Poor-quality audio encoders built into CCTV cameras mean that end users could be missing out on the potential to capture vital evidential information.
Click here to view Figure 1.
According to Paul Murphy, marketing manager at IndigoVision, audio hasn’t been seen as a priority in surveillance, and although many of the latest IP cameras boast of high-definition image capture, they fall short of the mark when it comes to the quality of their audio offering. He told IFSEC Global:
Audio is often seen as a niche application in security, with most cameras using poor audio encoders. If the right audio codec is used — it can be a huge compliment to video evidence.
Like video, audio needs to be compressed in order to make it easier to store and transmit over network and there are a number of codecs that will compress audio. Most cameras on the market with an in-built audio feature use the G.711 and G.728 compression codecs. These were built originally for the telecommunications industry to transport the human voice over long distances. G.711 was first released in 1971 and G.728 in 1992 — so they have been around awhile.
Murphy continued:
Because these codecs were built around the human voice, they remove all other noise that isn’t in the human voice range. You can hear how a G.711 or G.728 codec affects noises outside the human vocal range when you are placed on hold and have the pleasure of hearing music that is played to you to keep you on the line! You don’t get any bass or high notes.
IndigoVision’s new Enhanced Standard Definition (SD) range (including the 9000 Series) of cameras now all come with a built-in audio features based on the AAC codec, which was developed in the late 90s for digital audio and is the standard format for most music players.
IndigoVision says that it has seen a number of its customers, particularly in the Latin American region, use the IndigoVision solution to provide “help points” around the city to enable people to alert central monitoring to a problem.
Of course, the use of audio in addition to images treads a fine line between security and a breach of privacy. The Information Commissioner’s Office (ICO) Code of Practice suggests on its website that an audio function should be used in a limited range of applications — for example, as an alarm or alert to certain sounds such as breaking glass, or at a help point or as trigger to begin recording in response to a specific threat.
End users have the option of having the mic built-in or connecting to an external mic. Mark Staples at UTC Fire & Security said:
Audio will probably always be better with an external device. But in terms of quality it has certainly come on and is better now than it was five years ago.
UTC’s UltraView 650TVL WDR box camera offers an in-built solution and also provides 650TVL high resolution and 0.01 lux sensitivity.
Trevor Wallace, managing director of UK security systems installer, Metro Security told us that while audio as a built-in feature of a surveillance cameras is a more discreet option — the sound you get will often be compromised:
In nine times out of ten we prefer to use separate, more advanced conferencing microphones to ensure, for instance, that the conversations by staff in a retail shop which we want to hear are not compromised by other background noises and this is best achieved using higher quality bespoke audio equipment. Built-in mics are certainly improving, but as part of a camera that’s designed to capture images, rather than audio, they still have their limitations.
Of course the type of solution you opt for will depend on the application and high quality in-built audio comes at a price. For Murphy this is well worth paying:
The benefits far outweigh the negatives of high-priced cameras. With AAC you can pick up background noises such as breaking glass, footsteps or gun shots. Having audio clarity helps gives greater evidence for audio applications in security.
What’s your audio solution for video surveillance? Is it something you even need?
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Claire, thanks for this, interesting area of surveillance that we don’t talk about very often. I wonder, how does adding in audio affect storage considerations?
Great article Claire, audio certainly needs to be considered for CCTV systems. I have designed in audio into several security solutions, mainly external CCTV systems and always via separate loudspeakers with shrouded microphones to enable bi-directional audio. It would be great if this could be achieved in one camera unit but I’ve not come across one in my research, unless you know different of course! Control Room operators being able to speak with people on site to either educate following false alarms or verify legitimate access makes the system more user-friendly, adds value and makes the solution much more effective.… Read more »
interesting, I did see new technology where option to compress audio on the go, do not take much space on the hard drive…
but in Canada a lot of the times courts do not accept audio recording…
Really? Why not? Do they accept video surveillance with no quibbles? Why would audio be any different? (I know you’re not a judge so fair enough if you’re not sure!)
in Canada by law you must notify suspect before recording for evidence to be admissible in court…
Interesting point, wonder what the Law says in the UK? We have to “advise” people via signs that they are being recorded by CCTV, not sure about audio but I’ve only ever used it as a live bi-directional feed.
The UK CCTV Code of Practice seems to indicate that we are probably the same as Canada on this one! Extract below; CCTV must not be used to record conversations between members of the public as this is highly intrusive and unlikely to be justified. You should choose a system without this facility if possible.If your system comes equipped with a sound recording facility then you should turn this off or disable it in some other way.There are limited circumstances in which audio recording may be justified, subject to sufficient safeguards. These could include: – Audio based alert systems (such… Read more »
Once you determine that you do want (high quality) audio with your video, what are the popular over IP standards for audio traveling with the video ?
It is also possible to analyse audio to trigger audio recordings/alerts based on specific events such as glass break, car alarms, gunshots and aggression. For example Next Level Security Systems have audio analytics on their gateway products. http://www.nlss.com
The only one I’ve heard of is Real-time Transport Protocol (RTP), not really my area of expertise but would suggest getting a manufacturer to demonstrate its application and quality end-to-end is probably the best way forward.
You can also use audio analytics to detect specific sounds such as glass break, gunshots, car alarms and aggression to trigger recordings or other alerts. For example Next Level Security Systems (http://www.nlss.com) does an appliance that does this using IP cameras with built in or external microphones. There is also a UK company that supplies software that does this http://www.audioanalytic.com.
The Principal of an educational establishment (customer) with digital IP cameras benefited from audio four years ago and wrote:
The ‘live’ audio with colour video is a big plus – it facilitated resolution of a few incidents with conflicting versions, illustrating ‘justice is being done’. The students welcome the surveillance system, because it helped eliminate bullying and disruptive behaviour.
Hence, in my opinion:
‘Audio is very significant in Video surveillance™’.
It’s the beginning of a new phase in digital surveillance evolution.
Thanks for digging this out Tony. Sounds about right. There were a whole load of stories last year on taxis that I worked on including the following:Southampton Council ordered to erase CCTV audio recordingsTaxi CCTV debate rumbles on
So the ICO are clearly looking at how audio is used in surveillance. The problem with some of these cases, I seem to remember, was the ‘always on’ nature of the audio recordings. This seems to marry with that last bullet point you highlighted.
What’s with the trademark symbol @roy sinha-roy? I think it’s certainly interesting, but only when it’s controlled and valid. Audio detection of breaking glass is one thing. Audio recordings of any conversation is another. That data needs to be very strictly controlled. Any opportunity for an abuse of that data use could have significant consequences.
I agree that audio is significant when it comes to video surveillance. It adds context to what you’re seeing. It even adds to what you aren’t really seeing, ie. the sound of a gunshot or glass breaking from a distance, even though what’s causing it isn’t captured in the video. There’s value in audio, there’s no doubt about that.
I didn’t consider how legislation could affect the admissibility of what has been recorded during surveillance. Does this also apply for video recording or is it limited to just audio?
Rob,
We believe ‘audio is key in video surveillance™’
and hence our interest in registration of the trade mark.
We also believe, you will see a lot of activity in this arena, which will take digital video surveillance to a new level.
Regards,
how I see it this days criminals do have more rights and protection…under Canadian law… it sad but in Canada it grim reality…
The UK CCTV Code of Practice mainly covers CCTV installations and mentions the audio bit in relation to it being integrated with CCTV, well worth a read!
http://www.ico.org.uk/upload/documents/cctv_code_of_practice_html/index.html
Sorry, but who is we? Your company?