PicoKVM HDMI audio support

2025-12-31 14:37

Hey All,
Is there any documentation available on the PicoKVM board’s HDMI audio support? The product page says it has audio over HDMI capability, but from what I’ve tested and read, it seems like audio capture only works when using a USB audio device—not through HDMI.

I’m trying to understand whether this is a software/firmware limitation or a hardware limitation. For example, could a future firmware update enable true audio over HDMI? I haven’t been able to find clear documentation on how the HDMI signal is routed to the SoC, so I’m unsure whether it’s possible to get audio directly from HDMI.

Thanks in advance!

2026-01-04 1:44

Hello, the HDMI function of picoKVM is confirmed to be capable of audio transmission. When connected to the host, it can recognize the HDMI sound card device. On picokvm, using alsa also allows you to see the corresponding sound card for HDMI. However, it has not been fully developed yet, so we have not mentioned the audio function of the HDMI interface in the product interface.
I'm not sure if other distributors have wrongly promoted this. At least, HDMI audio functionality is not supported currently.

2026-01-05 15:25

Crocodile wrote: ↑2026-01-04 1:44 Hello, the HDMI function of picoKVM is confirmed to be capable of audio transmission. When connected to the host, it can recognize the HDMI sound card device. On picokvm, using alsa also allows you to see the corresponding sound card for HDMI. However, it has not been fully developed yet, so we have not mentioned the audio function of the HDMI interface in the product interface.
I'm not sure if other distributors have wrongly promoted this. At least, HDMI audio functionality is not supported currently.

Thanks for the info true, I can see the alsa audio card and indeed I could capture some audio waveform. HDMI audio capture works via arecord, but pitch is ~1.292× too fast (1 kHz tone measured as ~1292 Hz), indicating missing HDMI audio clock recovery in the tc358743 → I2S driver. Hardware path is functional; clocking is incorrect.
Using commands below I was able to record 30 Seconds and playback without any issues. I was wondering how much this fix is priotrized and if we can contribute to fix it and have audio inside kvm app.
arecord -D hw:0,0 -f S16_LE -c 2 -r 48000 -d 30 test.wav
scp [email protected]:/root/test.wav .
cat test.wav | sox -t raw -r 48000 -c 2 -e signed -b 16 - -d speed 0.774