fix: 修复 SenseVoice argmax 偏移 bug + 添加调试音频保存

修复转写结果显示为 token ID 的问题：argmax() 返回的是扁平化数组的
绝对索引，需减去 offset 才能得到正确的 token ID。同时修正置信度
计算使用正确的绝对索引。

添加调试音频保存功能：开启后每次推理将原始 PCM 保存为 WAV 文件
到 /tmp/impress_audio_debug/，并增加 RMS 电平和 NaN 诊断日志。

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/audio/audio_decoder.cpp

@@ -7,7 +7,7 @@
 #define DR_WAV_IMPLEMENTATION
 #define DR_MP3_IMPLEMENTATION
 #define DR_FLAC_IMPLEMENTATION
-#include <dr_wav.h>
+#include "dr_wav.h"
 #include <dr_mp3.h>
 #include <dr_flac.h>
 #endif

src/core/sense_voice_engine.cpp

@@ -12,6 +12,10 @@
 #include <QMutex>
 #include <QMutexLocker>
 #include <QFileInfo>
+#include <QDir>
+#include <QDateTime>
+#include <QFile>
+#include <QDataStream>
 #include <algorithm>
 #include <cmath>
 
@@ -22,6 +26,54 @@
 
 static const char* const kTag = "SenseVoiceEngine";
 
+/**
+ * @brief 简易 WAV 写入（不依赖 dr_wav，避免多定义冲突）
+ */
+static bool saveWav16(const QString& path, const std::vector<float>& samples, int sampleRate) {
+    QFile file(path);
+    if (!file.open(QIODevice::WriteOnly)) return false;
+
+    int numSamples = static_cast<int>(samples.size());
+    int dataSize = numSamples * 2; // 16-bit mono
+    int totalSize = 36 + dataSize; // RIFF header size
+    quint16 audioFormat = 1; // PCM
+    quint16 numChannels = 1;
+    quint32 byteRate = sampleRate * 2; // sampleRate * numChannels * bitsPerSample/8
+    quint16 blockAlign = 2; // numChannels * bitsPerSample/8
+    quint16 bitsPerSample = 16;
+
+    QDataStream out(&file);
+    out.setByteOrder(QDataStream::LittleEndian);
+
+    // RIFF header
+    out.writeRawData("RIFF", 4);
+    out << static_cast<quint32>(totalSize);
+    out.writeRawData("WAVE", 4);
+
+    // fmt chunk
+    out.writeRawData("fmt ", 4);
+    out << static_cast<quint32>(16); // chunk size
+    out << audioFormat;
+    out << numChannels;
+    out << static_cast<quint32>(sampleRate);
+    out << byteRate;
+    out << blockAlign;
+    out << bitsPerSample;
+
+    // data chunk
+    out.writeRawData("data", 4);
+    out << static_cast<quint32>(dataSize);
+
+    // PCM data (float → int16)
+    for (float s : samples) {
+        s = std::max(-1.0f, std::min(1.0f, s)); // clip
+        qint16 val = static_cast<qint16>(s * 32767.0f);
+        out << val;
+    }
+
+    return file.error() == QFile::FileError::NoError;
+}
+
 namespace impress {
 
 /** 语言代码映射 */
@@ -227,6 +279,11 @@ bool SenseVoiceEngine::isLoaded() const {
     return loaded_;
 }
 
+void SenseVoiceEngine::setDebugSaveAudio(bool enable) {
+    debugSaveAudio_ = enable;
+    LOG_INFO(kTag, QString("调试录音保存: %1").arg(enable ? "开启" : "关闭"));
+}
+
 /** CTC 贪婪解码：去重 + 去除空白 */
 static std::vector<int> ctcGreedyDecode(const std::vector<int>& tokens, int blankToken) {
     std::vector<int> result;
@@ -286,9 +343,53 @@ RecognitionResult SenseVoiceEngine::infer(const std::vector<float>& samples,
     try {
         // 1. 重采样到 16kHz
         Timer preprocessTimer;
+
+        // 调试模式：保存原始音频到 WAV 文件
+        if (debugSaveAudio_ && !samples.empty()) {
+            QString debugDir = "/tmp/impress_audio_debug";
+            QDir dir;
+            if (!dir.exists(debugDir)) {
+                dir.mkpath(debugDir);
+            }
+            QString timestamp = QDateTime::currentDateTime().toString("yyyyMMdd_HHmmss_zzz");
+            QString wavPath = QString("%1/audio_%2_%3Hz.wav")
+                .arg(debugDir).arg(timestamp).arg(sampleRate);
+
+            if (saveWav16(wavPath, samples, sampleRate)) {
+                LOG_DEBUG(kTag, QString("调试音频已保存: %1 (%2 样本, %3Hz)")
+                    .arg(wavPath).arg(samples.size()).arg(sampleRate));
+            } else {
+                LOG_WARNING(kTag, QString("无法创建调试音频文件: %1").arg(wavPath));
+            }
+        }
+
         std::vector<float> processedSamples = samples;
         int currentSampleRate = sampleRate;
 
