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I wonder whether there is a way to reconfigure audio jacks into microphone jacks on an average sound card these days. Little known fact: speakers and headphones

I wonder whether there is a way to reconfigure audio jacks into microphone jacks on an average sound card these days. Little known fact: speakers and headphones are also microphones simply by the physics of how they work.

stagas 8y ago
It happens occasionally that a DJ will plug their headphones to the mic input in their console and talk to the earpiece to make some announcement in bars/clubs when there is no mic available around. But, yeah, if one could turn the headphone output to a mic input using software, that would be major because lots of people leave their headphones plugged.
- lucb1e 8y ago
  The quality is not that good though. I've tried it and I need to speak directly into it, a few decimetres away or a little to the side and it's beyond recognition already. At least with the two or so earphones/headphones (don't remember) that I tried, maybe it's different with other hardware?
  - stagas 8y ago
    But the information is captured, even if the signal to noise ratio is very low. There are audio restoration tools nowadays that work amazingly well, some even using AI(or claiming to) - so even if you have a recording where it sounds just like plain noise, there is still some capacity of extracting the signal you need out of it. That's mostly because the background noise is not random, it is of a certain pattern, constant and repeating and therefore can be captured and cancelled. Then the actual signal we need, which differs from the noise pattern, stands out.
AnssiH 8y ago
hdajackretask on Linux does that, part of alsa-tools. Blog post by author from 2011: http://voices.canonical.com/david.henningsson/2011/11/29/turn-your-mic-jack-into-a-headphone-jack/ http://voices.canonical.com/david.henningsson/2011/11/29/tur... I believe similar utilities exist on Windows at least with some cards.
ngneer 8y ago
I know people who did that via custom driver, it depends on sound card capabilities.
jloughry 8y ago
Yes: Interestingly, the audio chipsets in modern motherboards and sound cards include an option to change the function of an audio port at the software level, a type of audio port programming sometimes referred to as ’jack retasking’. This option is available on most audio chipsets (e.g., Realtek’s audio chipsets) integrated into PC motherboards today. Jack retasking, although documented in the technical specifications, is not well-known [34]. For an in-depth technical discussion on malicious retasking of an audio jack, from the hardware to the operating system level, we refer the interested reader to the following previous work [29]. References: Mordechai Guri and Yosef Solwicz and Andrey Daidakulov and Yuval Elovici. 'MOSQUITO: Covert Ultrasonic Transmissions between Two Air-Gapped Computers using Speaker-to-Speaker Communication'. arXiv preprint 1803.03422v1 [cs.CR], 9th March 2018. Mordechai Guri and Yosef Solewicz and Andrey Daidakulov and Yuval Elovici. 'Speake(a)r: Turn speakers to microphones for fun and profit'. 11th USENIX Workshop on Offensive Technologies (WOOT 17). USENIX Association, 2017.
- ocdtrekkie 8y ago
  Curious how the average user could try to mitigate this threat. Perhaps if you were using speakers connected to an HDMI monitor, rather than an audio jack? Presumably then you'd have to figure out how to exploit both the audio chip on the motherboard and the HDMI device, which I presume would not by default be willing to operate as an input device.

stagas 8y ago

It happens occasionally that a DJ will plug their headphones to the mic input in their console and talk to the earpiece to make some announcement in bars/clubs when there is no mic available around. But, yeah, if one could turn the headphone output to a mic input using software, that would be major because lots of people leave their headphones plugged.

lucb1e 8y ago
The quality is not that good though. I've tried it and I need to speak directly into it, a few decimetres away or a little to the side and it's beyond recognition already. At least with the two or so earphones/headphones (don't remember) that I tried, maybe it's different with other hardware?
- stagas 8y ago
  But the information is captured, even if the signal to noise ratio is very low. There are audio restoration tools nowadays that work amazingly well, some even using AI(or claiming to) - so even if you have a recording where it sounds just like plain noise, there is still some capacity of extracting the signal you need out of it. That's mostly because the background noise is not random, it is of a certain pattern, constant and repeating and therefore can be captured and cancelled. Then the actual signal we need, which differs from the noise pattern, stands out.

AnssiH 8y ago

hdajackretask on Linux does that, part of alsa-tools. Blog post by author from 2011: http://voices.canonical.com/david.henningsson/2011/11/29/turn-your-mic-jack-into-a-headphone-jack/ http://voices.canonical.com/david.henningsson/2011/11/29/tur... I believe similar utilities exist on Windows at least with some cards.

ngneer 8y ago

I know people who did that via custom driver, it depends on sound card capabilities.

jloughry 8y ago

Yes: Interestingly, the audio chipsets in modern motherboards and sound cards include an option to change the function of an audio port at the software level, a type of audio port programming sometimes referred to as ’jack retasking’. This option is available on most audio chipsets (e.g., Realtek’s audio chipsets) integrated into PC motherboards today. Jack retasking, although documented in the technical specifications, is not well-known [34]. For an in-depth technical discussion on malicious retasking of an audio jack, from the hardware to the operating system level, we refer the interested reader to the following previous work [29]. References: Mordechai Guri and Yosef Solwicz and Andrey Daidakulov and Yuval Elovici. 'MOSQUITO: Covert Ultrasonic Transmissions between Two Air-Gapped Computers using Speaker-to-Speaker Communication'. arXiv preprint 1803.03422v1 [cs.CR], 9th March 2018. Mordechai Guri and Yosef Solewicz and Andrey Daidakulov and Yuval Elovici. 'Speake(a)r: Turn speakers to microphones for fun and profit'. 11th USENIX Workshop on Offensive Technologies (WOOT 17). USENIX Association, 2017.

ocdtrekkie 8y ago
Curious how the average user could try to mitigate this threat. Perhaps if you were using speakers connected to an HDMI monitor, rather than an audio jack? Presumably then you'd have to figure out how to exploit both the audio chip on the motherboard and the HDMI device, which I presume would not by default be willing to operate as an input device.