From: GitHub pull_request - opened <github@alsa-project.org>
To: alsa-devel@alsa-project.org
Subject: USB-Audio: Scarlett 18i20 fix ADAT capture channel count for Gen 1/2
Date: Mon, 23 Mar 2026 12:12:29 +0100 (CET) [thread overview]
Message-ID: <189f7405e5e2b200-webhooks-bot@alsa-project.org> (raw)
In-Reply-To: <alsa-project/alsa-ucm-conf/pr/731@alsa-project.org>
alsa-project/alsa-ucm-conf pull request #731 was opened from codeurge:
The Scarlett 18i20 Gen 1 (0x800c) and Gen 2 (0x8201) have 18 capture
channels, but the ADAT Optical Input device ("Direct 2") unconditionally
maps 8 channels (indices 12-19). Channel indices 18 and 19 exceed the
available capture channels, causing WirePlumber/PipeWire to reject the
UCM profile with:
```
spa.alsa: Error in ALSA UCM profile for _ucm0003.hw:USB,0 (Direct2):
CaptureChannel6=18 >= CaptureChannels=18
spa.alsa: Error in ALSA UCM profile for _ucm0003.hw:USB,0 (Direct2):
CaptureChannel7=19 >= CaptureChannels=18
spa.alsa: Errors in ALSA UCM profile for card Scarlett 18i20 USB
```
This conditionally sizes the ADAT capture device based on
`DirectCaptureChannels` (already set per generation in the main conf):
- Gen 1/2 (18 channels): 6-channel ADAT capture (indices 12-17)
- Gen 3+ (20+ channels): 8-channel ADAT capture (indices 12-19)
Uses the same `If` conditional pattern as `Scarlett-2i-HiFi.conf`.
Tested on a Scarlett 18i20 Gen 2 (USB1235:8201) with PipeWire 1.4 and
WirePlumber on CachyOS (kernel 6.19.9). UCM profile loads cleanly with
no errors after the fix.
Request URL : https://github.com/alsa-project/alsa-ucm-conf/pull/731
Patch URL : https://github.com/alsa-project/alsa-ucm-conf/pull/731.patch
Repository URL: https://github.com/alsa-project/alsa-ucm-conf
parent reply other threads:[~2026-03-23 11:13 UTC|newest]
Thread overview: expand[flat|nested] mbox.gz Atom feed
[parent not found: <alsa-project/alsa-ucm-conf/pr/731@alsa-project.org>]
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