feat: add chunked ASR for long audio with env-configurable chunk duration

- Integrate chunking into LocalAI client to avoid GPU OOM on long audio.
- Split long files into overlapping chunks; transcribe each chunk; merge segments with corrected timestamps.
- Auto-enable chunking when audio duration > LOCALAI_MAX_SINGLE_REQUEST_DURATION (default 300s).
- Add env variables:
    LOCALAI_CHUNK_DURATION (default 180)
    LOCALAI_CHUNK_OVERLAP (default 2)
    LOCALAI_MAX_SINGLE_REQUEST_DURATION (default 300)
- Add unit and integration tests for chunking logic.
- Confirmed working end-to-end with vibevoice-cpp-asr on 88-minute file.

tests/test_localai_chunking.py

@@ -0,0 +1,230 @@
+import os
+import json
+import tempfile
+from unittest.mock import patch, MagicMock
+
+import pytest
+
+from scraibe.localai_client import LocalAIClient, LocalAIError
+from scraibe.audio import get_audio_duration, split_audio_into_chunks
+
+
+TEST_AUDIO_1 = "tests/audio_test_1.mp4"
+
+
+def make_fake_segments(start=0.0, count=3):
+    segments = []
+    for i in range(count):
+        s = start + i * 2.0
+        e = s + 2.0
+        segments.append({
+            "start": s,
+            "end": e,
+            "speaker": "SPEAKER_00",
+            "text": f"Segment text {i}",
+        })
+    return segments
+
+
+def fake_localai_response(segments):
+    return {
+        "segments": segments,
+        "text": " ".join(seg["text"] for seg in segments),
+    }
+
+
+@pytest.fixture
+def client():
+    with patch.object(LocalAIClient, "__init__", lambda self, **kw: None):
+        c = LocalAIClient()
+        c.api_url = "http://localhost:8080"
+        c.model = "vibevoice-diarize"
+        c.api_key = None
+        c._client = MagicMock()
+        return c
+
+
+def test_parse_diarization_response(client):
+    segs = make_fake_segments()
+    raw = fake_localai_response(segs)
+
+    out = client._parse_diarization_response(raw)
+
+    assert "segments" in out
+    assert "speakers" in out
+    assert "transcripts" in out
+    assert len(out["segments"]) == len(segs)
+    for i, s in enumerate(segs):
+        assert out["segments"][i][0] == s["start"]
+        assert out["segments"][i][1] == s["end"]
+        assert out["speakers"][i] == s["speaker"]
+        assert out["transcripts"][i] == s["text"]
+
+
+def test_parse_diarization_empty(client):
+    out = client._parse_diarization_response({"segments": []})
+    assert out["segments"] == []
+    assert out["speakers"] == []
+    assert out["transcripts"] == []
+
+
+def test_diarize_and_transcribe_single_happy(client):
+    with patch.object(client, "_client") as mock_client:
+        mock_resp = MagicMock()
+        mock_resp.status_code = 200
+        mock_resp.json.return_value = fake_localai_response(make_fake_segments())
+        mock_client.post.return_value = mock_resp
+
+        result = client.diarize_and_transcribe(
+            audio_path=TEST_AUDIO_1,
+            verbose=False,
+            return_raw=True,
+        )
+
+        assert "segments" in result
+        assert "raw_result" in result
+        assert len(result["segments"]) > 0
+
+
+def test_chunking_triggered_for_long_audio(client):
+    # Simulate long audio by patching get_audio_duration
+    with patch("scraibe.localai_client.get_audio_duration") as mock_dur, \
+         patch.object(client, "_diarize_and_transcribe_chunked") as mock_chunked:
+
+        mock_dur.return_value = 600.0  # 10 minutes
+        mock_chunked.return_value = {
+            "segments": [],
+            "speakers": [],
+            "transcripts": [],
+        }
+
+        client.diarize_and_transcribe(
+            audio_path=TEST_AUDIO_1,
+            verbose=False,
+            use_chunking=None,
+            max_single_request_duration=300.0,
+        )
+
+        mock_chunked.assert_called_once()
+
+
+def test_chunking_not_triggered_for_short_audio(client):
+    with patch("scraibe.localai_client.get_audio_duration") as mock_dur, \
+         patch.object(client, "_diarize_and_transcribe_chunked") as mock_chunked, \
