HDMI eARC on Khadas VIM4 and VIM3L: Where Kernel Support Actually Stands
Hardware says yes; the kernel says not yet
Both the Khadas VIM4 (Amlogic A311D2) and the VIM3L (Amlogic S905D3) have eARC wired to the HDMI connector at the silicon level. That much is documented and not in dispute. The problem is on the software side, where Linux kernel support for eARC on Amlogic SoCs has lagged behind the hardware for years — and as of mid-2026, a fully functional, out-of-the-box eARC stack on either board does not exist in any mainstream kernel build.
What eARC actually is
eARC — Enhanced Audio Return Channel — was introduced with HDMI 2.1. It lets a TV send audio back to an AV receiver or soundbar over the same HDMI cable, instead of a separate optical or analog connection. The key difference from plain ARC is bandwidth: eARC runs at up to 37 Mbps, enough to carry uncompressed Dolby TrueHD, DTS-HD Master Audio, and object-based formats like Dolby Atmos and DTS:X. ARC maxes out around 1 Mbps and can only pass compressed audio.
For an SBC like the VIM4 used as an HTPC, eARC is the clean way to get lossless multichannel audio out to a receiver without an external DAC or USB audio adapter.
The VIM3L story: S905D3 and the unfinished kernel code
The VIM3L launched in 2019 with an explicit HTPC pitch — Khadas positioned it against streaming boxes and media players in their launch materials. eARC was listed as a feature. The Amlogic S905D3 SoC does have the eARC block, and the signals are routed to the HDMI port.
Community testing against the vendor kernel (4.9-based) found eARC code present but effectively at stub level. There were register settings and driver scaffolding, but no complete, tested path for negotiating the eARC link, handling discovery, or routing audio through it. Members on the Khadas forum traced through the Amlogic BSP source and confirmed the feature was not finished in that kernel branch.
Amlogic’s 5.4-based kernel improved the HDMI subsystem considerably, and the eARC-related code is more complete. But confirmed working reports from actual users have stayed scarce. The usual problem: getting the board to correctly negotiate eARC with a TV or receiver, set up the proper ALSA device, and route audio through it end-to-end requires all the pieces to be present and correctly integrated — and that integration work has not landed in a usable state.
VIM4: same picture, newer silicon
The VIM4 runs the A311D2, a more recent Amlogic chip, and it too has eARC at the hardware level. Questions on the Khadas forum about VIM4 eARC have mostly gone unanswered or received responses that amount to “hardware is there, no confirmed working implementation.” A thread from 2026 specifically asking about Ubuntu driver support on the VIM4 got no positive reports.
CEC on the VIM4 is in a similar position — present in hardware, partially implemented in software, but the default kernel interface is not the standard Linux CEC API that most userspace tools expect. eARC is one step further out than CEC in terms of driver maturity.
Where mainline Linux stands
The mainline Linux kernel’s Amlogic (Meson) DRM driver has been growing steadily. Contributors have done significant work on HDMI output and audio. But eARC is a separate, complex feature involving its own discovery protocol over a dedicated channel, and it has not been part of that mainline effort in any visible way.
The HDMI Codec framework in the DRM subsystem has seen recent work, and patches for HDMI audio on other SoCs — like Rockchip RK3588 — have landed. Amlogic-specific eARC is not there yet. If you are running mainline or Armbian on a VIM4 or VIM3L and you need eARC today, you simply do not have it.
What you can do instead
Standard HDMI audio output works fine on both boards. You can get PCM stereo and, in most configurations, compressed multichannel (AC3/DTS) over HDMI passthrough — which covers a lot of real-world use cases. If you just want audio to pass back to a soundbar and your setup supports regular ARC, that is a different code path and does not depend on the eARC driver stack.
For genuine lossless multichannel audio today, USB audio interfaces or I2S DAC boards remain the practical options while eARC driver work matures. Not the clean single-cable answer eARC promises, but it works.
Will this change?
Possibly. Amlogic has historically moved slowly on open-source kernel contributions, and eARC is a niche feature even among HDMI 2.1 users. The most plausible path to working eARC on these boards is either a focused community driver effort or Amlogic completing the feature in a vendor kernel that Khadas ships downstream — neither of which has a public roadmap right now.
Watching the Khadas forum threads on this topic remains the best early-warning system for when something actually changes.
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