the Active X. Also only a few people (depending on the camera up to 10 or 20 people at a time) can view the video at the same time.
Storing the Audio with the Video
To store the video and audio you need special IP software.  OnSSI has a number of surveillance software products that records audio as well as the video. For example, ProSightSMB software records video from up to 25 cameras, but only allows you to record the audio from one camera. NetDVR software supports up to 64 cameras and allows you to record audio from all these cameras. NetDVMS supports hundreds of cameras and records audio and video. It also allows you to hear the audio at both the server and at various PCs on the network that are running NetGuard-EVS client software. 
Here’s an example of the software that can be used:

4 Camera license - NetDVR provides access, viewing and control of surveillance cameras from any location on the network. Totally software based system which can be installed on a standard PC workstation. Software allows you to do an instant Search on time date or activity alarm. It supports up to 30fps per camera, and even records audio. Secure time stamped and watermarked recordings. Fully adjustable Video Motion Detection. The license can be expanded by trading in the software for the next level of license.
The list price is $1,295 contact us for your price.

If you need more information please contact us.  We can be reached at 914-944-3425 or by contact form.


Published by Bob Mesnik
Copyright © 2007 Kintronics, Inc.. All rights reserved.
For more information, please contact us 1-800-431-1658 or 914-944-3425 (outside the USA) or by email infohome at kintronics.com
Powered by IMN