feat(audio): 实现流式WAV解码器并优化音频播放逻辑

将应用版本更新至v1.0.48；新增WAV头部解析与流式解码逻辑，替换原有的单块解码方案；添加扬声器speakWav兼容性检测，无支持设备时输出错误日志；优化WAV解码错误处理与日志输出，仅首次打印音频格式信息。

station_broadcast.lua

@@ -1,6 +1,6 @@
 
 -- 1. Configuration & Constants
-local APP_VERSION_TEXT = "v1.0.47"
+local APP_VERSION_TEXT = "v1.0.48"
 
 local CONFIG = {
     CLOUD_URL = "ws://stabadmin.fse-media.group",
@@ -1350,6 +1350,152 @@ local function decodeWavChunkToSamples(chunk)
     }
 end
 
+local function parseWavHeader(buf)
+    if type(buf) ~= "string" or #buf < 44 then
+        return nil, nil, "wav header too short"
+    end
+    if buf:sub(1, 4) ~= "RIFF" or buf:sub(9, 12) ~= "WAVE" then
+        return nil, nil, "invalid wav header"
+    end
+
+    local offset = 13
+    local audioFormat, channels, sampleRate, bitsPerSample
+    local dataOffset, dataSize
+
+    while offset + 7 <= #buf do
+        local chunkId = buf:sub(offset, offset + 3)
+        local chunkSize = readU32LE(buf, offset + 4)
+        if not chunkSize then break end
+        local payloadOffset = offset + 8
+        if chunkId == "fmt " and chunkSize >= 16 then
+            audioFormat = readU16LE(buf, payloadOffset)
+            channels = readU16LE(buf, payloadOffset + 2)
+            sampleRate = readU32LE(buf, payloadOffset + 4)
+            bitsPerSample = readU16LE(buf, payloadOffset + 14)
+        elseif chunkId == "data" then
+            dataOffset = payloadOffset
+            dataSize = chunkSize
+            break
+        end
+        offset = payloadOffset + chunkSize
+        if chunkSize % 2 == 1 then
+            offset = offset + 1
+        end
+    end
+
+    if audioFormat ~= 1 then
+        return nil, nil, "unsupported wav format " .. tostring(audioFormat)
+    end
+    if channels ~= 1 and channels ~= 2 then
+        return nil, nil, "unsupported channels " .. tostring(channels)
+    end
+    if bitsPerSample ~= 8 and bitsPerSample ~= 16 then
+        return nil, nil, "unsupported bits " .. tostring(bitsPerSample)
+    end
+    if not dataOffset or not dataSize then
+        return nil, nil, "wav missing data chunk"
+    end
+
+    return {
+        channels = channels,
+        bitsPerSample = bitsPerSample,
+        sampleRate = sampleRate or 0,
+        dataSize = dataSize
+    }, dataOffset, nil
+end
+
+local function decodePcmBytesToSamples(pcm, channels, bitsPerSample)
+    if type(pcm) ~= "string" or #pcm == 0 then return {} end
+    local frameSize = channels * (bitsPerSample / 8)
+    if frameSize <= 0 then return {} end
+    local usableLen = #pcm - (#pcm % frameSize)
+    if usableLen <= 0 then return {} end
+
+    local samples = {}
+    local sampleIndex = 1
+    local endOffset = usableLen - frameSize + 1
+
+    for pos = 1, endOffset, frameSize do
+        local mixed = 0
+        for ch = 0, channels - 1 do
+            local sampleOffset = pos + ch * (bitsPerSample / 8)
+            local sampleValue
+            if bitsPerSample == 8 then
+                local raw = string.byte(pcm, sampleOffset)
+                sampleValue = (raw or 128) - 128
+            else
+                sampleValue = readS16LE(pcm, sampleOffset) or 0
+                if sampleValue >= 0 then
+                    sampleValue = math.floor(sampleValue / 256)
+                else
+                    sampleValue = math.ceil(sampleValue / 256)
+                end
+            end
+            mixed = mixed + sampleValue
+        end
+        samples[sampleIndex] = clampSample8(math.floor(mixed / channels))
+        sampleIndex = sampleIndex + 1
+    end
+
+    return samples
+end
+
+local function createWavStreamDecoder()
+    local state = {
+        header = nil,
+        headerParsed = false,
+        pending = "",
+        frameSize = 0,
+        logged = false
+    }
+
+    local function decode(chunk)
+        if type(chunk) ~= "string" or #chunk == 0 then return {}, nil, state.header end
+
+        local buf = state.pending .. chunk
+        state.pending = ""
+
+        if not state.headerParsed then
+            local header, dataOffset, err = parseWavHeader(buf)
+            if err then
+                state.pending = buf
+                if #state.pending > 128 * 1024 then
+                    return nil, err, nil
+                end
+                return {}, "need header", nil
+            end
+
+            state.header = header
+            state.headerParsed = true
+            state.frameSize = (tonumber(header.channels) or 1) * ((tonumber(header.bitsPerSample) or 16) / 8)
+            buf = buf:sub(dataOffset)
+        end
+
+        local frameSize = tonumber(state.frameSize) or 0
+        if frameSize <= 0 then return nil, "invalid frame size", state.header end
+
+        local usableLen = #buf - (#buf % frameSize)
+        local usable = ""
+        if usableLen > 0 then
+            usable = buf:sub(1, usableLen)
+        end
+        local rest = buf:sub(usableLen + 1)
+        if rest and rest ~= "" then
+            state.pending = rest
+        end
+
+        local samples = decodePcmBytesToSamples(
+            usable,
+            tonumber(state.header and state.header.channels) or 1,
+            tonumber(state.header and state.header.bitsPerSample) or 16
+        )
+
+        return samples, nil, state.header
+    end
+
+    return { decode = decode }
+end
+
 local function areHqSpeakersBusy(speakers)
     for _, sp in ipairs(speakers) do
         local playing = false
@@ -1515,6 +1661,18 @@ local function pushWavChunkToSpeakers(payload, playSeq)
         end
     end
 
