Add server-side waveform loudness profiling on track upload

ILoudnessAlgorithm strategy (RmsLoudnessAlgorithm first impl), WaveformProfileService
stores quantized byte[] sidecar in new MediaFileVault (profiles vault), wired into
UnifiedTrackService.UploadAsync; failure is logged and swallowed. WaveformProfileDto
and WaveformProfileOptions in shared projects.

DeepDrftContent/Constants/VaultConstants.cs

@@ -9,4 +9,9 @@ public static class VaultConstants
     /// Vault name for storing audio tracks
     /// </summary>
     public const string Tracks = "tracks";
+
+    /// <summary>
+    /// Vault name for storing waveform loudness profile sidecars, keyed by track EntryKey.
+    /// </summary>
+    public const string WaveformProfiles = "waveform-profiles";
 }

DeepDrftContent/DeepDrftContent.csproj

@@ -12,6 +12,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="10.0.0" />
+    <PackageReference Include="Microsoft.Extensions.Options" Version="10.0.0" />
   </ItemGroup>
 
   <ItemGroup>

DeepDrftContent/FileDatabase/Services/MediaVault.cs

@@ -219,6 +219,32 @@ public class AudioVault : MediaVault
     }
 }
 
+/// <summary>
+/// Concrete vault for plain <see cref="MediaBinary"/> entries (vault type
+/// <see cref="MediaVaultType.Media"/>) — bytes plus an extension, no audio/image-specific
+/// metadata. Used for sidecar artifacts such as waveform loudness profiles. The base
+/// <see cref="MediaVault"/> already handles Media-typed storage via the registry; this only
+/// provides the concrete factory the Image and Audio vaults also provide.
+/// </summary>
+public class MediaFileVault : MediaVault
+{
+    private MediaFileVault(string rootPath, VaultIndex index, IndexFactoryService? factoryService = null)
+        : base(rootPath, index, factoryService) { }
+
+    public static async Task<MediaFileVault?> FromAsync(string rootPath, IndexFactoryService? factoryService = null)
+    {
+        var factory = factoryService ?? new IndexFactoryService();
+        var index = await factory.LoadOrCreateVaultIndexAsync(rootPath, MediaVaultType.Media);
+
+        if (index != null)
+        {
+            return new MediaFileVault(rootPath, (VaultIndex)index, factory);
+        }
+
+        return null;
+    }
+}
+
 /// <summary>
 /// An open read-only stream over a vault entry plus the extension needed to
 /// resolve its MIME type. Caller owns the stream and must dispose it.

DeepDrftContent/FileDatabase/Services/MediaVaultFactory.cs

@@ -11,6 +11,7 @@ public static class MediaVaultFactory
     {
         return mediaType switch
         {
+            MediaVaultType.Media => await MediaFileVault.FromAsync(rootPath, factoryService),
             MediaVaultType.Image => await ImageVault.FromAsync(rootPath, factoryService),
             MediaVaultType.Audio => await AudioVault.FromAsync(rootPath, factoryService),
             _ => null

DeepDrftContent/FileDatabase/Services/SimpleMediaTypeRegistry.cs

@@ -31,7 +31,8 @@ public class SimpleMediaTypeRegistry : IMediaTypeRegistry
             dto => MediaBinary.From(dto),
             binary => new MediaBinaryDto(binary),
             (key, ext, _) => new MetaData(key, ext),
-            (binary, meta) => new MediaBinaryParams(binary.Buffer, binary.Size, meta.Extension));
+            (binary, meta) => new MediaBinaryParams(binary.Buffer, binary.Size, meta.Extension),
+            async path => await MediaFileVault.FromAsync(path));
 
         RegisterType<ImageBinary, ImageBinaryParams, ImageBinaryDto, ImageMetaData>(
             MediaVaultType.Image,

DeepDrftContent/Processors/AudioProcessor.cs

@@ -45,6 +45,55 @@ public class AudioProcessor
         }
     }
 
+    /// <summary>
+    /// Extracts the raw PCM data region and format parameters from a WAV buffer, reusing the
+    /// same chunk-walk and validation as metadata extraction. Returns null if the buffer is not
+    /// a valid PCM WAV (callers treat a null as "no profile computable" and continue) — unlike
+    /// <see cref="ExtractWavMetadata"/>, this does NOT fall back to synthetic defaults, because a
+    /// loudness profile over fabricated silence would be misleading.
+    /// </summary>
+    public PcmData? TryExtractPcm(ReadOnlySpan<byte> buffer)
+    {
+        // Copy the span to an array so the existing array-based parsers can be reused. The PCM
+        // slice returned is a view over this array (no second copy of the data region).
+        var bytes = buffer.ToArray();
+
+        var validation = ValidateWavStructure(bytes);
+        if (!validation.IsValid)
+        {
+            return null;
+        }
+
+        WavMetadata metadata;
+        try
+        {
+            metadata = ParseWavMetadata(bytes, validation);
+            ValidateAudioParameters(metadata);
+        }
+        catch
+        {
+            return null;
+        }
+
+        // Data bytes begin 8 past the "data" chunk id (4 id + 4 size). Clamp the declared size to
+        // what is actually present — some encoders write a size that overshoots the file.
+        var dataStart = validation.DataChunkPos + 8;
+        if (dataStart > bytes.Length)
+        {
+            return null;
+        }
+
+        var available = bytes.Length - dataStart;
+        var dataLength = Math.Min(metadata.DataSize, available);
+        if (dataLength <= 0)
+        {
+            return null;
+        }
+
+        var pcm = new ReadOnlyMemory<byte>(bytes, dataStart, dataLength);
+        return new PcmData(pcm, metadata.Channels, metadata.SampleRate, metadata.BitsPerSample);
+    }
+
     /// <summary>
     /// Extracts metadata from WAV file buffer with comprehensive validation
     /// </summary>
@@ -268,4 +317,18 @@ public class AudioProcessor
         public int FmtChunkPos { get; set; }
         public int DataChunkPos { get; set; }
     }
-}
+}
+
+/// <summary>
+/// The raw PCM sample region of a WAV plus the format parameters needed to interpret it.
+/// <see cref="Pcm"/> is a view over the decoded buffer — the data chunk only, header excluded.
+/// </summary>
+/// <param name="Pcm">The PCM sample bytes (interleaved by channel, little-endian).</param>
+/// <param name="Channels">Number of interleaved channels.</param>
+/// <param name="SampleRate">Samples per second.</param>
+/// <param name="BitsPerSample">Bit depth per sample (8, 16, 24, or 32).</param>
+public readonly record struct PcmData(
+    ReadOnlyMemory<byte> Pcm,
+    int Channels,
+    int SampleRate,
+    int BitsPerSample);

