fix(audio): prebuffer live wav stream startup

Buffer a couple of live wav chunks before beginning playback so startup jitter is reduced when the stream first begins feeding speakers.

station_broadcast.lua

@@ -2,7 +2,7 @@
 -- ============================================================================
 -- 1. Configuration & Constants
 -- ============================================================================
-local APP_VERSION_TEXT = "v1.0.13"
+local APP_VERSION_TEXT = "v1.0.14"
 
 local CONFIG = {
     CLOUD_URL = "ws://stabadmin.fse-media.group",
@@ -14,6 +14,7 @@ local CONFIG = {
     DISK_AUDIO_STATION = "disk/Audio/Station/",
     STATION_IDENTITY_FILE = "station_identity.cfg",
     AUDIO_VOLUME = 3,
+    AUDIO_STREAM_PREROLL_CHUNKS = 2,
     DEBUG = true
 }
 
@@ -739,6 +740,14 @@ function Audio.createStream()
         end
         return table.remove(chunks, 1)
     end
+
+    stream.count = function()
+        return #chunks
+    end
+
+    stream.isFinished = function()
+        return finished
+    end
     
     return stream
 end
@@ -1393,8 +1402,10 @@ function Audio.playWavStreamItem(item)
 
     local playSeq = State.interruptSeq
     local source = item.audioData
+    local streamObj = nil
 
     if type(source) == "table" and source.read then
+        streamObj = source
         source = source.read
     end
 
@@ -1407,6 +1418,22 @@ function Audio.playWavStreamItem(item)
         end
     end
 
+    local prebufferChunks = math.max(0, tonumber(CONFIG.AUDIO_STREAM_PREROLL_CHUNKS) or 0)
+    if streamObj and prebufferChunks > 0 then
+        Utils.log("INFO", "Prebuffering live WAV stream: target chunks=" .. tostring(prebufferChunks))
+        while streamObj.count() < prebufferChunks and not streamObj.isFinished() do
+            if shouldStop(playSeq) then
+                Audio.stop("current")
+                return
+            end
+            if not waitForInterruptibleDelay(playSeq, 0.02) then
+                Audio.stop("current")
+                return
+            end
+        end
+        Utils.log("INFO", "Live WAV prebuffer ready: chunks=" .. tostring(streamObj.count()))
+    end
+
     while true do
         if shouldStop(playSeq) then
             Audio.stop("current")