ver0.1

app/services/audio_wav.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import array
 import io
 import shutil
 import subprocess
@@ -9,12 +10,57 @@ import wave
 from typing import Final
 
 _BAIDU_RATE: Final[int] = 16000
+# 诊室麦克风常见音量偏小，百度短语音 3301「语音质量错误」多与有效幅度过低有关。
+_NORM_TARGET_PEAK: Final[int] = 12000
+_NORM_MAX_GAIN: Final[float] = 80.0
 
 
 class WavDecodeError(ValueError):
     """Uploaded bytes are not a valid WAV or cannot be converted."""
 
 
+def pcm_s16le_to_wav_bytes(pcm: bytes, *, sample_rate: int = _BAIDU_RATE) -> bytes:
+    """将 raw s16le mono PCM 打成标准 WAV，供百度 ``format=wav`` 重试等场景。"""
+    if not pcm:
+        raise WavDecodeError("Empty PCM")
+    buf = io.BytesIO()
+    with wave.open(buf, "wb") as wf:
+        wf.setnchannels(1)
+        wf.setsampwidth(2)
+        wf.setframerate(sample_rate)
+        wf.writeframes(pcm)
+    return buf.getvalue()
+
+
+def normalize_pcm_s16le_for_baidu(pcm: bytes) -> bytes:
+    """提升过弱信号幅度，降低 err_no=3301（speech quality）概率；已足够响的音频不改。"""
+    if len(pcm) < 2 or len(pcm) % 2 != 0:
+        return pcm
+    samples = array.array("h")
+    samples.frombytes(pcm)
+    if not samples:
+        return pcm
+    peak = 0
+    for s in samples:
+        a = abs(int(s))
+        if a > peak:
+            peak = a
+    if peak == 0 or peak >= _NORM_TARGET_PEAK:
+        return pcm
+    scale = min(_NORM_MAX_GAIN, float(_NORM_TARGET_PEAK) / float(peak))
+    if scale <= 1.0:
+        return pcm
+    out = array.array("h")
+    for s in samples:
+        v = int(round(float(s) * scale))
+        if v > 32767:
+            v = 32767
+        elif v < -32768:
+            v = -32768
+        out.append(v)
+    return out.tobytes()
+
+
 def wav_bytes_to_pcm16k_mono_s16le(wav_bytes: bytes) -> bytes:
     """
     Prefer ffmpeg for arbitrary channel count / sample rate.
@@ -57,7 +103,7 @@ def _ffmpeg_to_pcm16k(wav_bytes: bytes, ffmpeg: str) -> bytes:
         raise WavDecodeError(f"ffmpeg wav decode failed: {err or proc.returncode}")
     if not proc.stdout:
         raise WavDecodeError("ffmpeg produced empty PCM")
-    return proc.stdout
+    return normalize_pcm_s16le_for_baidu(proc.stdout)
 
 
 def _stdlib_wave_to_pcm16k(wav_bytes: bytes) -> bytes:
@@ -96,6 +142,6 @@ def _stdlib_wave_to_pcm16k(wav_bytes: bytes) -> bytes:
             l_s, r_s = struct.unpack("<hh", chunk)
             m = max(min((l_s + r_s) // 2, 32767), -32768)
             out.extend(struct.pack("<h", m))
-        return bytes(out)
+        return normalize_pcm_s16le_for_baidu(bytes(out))
 
-    return raw
+    return normalize_pcm_s16le_for_baidu(raw)