+        // 计算输入音频 RMS 电平用于诊断
+        double rms = 0.0;
+        bool hasNaN = false;
+        for (float s : samples) {
+            if (std::isnan(s) || std::isinf(s)) { hasNaN = true; break; }
+            rms += s * s;
+        }
+        rms = std::sqrt(rms / samples.size());
+
+        if (hasNaN) {
+            result.text = "[错误] 输入音频包含 NaN/Inf 值，请检查麦克风设备";
+            result.latency_ms = timer.elapsedMs();
+            LOG_ERROR(kTag, QString("输入音频包含无效值 (NaN/Inf), 样本数: %1").arg(samples.size()));
+            return result;
+        }
+        if (rms < 1e-6) {
+            result.text = "";
+            result.latency_ms = timer.elapsedMs();
+            LOG_DEBUG(kTag, QString("静音段 (RMS: %1), 跳过推理").arg(rms, 0, 'f', 6));
+            return result;
+        }
+
+        LOG_DEBUG(kTag, QString("输入音频 RMS: %1 (样本数: %2)").arg(rms, 0, 'f', 6).arg(samples.size()));
+
         if (sampleRate != 16000) {
             AudioProcessor processor(16000);
             processedSamples = processor.resample(samples, sampleRate);
@@ -370,13 +471,14 @@ RecognitionResult SenseVoiceEngine::infer(const std::vector<float>& samples,
 
         for (int t = 0; t < seqLen; t++) {
             int offset = t * vocabSize;
-            int bestToken = argmax(logitsData, offset, offset + vocabSize);
+            int bestAbsIdx = argmax(logitsData, offset, offset + vocabSize);
+            int bestToken = bestAbsIdx - offset; // 绝对索引 → token ID
 
             if (bestToken != SenseVoiceTokenizer::kTokenBlank) {
                 rawTokens.push_back(bestToken);
 
                 // 计算置信度
-                float maxLogit = logitsData[offset + bestToken];
+                float maxLogit = logitsData[bestAbsIdx];
                 // 近似置信度: 使用 softmax 的最大值位置
                 totalConf += maxLogit;
                 confCount++;
@@ -398,8 +500,8 @@ RecognitionResult SenseVoiceEngine::infer(const std::vector<float>& samples,
             result.text = "";
         } else if (impl_->tokenizer.isLoaded()) {
             result.text = impl_->tokenizer.decode(decodedTokens);
-            LOG_DEBUG(kTag, QString("解码文本: %1 个 token → %2 字符")
+            LOG_DEBUG(kTag, QString("解码文本: %1 个 token → %2 字符: %3")
-                .arg(decodedTokens.size()).arg(result.text.length()));
+                .arg(decodedTokens.size()).arg(result.text.length()).arg(result.text));
         } else {
             // 降级：输出 token ID
             QString decodedText;

src/core/sense_voice_engine.h

@@ -48,6 +48,9 @@ public:
                             int sampleRate,
                             const QString& language = QString());
 
+    /** @brief 设置调试模式：开启后每次推理保存音频到 WAV */
+    void setDebugSaveAudio(bool enable);
+
 signals:
     void modelLoaded(const QString& modelPath);
     void modelLoadError(const QString& modelPath, const QString& error);
@@ -58,6 +61,7 @@ private:
     struct Impl;
     std::unique_ptr<Impl> impl_;
     bool loaded_ = false;
+    bool debugSaveAudio_ = false;
 };
 
 } // namespace impress