Audio

1 Audio System Overview

The MB-E30P development board is equipped with a complete audio processing system. Based on the RK3568J processor's integrated audio controller and the external ES8388 audio codec chip, it provides a variety of audio input/output interfaces and supports high-quality audio recording and playback.

1.1 Audio System Architecture

RK3568J I2S/PCM ←→ ES8388 Codec ←→ 音频接口
     ↓
   HDMI Audio ←→ HDMI 接口

1.2 Technical Specifications

ComponentSpecification
Main AudioRK3568J integrated audio controller
Audio CodecES8388 high-performance audio Codec
Digital InterfaceI2S, PCM, SPDIF
Sampling Rate8kHz ~ 192kHz
Bit Depth16bit, 24bit, 32bit
Signal-to-Noise Ratio>90dB (ES8388)
THD + N<0.1% @ 1kHz

2 Audio Interface Configuration

The development board provides multiple audio interfaces to meet different application needs:

Audio Input Interfaces

  • Onboard MIC: Built-in omnidirectional microphone, suitable for voice recording
  • Headphone MIC: 3.5mm headphone jack integrates microphone input
  • Line In: Supports external audio device input

Audio Output Interfaces

  • Headphone Output: 3.5mm standard headphone jack, supports stereo output
  • Speaker Output: Onboard speaker interface, supports mono output
  • HDMI Audio: Outputs digital audio via the HDMI interface
AUDIO

3 Sound Card Devices

3.1 Obtaining Recording Devices

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: the onboard audio processing chip rockchip-es8388. This chip exposes two recording interfaces: one for the onboard MIC and one for the headphone MIC.
  • card 0 is a device registered in Linux; we can call these interfaces through applications.

3.2 Obtaining Playback Devices

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: the 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.

3.3 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 indicates sound card 0, corresponding to the onboard audio processing chip rockchip-es8388 mentioned above.

  • controlC1: used for sound card control; C1 indicates sound card 1, corresponding to the HDMI audio output mentioned above.

  • pcmC0D0p: PCM device for playback; the trailing "p" stands for playback.

  • pcmC0D0c: PCM device for recording; the trailing "c" stands for capture.

  • pcmC1D0p: PCM device for playback; the trailing "p" stands for playback.

  • timer: timer device, used for time synchronization of audio playback and recording.

  • by-path: stores the corresponding relationships of the 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:~#
  • As you can see, each control has a corresponding relationship, and these relationships correspond exactly to card 0 and card 1 mentioned above.

4 Recording and Playback

4.1 Command Line

Recording

The arecord command is used for recording. The following is an example:


#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: sets the recording duration to 10 seconds.
  • -D hw:0,0: specifies the audio device; hw:0,0 means use the first device (0) of the first sound card (0).
  • -r 48000: sets the sampling rate to 48000 Hz (i.e., 48 kHz).
  • -c 2: sets the number of audio channels to 2 (stereo).
  • -f S16_LE: sets the audio format to 16-bit signed little-endian (Signed 16-bit Little Endian).
  • -t wav: sets 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; means use the first device (0) of the first sound card (0).
  • -d 5: sets the playback duration to 5 seconds.
  • /data/test_device.wav: specifies the path of the audio file to play.

Recording and Playing Simultaneously

Using both arecord and aplay tools:

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

4.2 Desktop

Recording

After ensuring the network is connected, 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 app to start recording. Press "done" to end recording. The recording path is /home/linaro/.local/share/org.gnome.SoundRecorder/. If there is nothing on the waveform during recording, check whether the headphones are properly plugged in.

AUDIO_3

Playing Music

The software that comes with the system is 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

5 ALSA Advanced Configuration

Viewing Detailed Audio Device Information

# 查看所有音频设备
cat /proc/asound/cards

# 查看设备详细信息
cat /proc/asound/card0/id
cat /proc/asound/card1/id

# 查看 PCM 设备信息
cat /proc/asound/pcm

# 查看音频控制器信息
amixer -c 0 info
amixer -c 1 info

Audio Control and Mixing

# 查看所有音频控制
amixer -c 0 controls

# 查看音量控制
amixer -c 0 scontrols

# 设置主音量
amixer -c 0 sset 'Master' 80%

# 设置耳机音量
amixer -c 0 sset 'Headphone' 70%

# 设置麦克风增益
amixer -c 0 sset 'Mic' 60%

# 静音/取消静音
amixer -c 0 sset 'Master' mute
amixer -c 0 sset 'Master' unmute

6 Common Troubleshooting

6.1 No Sound Output

Inspection Steps:

# 检查音频设备
aplay -l
lsmod | grep snd

# 检查音量设置
amixer -c 0 scontrols
amixer -c 0 sget Master

# 测试音频输出
speaker-test -c 2 -t wav

# 检查音频服务
pulseaudio --check -v

6.2 No Sound or Noise During Recording

Solutions:

# 检查录音设备
arecord -l

# 调整麦克风增益
amixer -c 0 sset 'Mic' 70%
amixer -c 0 sset 'Capture' 80%

# 测试录音
arecord -D hw:0,0 -f cd test.wav

6.3 Audio Latency Issues

Optimization Configuration:

# 减少缓冲区大小
echo 'defaults.pcm.dmix.period_size 512' >> ~/.asoundrc
echo 'defaults.pcm.dmix.periods 2' >> ~/.asoundrc

# 使用低延迟内核
sudo apt-get install linux-lowlatency

6.4 No HDMI Audio Output

Inspection and Repair:

# 检查 HDMI 音频设备
aplay -l | grep HDMI

# 切换到 HDMI 音频输出
pactl set-default-sink alsa_output.platform-hdmi-sound.stereo-fallback

# 测试 HDMI 音频
aplay -D hw:1,0 test.wav