From bc0e5ed4323d8a8358875231c9ff32858f1ac63e Mon Sep 17 00:00:00 2001
From: Lotus CI <ci@lotusguild.org>
Date: Mon, 14 Sep 2026 21:10:11 -0400
Subject: [PATCH] =?UTF-8?q?fix(lotus):=20capture=20the=20microphone=20mono?=
 =?UTF-8?q?=20=E2=80=94=20stereo=20interfaces=20published=20left-only=20on?=
 =?UTF-8?q?=20Firefox?=
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audioCaptureDefaults set no channelCount, so Firefox captured a 2-channel
audio interface (Scarlett Solo, one XLR mic on input 1) as stereo and,
with browser audio processing off (the ML denoise tier), published it as
is: peers heard the speaker in the left ear only. Chrome downmixes such
captures itself, which is why it only showed on Firefox. Request
channelCount: 1 for mic capture; screenshare audio is captured separately
and is unaffected. Tested. Bumps to 0.25.0-lotus.3.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA
---
 embedded/web/package.json                              |  2 +-
 src/lotus/lotusAudioConstraints.test.ts                | 10 ++++++++++
 .../CallViewModel/remoteMembers/ConnectionFactory.ts   |  7 +++++++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/embedded/web/package.json b/embedded/web/package.json
index e7dfcc2e..b0e03a9c 100644
--- a/embedded/web/package.json
+++ b/embedded/web/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@lotusguild/element-call-embedded",
-  "version": "0.25.0-lotus.2",
+  "version": "0.25.0-lotus.3",
   "files": [
     "README.md",
     "LICENSE-AGPL-3.0",
diff --git a/src/lotus/lotusAudioConstraints.test.ts b/src/lotus/lotusAudioConstraints.test.ts
index 90d66591..effac8d0 100644
--- a/src/lotus/lotusAudioConstraints.test.ts
+++ b/src/lotus/lotusAudioConstraints.test.ts
@@ -88,6 +88,16 @@ afterEach(() => {
 });
 
 describe("[lotus] audio-capture URL param overrides", () => {
+  test("mic capture is always requested mono (stereo interfaces on Firefox published L-only)", () => {
+    getUrlParams.mockReturnValue({
+      echoCancellation: false,
+      noiseSuppression: false,
+      autoGainControl: false,
+    });
+    createRoom();
+    expect(capturedAudioDefaults()).toMatchObject({ channelCount: 1 });
+  });
+
   test("with params defaulted to true, the Settings govern (upstream behaviour)", () => {
     getUrlParams.mockReturnValue({
       echoCancellation: true,
diff --git a/src/state/CallViewModel/remoteMembers/ConnectionFactory.ts b/src/state/CallViewModel/remoteMembers/ConnectionFactory.ts
index c8aae360..b4c083a4 100644
--- a/src/state/CallViewModel/remoteMembers/ConnectionFactory.ts
+++ b/src/state/CallViewModel/remoteMembers/ConnectionFactory.ts
@@ -183,6 +183,13 @@ function generateRoomOption({
     audioCaptureDefaults: {
       ...liveKitOptions.audioCaptureDefaults,
       deviceId: devices.audioInput.selected$.value?.id,
+      // [lotus] Voice is mono. Without this, Firefox captures a 2-channel
+      // audio interface (e.g. a Scarlett Solo with one XLR mic on input 1) as
+      // stereo and, with browser audio processing off, publishes it that way —
+      // peers hear the speaker in the left ear only. Chrome downmixes such
+      // captures itself, which is why it only showed on Firefox. Screenshare
+      // audio is captured separately and is unaffected.
+      channelCount: 1,
       echoCancellation:
         echoCancellationSetting.getValue() &&
         getUrlParams().echoCancellation !== false,