I am using the multmedia image for the IMX8MP EVK.
Image version LF_v6.6.3-1.0.0_images_IMX8MPEVK.zip.
When playing wave file to HDMI audio output, I cannot hear sound.
root@imx8mpevk:/# aplay -Dplughw:1,0 /usr/share/sounds/alsa/Front_Center.wav
Playing WAVE '/usr/share/sounds/alsa/Front_Center.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Mono
root@imx8mpevk:/# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: btscoaudio [bt-sco-audio], device 0: 30c20000.sai-bt-sco-pcm-wb bt-sco-pcm-wb-0 [30c20000.sai-bt-sco-pcm-wb bt-sco-pcm-wb-0]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: audiohdmi [audio-hdmi], device 0: i.MX HDMI i2s-hifi-0 [i.MX HDMI i2s-hifi-0]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 3: wm8960audio [wm8960-audio], device 0: HiFi wm8960-hifi-0 [HiFi wm8960-hifi-0]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 3: wm8960audio [wm8960-audio], device 1: HiFi-ASRC-FE (*) []
Subdevices: 1/1
Subdevice #0: subdevice #0
card 4: imxaudioxcvr [imx-audio-xcvr], device 0: XCVR PCM snd-soc-dummy-dai-0 [XCVR PCM snd-soc-dummy-dai-0]
Subdevices: 1/1
Subdevice #0: subdevice #0
root@imx8mpevk:/#
Please try to unblank the HDMI screen. e.g. echo 0 > /sys/class/graphics/fb2/blank (where fb2 is your hdmi screen).
If you are displaying something on screen, you don't need to unblank it. Otherwise, you need to unblank the screen before you play the audio.
You can run below command to keep it unblank after run the unblank command.
echo -ne "\033[9]" > /dev/tty0