Initial commit: Nat20 Notes — TTRPG session transcription & summarization

backend/app/pipeline/audio.py

@@ -0,0 +1,35 @@
+import subprocess
+from pathlib import Path
+
+from ..errors import AudioExtractionError
+from ..logging_config import get_logger
+
+log = get_logger(__name__)
+
+
+def extract_audio(video_path: Path, audio_path: Path) -> Path:
+    """Extract 16kHz mono wav from any video/audio container."""
+    if not video_path.exists():
+        raise AudioExtractionError(f"Uploaded file not found on disk at {video_path}. It may not have finished uploading, or the upload volume isn't mounted correctly.")
+
+    if audio_path.exists():
+        log.info("Audio already extracted at %s, skipping", audio_path)
+        return audio_path
+
+    log.info("Extracting audio: %s -> %s", video_path, audio_path)
+    result = subprocess.run(
+        [
+            "ffmpeg", "-y", "-i", str(video_path),
+            "-vn", "-acodec", "pcm_s16le", "-ar", "16000", "-ac", "1",
+            str(audio_path),
+        ],
+        capture_output=True, text=True,
+    )
+    if result.returncode != 0:
+        # surface ffmpeg's own error line rather than the whole verbose log
+        stderr_tail = "\n".join(result.stderr.strip().splitlines()[-5:])
+        raise AudioExtractionError(
+            f"ffmpeg failed to extract audio (exit code {result.returncode}). "
+            f"This usually means the file is corrupt or not a supported format. Last output:\n{stderr_tail}"
+        )
+    return audio_path