wt-publish: force explicit AAC-LC stereo mapping

crates/ec-node/src/main.rs

@@ -6312,6 +6312,10 @@ async fn wt_publish(args: WtPublishArgs) -> Result<()> {
 
     if args.transcode {
         cmd.args([
+            "-map",
+            "0:v:0",
+            "-map",
+            "0:a:0?",
             "-c:v",
             "libx264",
             "-preset",
@@ -6332,8 +6336,10 @@ async fn wt_publish(args: WtPublishArgs) -> Result<()> {
             "1",
             "-c:a",
             "aac",
+            "-profile:a",
+            "aac_low",
             "-b:a",
-            "128k",
+            "160k",
             "-ac",
             "2",
             "-ar",

evolution/proposals/ECP-0077-explicit-aac-transcode-profile.md

@@ -0,0 +1,27 @@
+# ECP-0077: Explicit AAC-LC Live Audio Profile In `wt-publish`
+
+## Context
+
+Live OTA inputs expose multiple AC-3 audio tracks (5.1 + stereo language variants). Browser watcher behavior is more stable when the published relay stream has a single explicit AAC-LC stereo track shape.
+
+## Decision
+
+In `ec-node wt-publish` transcode mode, force explicit stream mapping and AAC profile:
+
+- `-map 0:v:0`
+- `-map 0:a:0?`
+- `-c:a aac`
+- `-profile:a aac_low`
+- `-b:a 160k`
+- `-ac 2`
+- `-ar 48000`
+
+## Rationale
+
+- Removes ambiguity from ffmpeg auto stream selection when multiple audio tracks exist.
+- Keeps audio encoding browser-friendly and deterministic.
+- Preserves optional audio behavior (`0:a:0?`) for edge cases where input temporarily lacks audio.
+
+## Reversibility
+
+- Revert to ffmpeg auto mapping/profile by removing explicit `-map` and `-profile:a` flags.