Audio

Audio Interface Introduction

Several audio interfaces on the development board:

  • Audio input interface: headphone, MIC
  • Audio output interface: headphone, speaker, HDMI
AUDIO

Sound card device

Get a recording device

root@linaro-alip:/# arecord -l
**** List of CAPTURE Hardware Devices ****
card 0: rockchipes8388 [rockchip-es8388], device 0: dailink-multicodecs ES8388 HiFi-0 [dailink-multicodecs ES8388 HiFi-0]
  Subdevices: 0/1
  Subdevice #0: subdevice #0
  • card 0：Onboard audio processing chip rockchip-es8388, which leads to two recording interfaces, one for the onboard MIC and the other for the headphone MIC
  • Card 0 is the device registered in Linux. We can call these interfaces through the application

Get playback device

root@linaro-alip:/# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: rockchipes8388 [rockchip-es8388], device 0: dailink-multicodecs ES8388 HiFi-0 [dailink-multicodecs ES8388 HiFi-0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: rockchiphdmi [rockchip,hdmi], device 0: rockchip,hdmi i2s-hifi-0 [rockchip,hdmi i2s-hifi-0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

  • card 0 : onboard audio processing chip rockchip-es8388

  • card 1 : HDMI audio output

Card 0 and card 1 are devices registered in Linux. We can call these interfaces through applications.

Sound card driver directory

View the sound card driver directory

root@linaro-alip:/# ls -l /dev/snd/
total 0
drwxr-xr-x  2 root root       80 Oct 10 17:40 by-path
crw-rw----+ 1 root audio 116,  4 Oct 10 17:40 controlC0
crw-rw----+ 1 root audio 116,  6 Oct 10 17:40 controlC1
crw-rw----+ 1 root audio 116,  3 Oct 10 17:40 pcmC0D0c
crw-rw----+ 1 root audio 116,  2 Oct 10 17:40 pcmC0D0p
crw-rw----+ 1 root audio 116,  5 Oct 10 17:40 pcmC1D0p
crw-rw----+ 1 root audio 116,  1 Oct 10 17:40 seq
crw-rw----+ 1 root audio 116, 33 Oct 10 17:40 timer

  • controlC0：used for sound card control. C0 stands for sound card 0, corresponding to the onboard audio processing chip rockchip-es8388 mentioned above.

  • controlC1：used for sound card control, C1 stands for sound card 1, corresponding to the HDMI sound output above.

  • pcmC0D0p：pcm device used for playback. The last "p" is the abbreviation of playback, which means playing sound.

  • pcmC0D0c：pcm device for recording. The last "c" is the abbreviation of capture, which means recording.

  • pcmC1D0p：pcm device used for playback. The last "p" is the abbreviation of playback, which means playing sound.

  • timer ：timer

  • by-path: stores the corresponding relationship of devices

root@lubancat:~# ls -l /dev/snd/by-path/
total 0
lrwxrwxrwx 1 root root 12 Feb 14 18:11 platform-fd880000.usb-usb-0:1.4:1.2 -> ../controlC2
lrwxrwxrwx 1 root root 12 Feb 14 18:11 platform-hdmi-sound -> ../controlC0
lrwxrwxrwx 1 root root 12 Feb 14 18:11 platform-rk809-sound -> ../controlC1
root@lubancat:~#
  • You can see that there is a corresponding relationship between each control, and these corresponding relationships just correspond to card 0 and card 1 above.

Recording and playback

Command Line

recording

The recording uses the arecord command, as shown below:


#获取录音设备
arecord -l
#用声卡0录制10s音频
arecord -d 10 -D hw:0,0 -r 48000 -c 2 -f S16_LE -t wav /data/test_device.wav

Parameter details:

  • -d 10 : Set the recording duration to 10 seconds.
  • -D hw:0,0 : specifies the audio device. hw:0,0 means using the first device (0) of the first sound card (0)
  • -r 48000 : Set the sampling rate to 48000 Hz (i.e. 48 kHz)
  • -c 2 : Set the number of audio channels to 2 (stereo)
  • -fS16_LE : Set the audio format to 16-bit signed little endian format (Signed 16-bit Little Endian)
  • -t wav : Set the output file format to WAV
  • /data/test_device.wav specifies the path and name of the output file

Audio Playback

#获取播放设备
aplay -l
#用声卡0播放音频5s
aplay -Dhw:1,0 -d5 /data/test_device.wav

Parameter details:

  • -D hw:0,0 : specifies the audio device, indicating the use of the first device (0) of the first sound card (0)
  • -d 5 : Set the playback duration to 5 seconds
  • /data/test_device.wav : specifies the path of the audio file to be played

Record and play simultaneously

Using arecord and aplay

#使用card 0录制并使用card 0进行播放
arecord -f cd -Dhw:0 | aplay -Dhw:0

Desktop

recording

After ensuring that you are connected to the Internet, install the recording software

#安装软件
sudo apt install gnome-sound-recorder

Open the software

AUDIO_2

Click record in the upper left corner of the application to start recording, and press done to end recording. The recording path is /home/linaro/.local/share/org.gnome.SoundRecorder/. If there is nothing in the waveform during recording, check whether the following headphones are properly plugged in.

AUDIO_3

Play Music

The system comes with Rhythmbox. If you need other players, you can download them yourself.

AUDIO_5

After opening, you need to import the audio, as shown in the figure:

AUDIO_6