doc:appunti:linux:audio:audio_recording
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doc:appunti:linux:audio:audio_recording [2019/04/23 11:05] – [Wireless UHF microphone on Android] niccolo | doc:appunti:linux:audio:audio_recording [2019/05/22 15:51] – [Electrical compatibility and hardware autodetection] niccolo | ||
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Despite all this empirical approach, the **voice registration is quite satisfying**! | Despite all this empirical approach, the **voice registration is quite satisfying**! | ||
- | ===== Audio Recording With Android ===== | + | ====== Audio Recording With Android |
- | Recording audio using an **external microphone** connected to an **Android device** can be a real nightmare. We tried the hard way using a Chinese, no-brand **wireless UHF microphone**! | + | Recording audio using an **external microphone** connected to an **Android device** can be a real nightmare. We tried the hard way using a Chinese, no-brand, **wireless UHF microphone**! |
- | We can group the problems you can fece in three main categories: | + | We can group the problems you can face in three main categories: |
* Physical connection | * Physical connection | ||
- | * Hardware | + | * Electrical compatibility and hardware |
* Software capabilities and settings | * Software capabilities and settings | ||
+ | |||
+ | ===== Physical connection ===== | ||
+ | |||
+ | Most Android devices have a **3.5 mm jack** accepting a **TRRS connector in CTIA standard** and every brand of mobile phones produces **headsets** with their own standard. The vast majority of solutions uses **electret microphones** requiring a **bias current**, but use **some combinations of impedence** to detect the insertion of the microphone and to **handle the headset button** (or buttons). | ||
+ | |||
+ | So, connecting an external microphone, can be as simple as making a cable that connects the **ring** and the **sleve** of the **CTIA connector** to (respectively) the **ground** and the **microphone line** of the microphone. The hard part is to guess, or empirically try, if the microphone **requires a bias current**, if the Android device is provinding such a current and if the microphone produces a sufficient **output level** (actually a voltage in the order of the millivolts) that can be used by the device. | ||
+ | |||
+ | ===== Electrical compatibility and hardware autodetection ===== | ||
+ | |||
+ | 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**. | ||
+ | |||
+ | 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 | ||
+ | |||
+ | ===== Software capabilities and settings ===== | ||
FIXME Complete the article! | FIXME Complete the article! | ||
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doc/appunti/linux/audio/audio_recording.txt · Last modified: 2020/12/28 18:22 by niccolo