07 Audio

1 Audio System Overview

GM-3568JHF development board is equipped with a complete audio processing system, based on the integrated audio controller of RK3568J processor and external ES8388 audio codec chip, providing multiple audio input and output interfaces, supporting high-quality audio recording and playback functions.

1.1 Audio System Architecture

RK3568J I2S/PCM ←→ ES8388 Codec ←→ Audio Interface
     ↓
   HDMI Audio ←→ HDMI Interface

1.2 Technical Specifications

ComponentSpecification
Main Control 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 Interface

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

Audio Output Interface

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

3 Sound Card Devices

3.1 Get 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: Onboard audio processing chip rockchip-es8388, this chip leads out two recording interfaces, one is the onboard MIC, and the other is the headphone MIC.
  • card 0 is a device registered in Linux, and we can call these interfaces through applications.

3.2 Get 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 : Onboard audio processing chip rockchip-es8388
  • card 1 : HDMI sound output

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

3.3 Sound Card Driver Directory

View 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 means sound card 0, corresponding to the onboard audio processing chip rockchip-es8388 mentioned above.
  • controlC1: Used for sound card control, C1 means sound card 1, corresponding to the HDMI sound output mentioned above.
  • pcmC0D0p: PCM device used for playback, the last "p" is the abbreviation of playback.
  • pcmC0D0c: PCM device used for recording, the last "c" is the abbreviation of capture.
  • pcmC1D0p: PCM device used for playback, the last "p" is the abbreviation of playback.
  • timer: Timer device, used for time synchronization of audio playback and recording.
  • by-path: Saves the correspondence 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 correspondence between each control, and these correspondences exactly correspond to card 0 and card 1 mentioned above.

4 Recording and Playback

4.1 Command Line

Recording

Recording uses the arecord command, an example is as follows:

# Get recording devices
arecord -l
# Record 10s audio with sound card 0
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 recording duration to 10 seconds.
  • -D hw:0,0 : Specify the audio device, hw:0,0 means using the first device (0) of the first sound card (0).
  • -r 48000 : Set sampling rate to 48000 Hz (i.e. 48 kHz).
  • -c 2 : Set the number of audio channels to 2 (stereo).
  • -f S16_LE : Set audio format to 16-bit signed little endian.
  • -t wav : Set output file format to WAV.
  • /data/test_device.wav : Specify the path and name of the output file.

Audio Playback

# Get playback devices
aplay -l
# Play audio for 5s with sound card 0
aplay -Dhw:1,0 -d5 /data/test_device.wav

Parameter details:

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

Recording while Playing

Use arecord and aplay tools.

# Record with card 0 and play with card 0
arecord -f cd -Dhw:0 | aplay -Dhw:0

4.2 Desktop

Recording

After ensuring the network is connected, install the recording software.

# Install software
sudo apt install gnome-sound-recorder

Open the software.

AUDIO_2

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

AUDIO_3

Playing Music

The system comes with Rhythmbox software. 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

View detailed audio device information

# View all audio devices
cat /proc/asound/cards

# View device detailed information
cat /proc/asound/card0/id
cat /proc/asound/card1/id

# View PCM device information
cat /proc/asound/pcm

# View audio controller information
amixer -c 0 info
amixer -c 1 info

Audio Control and Mixing

# View all audio controls
amixer -c 0 controls

# View volume controls
amixer -c 0 scontrols

# Set master volume
amixer -c 0 sset 'Master' 80%

# Set headphone volume
amixer -c 0 sset 'Headphone' 70%

# Set microphone gain
amixer -c 0 sset 'Mic' 60%

# Mute/Unmute
amixer -c 0 sset 'Master' mute
amixer -c 0 sset 'Master' unmute

6 Common Troubleshooting

6.1 No Sound Output

Check Steps:

# Check audio devices
aplay -l
lsmod | grep snd

# Check volume settings
amixer -c 0 scontrols
amixer -c 0 sget Master

# Test audio output
speaker-test -c 2 -t wav

# Check audio service
pulseaudio --check -v

6.2 Recording No Sound or Noise

Solution:

# Check recording devices
arecord -l

# Adjust microphone gain
amixer -c 0 sset 'Mic' 70%
amixer -c 0 sset 'Capture' 80%

# Test recording
arecord -D hw:0,0 -f cd test.wav

6.3 Audio Latency Issues

Optimization Configuration:

# Reduce buffer size
echo 'defaults.pcm.dmix.period_size 512' >> ~/.asoundrc
echo 'defaults.pcm.dmix.periods 2' >> ~/.asoundrc

# Use low latency kernel
sudo apt-get install linux-lowlatency

6.4 HDMI Audio No Output

Check and Fix:

# Check HDMI audio device
aplay -l | grep HDMI

# Switch to HDMI audio output
pactl set-default-sink alsa_output.platform-hdmi-sound.stereo-fallback

# Test HDMI audio
aplay -D hw:1,0 test.wav