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doc:appunti:linux:audio:audio_recording [2019/04/23 12:50] – [Web References] niccolodoc:appunti:linux:audio:audio_recording [2019/05/22 15:51] – [Electrical compatibility and hardware autodetection] niccolo
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 As stated above, the first problem is **powering the microphone** itself, because generally we will use an **electret** one. It is a **common practice** to provide the power on the same line of the microphone signal, so **requiring just two wires** for both power (from the device to the mic) and for signal (from the mic to the device). The power, also called //bias current//, is generally in the range of **2.5** to **5.0 volt**. As stated above, the first problem is **powering the microphone** itself, because generally we will use an **electret** one. It is a **common practice** to provide the power on the same line of the microphone signal, so **requiring just two wires** for both power (from the device to the mic) and for signal (from the mic to the device). The power, also called //bias current//, is generally in the range of **2.5** to **5.0 volt**.
  
-FIXME: How much current is provided in our test? Is the current always present or switched-on only at jack insertion?+On a Xiaomi Mi A1 smartphone, which has a **TRRS 3.5 mm jack, CTIA standard**, we measured a bias current of **2.19 volt** between the microphone (sleeve) and the ground (ring).
  
 Another parameter which should be considered is the **impedence** FIXME Another parameter which should be considered is the **impedence** FIXME
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   * [[https://stackoverflow.com/questions/47394634/difference-between-voice-communication-and-mic-in-mediarecorder-audiosource|Difference between VOICE_COMMUNICATION and MIC in MediaRecorder.AudioSource]]   * [[https://stackoverflow.com/questions/47394634/difference-between-voice-communication-and-mic-in-mediarecorder-audiosource|Difference between VOICE_COMMUNICATION and MIC in MediaRecorder.AudioSource]]
   * [[https://stackoverflow.com/questions/47359587/what-is-the-best-audiosource-setting-for-calls|What is the best audiosource setting for calls?]]   * [[https://stackoverflow.com/questions/47359587/what-is-the-best-audiosource-setting-for-calls|What is the best audiosource setting for calls?]]
 +  * [[https://amp.reddit.com/r/androidapps/comments/4wo8sz/app_to_force_android_to_use_external_microphone/|App to force android to use external microphone when one is plugged in]]
doc/appunti/linux/audio/audio_recording.txt · Last modified: 2020/12/28 18:22 by niccolo