+    local hasFallback = false
+    for _, sp in ipairs(Peripherals.speakers or {}) do
+        if type(sp.speakWav) == "function" then
+            hasFallback = true
+            break
+        end
+    end
+    if not hasFallback then
+        Utils.log("ERROR", "No speaker supports speakWav/speakWavAll for WAV chunk fallback")
+        return false
+    end
+
     local pending = {}
     for _, sp in ipairs(Peripherals.speakers or {}) do
         local name = peripheral.getName(sp)
@@ -1670,6 +1828,8 @@ function Audio.playWavStreamItem(item)
         Utils.log("INFO", "Live WAV prebuffer ready: chunks=" .. tostring(streamObj.count()))
     end
 
+    local wavDecoder = createWavStreamDecoder()
+
     while true do
         if shouldStop(playSeq) then
             Audio.stop("current")
@@ -1679,24 +1839,28 @@ function Audio.playWavStreamItem(item)
         local chunk = source()
         if chunk == nil then break end
         if type(chunk) == "string" and #chunk > 0 then
-            local samples, err, meta = decodeWavChunkToSamples(chunk)
+            local samples, err, meta = wavDecoder.decode(chunk)
             if samples and #samples > 0 then
-                Utils.log("INFO", string.format(
+                if meta and not wavDecoder.logged then
-                    "Decoded WAV chunk: bytes=%d samples=%d rate=%d ch=%d bits=%d",
+                    wavDecoder.logged = true
-                    #chunk,
+                    Utils.log("INFO", string.format(
-                    #samples,
+                        "WAV stream header: rate=%d ch=%d bits=%d",
-                    tonumber(meta and meta.sampleRate) or 0,
+                        tonumber(meta and meta.sampleRate) or 0,
-                    tonumber(meta and meta.channels) or 0,
+                        tonumber(meta and meta.channels) or 0,
-                    tonumber(meta and meta.bitsPerSample) or 0
+                        tonumber(meta and meta.bitsPerSample) or 0
-                ))
+                    ))
+                end
                 local playOk = playChunkOnSpeakers(samples, CONFIG.AUDIO_VOLUME, playSeq, false)
                 if not playOk then
                     Audio.stop("current")
                     return
                 end
-            else
+            elseif err and err ~= "need header" then
-                Utils.log("WARN", "WAV chunk decode failed, falling back to HQ path: " .. tostring(err))
+                Utils.log("ERROR", "WAV stream decode failed: " .. tostring(err))
-                if not pushWavChunkToSpeakers(chunk, playSeq) then
+                Audio.stop("current")
+                return
+            elseif err == "need header" then
+                if not waitForInterruptibleDelay(playSeq, 0.01) then
                     Audio.stop("current")
                     return
                 end