Stream the waveform compute so large uploads no longer buffer the whole file (Wave 2 OOM)

DeepDrftContent/Processors/ILoudnessAlgorithm.cs

@@ -20,4 +20,46 @@ public interface ILoudnessAlgorithm
     /// is 1. All zeros when the signal is silent (peak is 0) or no samples are present.
     /// </returns>
     double[] Compute(ReadOnlySpan<byte> pcmData, int channels, int sampleRate, int bitsPerSample, int bucketCount);
+
+    /// <summary>
+    /// Creates a stateful accumulator that reduces the same loudness profile from PCM fed in bounded
+    /// chunks rather than from one contiguous buffer. The streaming waveform path uses this so a long
+    /// track's PCM is never materialized whole in a managed <c>byte[]</c>. The accumulator's output is
+    /// byte-identical to <see cref="Compute"/> for the same total PCM, because <see cref="Compute"/> is
+    /// itself defined in terms of one — the single source of truth for the loudness reduction.
+    /// </summary>
+    /// <param name="pcmByteLength">
+    /// Total length of the PCM data region in bytes. Required up front because the bucket each frame
+    /// lands in is derived from the frame's position relative to the total frame count.
+    /// </param>
+    /// <param name="channels">Number of interleaved channels; averaged to mono per frame.</param>
+    /// <param name="sampleRate">Samples per second (used for the envelope-smoothing time base).</param>
+    /// <param name="bitsPerSample">Bit depth (8 unsigned, 16/24/32 signed) used to decode samples.</param>
+    /// <param name="bucketCount">Number of equal time slices to reduce the signal to.</param>
+    ILoudnessAccumulator CreateAccumulator(
+        long pcmByteLength, int channels, int sampleRate, int bitsPerSample, int bucketCount);
+}
+
+/// <summary>
+/// Stateful, single-pass reducer for one loudness profile. Frames are fed via <see cref="Add"/> in
+/// arbitrary (non-frame-aligned) chunks — a partial frame straddling a chunk boundary is carried
+/// internally — and <see cref="Finish"/> emits the peak-normalized <c>double[bucketCount]</c>. Not
+/// thread-safe; feed one stream sequentially. Reusable across the same stream's chunks only, not
+/// across streams.
+/// </summary>
+public interface ILoudnessAccumulator
+{
+    /// <summary>
+    /// Feeds the next run of PCM bytes (interleaved, little-endian). Need not be frame-aligned; bytes
+    /// that do not complete a frame are retained until the next call. Bytes past the total frame count
+    /// declared at construction are ignored, matching the whole-buffer path's trailing-partial-frame drop.
+    /// </summary>
+    void Add(ReadOnlySpan<byte> pcmChunk);
+
+    /// <summary>
+    /// Finalizes and returns the peak-normalized loudness profile (<c>double[bucketCount]</c>, each in
+    /// [0, 1]). All zeros for silence or a degenerate (no-frame) input. Call once, after the last
+    /// <see cref="Add"/>.
+    /// </summary>
+    double[] Finish();
 }