feat(api): derive Mix waveform datum density from duration (~333 samples/sec, capped/floored) instead of fixed 2048 buckets

DeepDrftAPI/Services/UnifiedReleaseService.cs

@@ -17,10 +17,6 @@ namespace DeepDrftAPI.Services;
 /// </summary>
 public class UnifiedReleaseService
 {
-    // High-res bucket count for Mix waveforms — 4x the player-bar default (512), feeding the
-    // public-site MixWaveformVisualizer.
-    private const int MixWaveformBucketCount = 2048;
-
     /// <summary>Error message returned when the Mix release has no linked track.</summary>
     public const string MixHasNoTrackMessage = "Mix release has no track.";
 
@@ -104,9 +100,11 @@ public class UnifiedReleaseService
     }
 
     /// <summary>
-    /// Fetch the Mix's track audio from the vault, compute a high-res (2048-bucket) waveform datum,
-    /// store it in the MixWaveforms vault under the track's EntryKey, then point the release's Mix
-    /// satellite at that same key. The datum key equals the track's EntryKey — the Mix is single-track.
+    /// Fetch the Mix's track audio from the vault, compute a high-res waveform datum at a constant time
+    /// resolution (≈333 samples/sec derived from the track's duration; see
+    /// <see cref="MixWaveformResolution"/>), store it in the MixWaveforms vault under the track's
+    /// EntryKey, then point the release's Mix satellite at that same key. The datum key equals the
+    /// track's EntryKey — the Mix is single-track.
     /// </summary>
     public async Task<Result> TriggerMixWaveformAsync(long releaseId, CancellationToken ct)
     {
@@ -149,8 +147,11 @@ public class UnifiedReleaseService
             return Result.CreateFailResult(MixTrackNoAudioMessage);
         }
 
+        // Duration-derived, constant-time-resolution capture (≈333 samples/sec) so long mixes are not
+        // under-sampled by a fixed bucket count — see MixWaveformResolution / spec §F.
+        var bucketCount = MixWaveformResolution.BucketCountForDuration(audio.Duration);
         var computed = await _waveformProfileService.ComputeAndStoreAsync(
-            audio.Buffer, entryKey, MixWaveformBucketCount, VaultConstants.MixWaveforms);
+            audio.Buffer, entryKey, bucketCount, VaultConstants.MixWaveforms);
         if (!computed)
         {
             _logger.LogError("TriggerMixWaveform: waveform computation/storage failed for {EntryKey}", entryKey);