[MM] Allow audio chunking for offline LLM (#34628)

Signed-off-by: NickLucche <nlucches@redhat.com>

vllm/multimodal/audio.py

@@ -216,3 +216,121 @@ class AudioResampler:
                 f"Invalid resampling method: {self.method}. "
                 "Supported methods are 'librosa' and 'scipy'."
             )
+
+
+# ============================================================
+# Audio Chunking / Splitting
+# ============================================================
+
+
+def split_audio(
+    audio_data: np.ndarray,
+    sample_rate: int,
+    max_clip_duration_s: float,
+    overlap_duration_s: float,
+    min_energy_window_size: int,
+) -> list[np.ndarray]:
+    """Split audio into chunks with intelligent split points.
+
+    Splits long audio into smaller chunks at low-energy regions to minimize
+    cutting through speech. Uses overlapping windows to find quiet moments
+    for splitting.
+
+    Args:
+        audio_data: Audio array to split. Can be 1D (mono) or multi-dimensional.
+                   Splits along the last dimension (time axis).
+        sample_rate: Sample rate of the audio in Hz.
+        max_clip_duration_s: Maximum duration of each chunk in seconds.
+        overlap_duration_s: Overlap duration in seconds between consecutive chunks.
+                           Used to search for optimal split points.
+        min_energy_window_size: Window size in samples for finding low-energy regions.
+
+    Returns:
+        List of audio chunks. Each chunk is a numpy array with the same shape
+        as the input except for the last (time) dimension.
+
+    Example:
+        >>> audio = np.random.randn(1040000)  # 65 seconds at 16kHz
+        >>> chunks = split_audio(
+        ...     audio_data=audio,
+        ...     sample_rate=16000,
+        ...     max_clip_duration_s=30.0,
+        ...     overlap_duration_s=1.0,
+        ...     min_energy_window_size=1600,
+        ... )
+        >>> len(chunks)
+        3
+    """
+    chunk_size = int(sample_rate * max_clip_duration_s)
+    overlap_size = int(sample_rate * overlap_duration_s)
+    chunks = []
+    i = 0
+
+    while i < audio_data.shape[-1]:
+        if i + chunk_size >= audio_data.shape[-1]:
+            # Handle last chunk - take everything remaining
+            chunks.append(audio_data[..., i:])
+            break
+
+        # Find the best split point in the overlap region
+        search_start = i + chunk_size - overlap_size
+        search_end = min(i + chunk_size, audio_data.shape[-1])
+        split_point = find_split_point(
+            audio_data, search_start, search_end, min_energy_window_size
+        )
+
+        # Extract chunk up to the split point
+        chunks.append(audio_data[..., i:split_point])
+        i = split_point
+
+    return chunks
+
+
+def find_split_point(
+    wav: np.ndarray,
+    start_idx: int,
+    end_idx: int,
+    min_energy_window: int,
+) -> int:
+    """Find the best point to split audio by looking for silence or low amplitude.
+
+    Searches for the quietest region within a specified range by calculating
+    RMS energy in sliding windows.
+
+    Args:
+        wav: Audio array. Can be 1D or multi-dimensional.
+        start_idx: Start index of search region (inclusive).
+        end_idx: End index of search region (exclusive).
+        min_energy_window: Window size in samples for energy calculation.
+
+    Returns:
+        Index of the quietest point within the search region. This is the
+        recommended split point to minimize audio artifacts.
+
+    Example:
+        >>> audio = np.random.randn(32000)
+        >>> # Insert quiet region
+        >>> audio[16000:17600] = 0.01
+        >>> split_idx = find_split_point(
+        ...     wav=audio,
+        ...     start_idx=0,
+        ...     end_idx=32000,
+        ...     min_energy_window=1600,
+        ... )
+        >>> 16000 <= split_idx <= 17600
+        True
+    """
+    segment = wav[start_idx:end_idx]
+
+    # Calculate RMS energy in small windows
+    min_energy = math.inf
+    quietest_idx = 0
+
+    for i in range(0, len(segment) - min_energy_window, min_energy_window):
+        window = segment[i : i + min_energy_window]
+        energy = (window**2).mean() ** 0.5
+        if energy < min_energy:
+            quietest_idx = i + start_idx
+            min_energy = energy
+
+    return quietest_idx