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I have done lot of research on data transmission using mobile headphone jack. I go through one library AudioJackTransfer which provide some mechanism for male to male transfer.

I didn't found any useful things. My goal is to capture image/video using Audio Jack of mobile device in Android.

Daniel Nugent
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Pranav
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  • The "built in analog to digital convertor" is of course the microphone input. So search Stack Overflow / the internet for recording audio on Android. Or study the [MediaRecorder](http://developer.android.com/reference/android/media/MediaRecorder.html) class. Probably it's not possible to get enough bandwidth for any usable real-time video data. And an A/D converter of course supports analog "data" so any analog signal that's at a suitable level and in a suitable frequency band -- probably something like 0 to 20 kHz as it's meant for audio. – Markus Kauppinen May 06 '16 at 08:39
  • yes you are right analog to digital is for micro phone. But i came to know that selfie stick uses some mechanism for send something using Audio Jack that camera application understand and capture image. Right now i am doing R&D on this thing. – Pranav May 06 '16 at 08:44
  • Okay, so you just want to trigger the capture via the audio jack. Some Bluetooth based remote control devices install as a keyboard and send key events to capture, start/stop audio playback and adjust volume. If you are writing your own camera app there's of course no problem, but if you want to control the Android camera app. then you'll need to find a way to send key events (volume up or down to capture). – Markus Kauppinen May 06 '16 at 10:11
  • It might be possible with [UiAutomation](http://developer.android.com/reference/android/app/Instrumentation.html#getUiAutomation()). And then of course you would have to listen to the microphone input to detect the trigger signal. [According to this](http://stackoverflow.com/questions/10477547/background-access-to-microphone-in-android) it should be possible even in the background. – Markus Kauppinen May 06 '16 at 10:11
  • I haven't tried out these things myself so I'm just commenting. – Markus Kauppinen May 06 '16 at 10:12
  • Actually the Android camera app seems to react to the buttons of a regular wired headset but the two devices I tried behaved differently. The other one does not react to volume buttons at all but the middle button captures an image. The other one captured with either of the volume buttons. They are of different brand and running a different Android version. (Lollipop and Marshmallow) – Markus Kauppinen May 06 '16 at 11:52

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