HLConvolver UPnP and direct ALSA engine feature upgrade

[Mitchco]

HLConvolver 2.8.1 is released.

HLConvolver is a headless convolution engine with a Web UI, systemd service integration, UPnP input/output support, managed ALSA routing, multichannel FIR processing, and optional DoP output.

Current packages are available for Ubuntu 24.04, and Raspberry Pi arm64 Bookworm.

Supported routes from the Web UI:

• alsa-local = ALSA Loopback input -> local ALSA playback
• alsa-upnp = ALSA Loopback input -> UPnP /live output
• upnp-upnp = UPnP MediaRenderer input -> UPnP /live output
• upnp-alsa = UPnP MediaRenderer input -> local ALSA playback
• local-local = local device I/O

UPnP input formats currently supported:

• WAV
• AIFF / AIFC
• FLAC

UPnP /live output bit depth:

• 16-bit
• 24-bit default
• 32-bit

DSD / DoP output is available on the upnp-alsa route:

• PCM default
• DoP
• DSD64 / DSD128 / DSD256
• First-order / second-order DSD noise shaper
• configurable DSD headroom
• optional fallback to PCM if DoP cannot open

Multichannel / routing notes:

• alsa-local supports up to 16 active input/output channels.
• upnp-alsa supports up to 16 active input/output channels.
• UPnP routes are software-configurable up to 16 active channels.
• Local ALSA output supports separate active input/output counts, such as 2 in / 4 out, 2 in / 6 out, and 2 in / 8 out.
• UPnP-output multichannel success depends on the downstream renderer and DAC.

UPnP MediaRenderer improvements in 2.8.1:

• elapsed/progress position reporting
• duration/media-info reporting
• natural end-of-track handling
• normal album/playlist advance with compatible controllers such as Audirvana and JRiver

Web UI / operation:

• Route selection, audio settings, DSD output settings, UPnP target selection, diagnostics, and log download are handled from the Web UI.
• Long loaded filter filenames now wrap correctly instead of being truncated.
• Service scripts handle normal runtime setup, including ALSA Loopback where required.

Recent validation examples:

On a preliminary Hang Loose Processor system using Raspberry Pi CM5 hardware, HLConvolver was tested with:

• 44.1 kHz input upsampled to a 705.6 kHz FIR path and DSD256 DoP output
• 16 channels of 65,536-tap FIR processing at 96 kHz
• 2 channels using a 65,536-tap FIR path at 705.6 kHz

Technical note:

HLConvolver includes a direct ALSA engine for the managed ALSA routes. It communicates directly with ALSA Loopback capture and the selected output device, handles sample-rate changes, and uses matching sample-rate FIR filters when configured. This is intended to avoid the drift and handoff problems that can occur in unmanaged loopback chains.

30-day free trial available. Enter 281 in the order notes field. All future upgrades are free with a license purchase.