+         patch.object(client, "_diarize_and_transcribe_single") as mock_single:
+
+        mock_dur.return_value = 120.0
+        mock_single.return_value = {
+            "segments": [],
+            "speakers": [],
+            "transcripts": [],
+        }
+
+        client.diarize_and_transcribe(
+            audio_path=TEST_AUDIO_1,
+            verbose=False,
+            use_chunking=None,
+            max_single_request_duration=300.0,
+        )
+
+        mock_chunked.assert_not_called()
+        mock_single.assert_called_once()
+
+
+def test_chunked_transcription_adjusts_timestamps(client):
+    # Mock split_audio_into_chunks to return two chunks
+    chunk1_path = TEST_AUDIO_1
+    chunk2_path = TEST_AUDIO_1  # reusing same file; in real usage different
+
+    chunks = [
+        {"path": chunk1_path, "start": 0.0, "end": 10.0},
+        {"path": chunk2_path, "start": 10.0, "end": 20.0},
+    ]
+
+    with patch("scraibe.localai_client.split_audio_into_chunks") as mock_split, \
+         patch.object(client, "_diarize_and_transcribe_single") as mock_single, \
+         patch("os.remove"):
+
+        mock_split.return_value = chunks
+
+        # First chunk: segments 0–4
+        # Second chunk: segments 0–4 (local times)
+        def side_effect(audio_path, **kw):
+            if audio_path == chunk1_path:
+                segs = make_fake_segments(start=0.0, count=2)
+            else:
+                segs = make_fake_segments(start=0.0, count=2)
+            return client._parse_diarization_response(fake_localai_response(segs))
+
+        mock_single.side_effect = side_effect
+
+        result = client._diarize_and_transcribe_chunked(
+            audio_path=TEST_AUDIO_1,
+            verbose=False,
+            return_raw=False,
+            chunk_duration=10.0,
+            chunk_overlap=2.0,
+        )
+
+        # Check we got 4 segments total
+        assert len(result["segments"]) == 4
+
+        # First two segments should be in [0, 4]
+        assert result["segments"][0][0] == 0.0
+        assert result["segments"][1][0] == 2.0
+
+        # Next two segments should be shifted by 10
+        assert result["segments"][2][0] == 10.0
+        assert result["segments"][3][0] == 12.0
+
+
+@pytest.mark.integration
+def test_integration_chunked_transcription_with_localai():
+    """
+    Integration test: run chunked transcription against a live LocalAI instance.
+    Only runs if LOCALAI_API_URL is set and an audio file is provided.
+    This test is skipped by default unless run with:
+        pytest -m integration
+    """
+    api_url = os.getenv("LOCALAI_API_URL")
+    if not api_url:
+        pytest.skip("LOCALAI_API_URL not set; skipping integration test")
+
+    # Use one of the bundled test audio files
+    audio_path = TEST_AUDIO_1
+    if not os.path.exists(audio_path):
+        pytest.skip(f"Test audio not found: {audio_path}")
+
+    # Force chunking with a very small max_single_request_duration
+    # Use environment-configured model or a sensible default
+    model = os.getenv("LOCALAI_MODEL") or "vibevoice-cpp-asr"
+
+    client = LocalAIClient(api_url=api_url, model=model)
+    try:
+        result = client.diarize_and_transcribe(
+            audio_path=audio_path,
+            verbose=True,
+            return_raw=True,
+            use_chunking=True,
+            chunk_duration=3.0,
+            chunk_overlap=0.5,
+            max_single_request_duration=1.0,
+        )
+
+        assert "segments" in result
+        assert len(result["segments"]) > 0
+
+        # Basic sanity: segments are time-ordered
+        for i in range(1, len(result["segments"])):
+            prev_end = result["segments"][i - 1][1]
+            curr_start = result["segments"][i][0]
+            assert curr_start >= result["segments"][i - 1][0]
+
+        # If raw_result indicates chunked, ensure structure is sensible
+        raw = result.get("raw_result")
+        if raw and raw.get("chunked"):
+            assert "chunks" in raw
+            assert len(raw["chunks"]) > 1
+
+    finally:
+        client.close()