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--- doc:appunti:linux:audio:audio_recording [2020/12/28 17:08] – [Wireless mic on Ugreen USB audio adapter] niccolo
+++ doc:appunti:linux:audio:audio_recording [2020/12/28 17:21] – [Web References] niccolo
@@ Line 127: / Line 127: @@
 ===== Wireless mic on Ugreen USB audio adapter =====
-The device is detected by the Linux Kernel 4.9.0 in this way:
+See this article about **[[audio_recording_usb_adapter]]**.
-<code>
+====== Web References ======
-usb 2-1.3: new full-speed USB device number 5 using ehci-pci
-usb 2-1.3: New USB device found, idVendor=0d8c, idProduct=0024
-usb 2-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=0
-usb 2-1.3: Product: USB Advanced Audio Device
-usb 2-1.3: Manufacturer: C-Media Electronics Inc.
-input: C-Media Electronics Inc. USB Advanced Audio Device as /devices/pci0000:00/0000:00:1d.0
-    /usb2/2-1/2-1.3/2-1.3:1.3/0003:0D8C:0024.0004/input/input18
-hid-generic 0003:0D8C:0024.0004:
-    input,hidraw2: USB HID v1.11 Device [C-Media Electronics Inc. USB Advanced Audio Device]
-    on usb-0000:00:1d.0-1.3/input3
-</code>
-{{ ugreen-usb-audio.jpg?direct&220|Ugreen USB Audio Adapter}}
-The **microphone socket** is a **3.5 mm TRS type** (three poles), it provides a bias current of **2.6 V** on both the **tip** and the **ring**, so it is advisable, as reported in the device manual, to **NOT use a simple two poles mono jack** (TS type), because it will short-circuit the bias current on the ring with the ground on the sleeve.
-Launching **alsamixer** and hitting F6 you can select the **USB Advanced Audio Device** sound card. Hit F4 to view the only one capture device, i.e. the microphone input line. Press **Space** to enable/disable the **capture** and **Up/Down arrows** to increase/decrease the **gain**.
-It seems that the best setting for audio recording through the mic, is to keep the **capture mic gain to 100**:
-{{usb-advanced-audio-device-alsamixer.png?direct&300|USB Advenced Audio Device in Alsamixer}}
-I use the **PulseAudio** subsystem above the ALSA modules (this is the preferred method in modern GNU/Linux distro). In this case the volume is controlled via the graphics app **pavucontrol** or on the command line using the **pacmd** tool. Here are the commands to start an audio recording using a shell script:
-<code bash>
-#!/bin/sh
-SOURCE='alsa_input.usb-C-Media_Electronics_Inc._USB_Advanced_Audio_Device-00.analog-stereo'
-PORT='analog-input-mic'
-VOLUME=65536
-pacmd set-default-source "$SOURCE"
-pacmd set-source-port "$SOURCE" "$PORT"
-pacmd set-source-volume "$SOURCE" "$VOLUME"
-pacmd set-source-mute "$SOURCE" 0
-parecord --verbose --device="$SOURCE" --channels=1 --fix-rate foobar.wav
-</code>
-**WARNING**: The audio files produced by this USB adapter **do not cover the entire 16-bit range**; the values returned (converted into float dB) extend from **-0.5** to **+0.5**, i.e. exactly **the half of what expected** (-1.0 to +1.0). Above that values, the audio is clipped. You can view this in the pavucontrol monitor: it does not matter how loud you speak into the microphone, the volume meter bar never reaches the full scale. So **it is advisable** eventually to lower the volume (e.g. to **75%** or 50%) to **avoid clipping**, and to proceed with post-processing **software amplification**.
-===== Web References =====
   * [[wp>Microphone]]