From: (Anonymous)
Given that:
- In smartphones and many device using SOC[1], Many of the CODECs[2] used can indeed configure the functions of pins trough software. This is typically done by the Linux kernel.
- In laptops there are microphones too, and the pins can also be reconfigured. This is often called "retasking" for Intel "sound cards".
- Desktop computers falls into the same categories than laptops but have no microphone

Assuming that the user removed all internal microphones of the given device (smartphone or laptop) or has a desktop computer, how is the above relevant?

If we assume that the CODEC or sound card has no special constraint with routing the pins to the function[3], we then can easily test it.

To do that you can either:
- Connect your headphones to the microphone jack and test how much sound level you can record.
- Try to reroute pins, a retasking GUI exists for intel HDA sound cards and try to record.

The issue is then that the volume of the sound you recorded is not the same with headphones than a microphone because of physical constraints: The microphone is physically designed to get sounds transformed as electricity. If the speaker require a lot of power to operate, then you would need in return to shout very loudly to make the membrane vibrate enough to produce electricity...

The question is then how much usable is the recording. Do algorithm exist to isolate voice in that context? Will they exist tomorrow?

[1] System on a chip, the "Processor" of your phone.
[2] A CODEC is the analog part of the "sound card". It is typically connected to the SOC trough PCM.
[3] You will need to check the relevant datasheets to find out.

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Matthew Garrett

About Matthew

Power management, mobile and firmware developer on Linux. Security developer at Google. Ex-biologist. @mjg59 on Twitter. Content here should not be interpreted as the opinion of my employer.

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