The point of the GP was to say that while cameras on computers at least pretend to let you know when they are on, microphones do no such thing.

I was once paid specifically to figure out a way to activate a camera without turning on the light.

However in that case it was for a legitimate purpose.

Out of curiosity - what was that legitimation? Can you tell?

One idea: I can easily imagine research studies getting IRB approval for this. The red light could alter the subject's behavior, and video analysis could be part of the metrics (for measuring attention/distraction or gross estimates of gaze, etc).

Really? Because I can't.

I can't imagine an IRB-approved research study that requires a software solution (developed under an NDA) to a hardware problem that couldn't be solved with a one-inch square of black electrical tape.

For the price of a contracted software developer, you could simply buy a model of laptop (or smart phone), in which the bezel can be pried open without substantial damage, and behind the LED's transparent aperture (but obscuring the LED), you fix a tidbit of black tape or whichever opaque material you may prefer.

Or, better yet, for pretty much every situation that doesn't involve eye-movement tracking, simply install a hidden security camera at an opportunistic vantage point.

An IRB would only care about whether the deception perpetrated on the subject is justifiable. They wouldn't care one iota how the light was disabled--the risk to the subject is the same regardless of whether the light is disabled by hardware or software or not used. For example a BYOD type study might be plausible because in some circumstances subjects may be more comfortable/candid using their own devices. Who knows.

The issues for the IRB would only be the fact that the subjects are not consented to covert surveillance and whether the nature of the information collected presents a risk to the subject if accidentally disclosed.

I wish I could.

It's not just that I am still bound by my NDA, but telling anyone what the application actually did, would result in bad things happening to completely innocent people.

I also have a legitimate reason to snap still photos on a smartphone, without making the shutter sound. On an iPhone, it sounds just like an SLR film camera, and is very loud.

However, it turns out that it is unlawful to do that in such countries as Japan.

Asking how to silence the iphone camera on stackoverflow resulted in 20,000 views of my post, several people saying you can't do that, and several people telling me it's against the law, that it would be a bad idea and so on.

Nevertheless, I have a completely legitimate reason to do so.

I expect Apple would reject it from the App Store. I may do it for Android, as well as for jailbroken iOS devices, but then sell it through the Cydia App Store.

I read someone was able to "remove" the click sound by playing the same click sound phase shifted when taking a photo - so when the OS sound mixer adds the two waveforms together it results in silence. Clever idea - it is the same as noise canceling headphones, except it all happens in software.

As others have mentioned, if you put your iphone in silent mode there is no click sound except in Japan. I'm not sure if a) phones sold in Japan have disabled this feature or b) the phone knows when it is located in Japan and then disables silent mode.

I doubt that would work well in practice. The reason is that timing is extremely important for this to work, if you're even one sample off you'll here a faint sound, and more than a few then it's quite obvious. So if the sound is generated by a separate OS process, you'll never know exactly when the sound is generated and you will not even have control over exactly when your own sound is played back in relation to the other process, think sub ms accuracy.

You can disable the shutter sound in Android by just putting the phone in silent mode.

Hey Thanks!

It's just like Apple to be a corporate nanny.

I've done some Android Platform Development, but not yet any real Android App Development. I'll do that after I ship the iOS App I'm working on.

My iPhone doesn't make a peep in silent mode using either the builtin camera app or Camera+.

I haven't actually tried this for quite a long time. Perhaps Apple added a silent mode so as to compete with Android.

There's a lot of stuff that at one time would only work on jailbroken devices, only for Apple to "add support" for it as a result of some App becoming a huge hit at the Cydia App store.

At first one could not even take still photos programmatically, the user had to use Apple's own App for that. But Snapture - if I remember correctly - was able to do it on jailbroken devices, so Apple added the public API so that Snapture would be sold on the App Store, rather than through Cydia.

  > Perhaps Apple added a silent mode so as to compete with
  > Android.

Every single iPhone I had (and I had 3G, 4, 4S, 5, 5S) was able to take photo without sound if it was switched to silent. Probably differs by the region, i.e. those shipped to Japan make camera sound no matter what, others don't.

Is there a way to silence the shutter sound from code?

It doesn't have to be Objective-C and Cocoa Touch. I'd be completely cool with C and system calls.

I have an Android phone that's not rooted, an Acer. Turning off shutter sound is in the camera settings, it's one of the first things I do with a camera as I prefer natural photos of family to posed ones.

Lol silent mode?

Not in Japan.

You realise that this just makes it more intriguing. Personally, I wonder if that's not a way of saying "actually my justification isn't really valid". I don't mean to be inflammatory, I'm voicing my concern -- it sounds fishy.

The whole thing really does sound like he didn't have any legitimate reasons to be doing that and is just deflecting criticism.