DeepDrftContent/Processors/ILoudnessAlgorithm.cs

@@ -0,0 +1,23 @@
+namespace DeepDrftContent.Processors;
+
+/// <summary>
+/// Strategy for reducing a stream of PCM samples to a fixed-length, peak-normalized loudness
+/// envelope. Swappable so the loudness measure (RMS today, LUFS later) can change without
+/// touching <c>WaveformProfileService</c>, the stored wire format, or the frontend renderer.
+/// </summary>
+public interface ILoudnessAlgorithm
+{
+    /// <summary>
+    /// Computes a peak-normalized loudness profile from raw interleaved PCM.
+    /// </summary>
+    /// <param name="pcmData">Interleaved, little-endian PCM sample bytes (the WAV data chunk).</param>
+    /// <param name="channels">Number of interleaved channels; averaged to mono per sample.</param>
+    /// <param name="sampleRate">Samples per second (unused by RMS but part of the contract for measures that need it).</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>
+    /// <returns>
+    /// A <c>double[bucketCount]</c>, each value in [0, 1], peak-normalized so the loudest bucket
+    /// 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);
+}

DeepDrftContent/Processors/RmsLoudnessAlgorithm.cs

@@ -0,0 +1,138 @@
+namespace DeepDrftContent.Processors;
+
+/// <summary>
+/// Loudness via root-mean-square amplitude per time bucket. Decodes signed PCM (8-bit unsigned,
+/// 16/24/32-bit signed little-endian), averages channels to mono, partitions the frames into
+/// equal time slices, takes the RMS of each slice, then peak-normalizes so the loudest bucket is 1.
+/// No external audio dependency — operates directly on the WAV data-chunk bytes.
+/// </summary>
+public class RmsLoudnessAlgorithm : ILoudnessAlgorithm
+{
+    public double[] Compute(ReadOnlySpan<byte> pcmData, int channels, int sampleRate, int bitsPerSample, int bucketCount)
+    {
+        if (bucketCount <= 0)
+        {
+            throw new ArgumentOutOfRangeException(nameof(bucketCount), "Bucket count must be positive.");
+        }
+
+        var result = new double[bucketCount];
+
+        if (channels <= 0)
+        {
+            return result;
+        }
+
+        var bytesPerSample = bitsPerSample / 8;
+        if (bytesPerSample <= 0)
+        {
+            return result;
+        }
+
+        var bytesPerFrame = bytesPerSample * channels;
+        var frameCount = pcmData.Length / bytesPerFrame;
+        if (frameCount == 0)
+        {
+            return result;
+        }
+
+        // Sum of squared mono amplitudes and the frame count, per bucket. A frame's bucket is
+        // determined by its position in the timeline so buckets are equal-duration slices.
+        var sumSquares = new double[bucketCount];
+        var counts = new long[bucketCount];
+
+        for (var frame = 0; frame < frameCount; frame++)
+        {
+            var frameStart = frame * bytesPerFrame;
+
+            double channelSum = 0;
+            for (var ch = 0; ch < channels; ch++)
+            {
+                var sampleStart = frameStart + ch * bytesPerSample;
+                channelSum += ReadSampleNormalized(pcmData, sampleStart, bitsPerSample);
+            }
+
+            var mono = channelSum / channels;
+
+            // long math avoids overflow on large files before the divide back into bucket index.
+            var bucket = (int)((long)frame * bucketCount / frameCount);
+            if (bucket >= bucketCount)
+            {
+                bucket = bucketCount - 1;
+            }
+
+            sumSquares[bucket] += mono * mono;
+            counts[bucket]++;
+        }
+
+        var peak = 0.0;
+        for (var i = 0; i < bucketCount; i++)
+        {
+            if (counts[i] > 0)
+            {
+                result[i] = Math.Sqrt(sumSquares[i] / counts[i]);
+                if (result[i] > peak)
+                {
+                    peak = result[i];
+                }
+            }
+        }
+
+        if (peak <= 0)
+        {
+            // Silence — return all zeros (Array is already zero-initialized).
+            Array.Clear(result);
+            return result;
+        }
+
+        for (var i = 0; i < bucketCount; i++)
+        {
+            result[i] /= peak;
+        }
+
+        return result;
+    }
+
+    /// <summary>
+    /// Decodes one PCM sample at <paramref name="offset"/> to a normalized amplitude in [-1, 1].
+    /// 8-bit is unsigned (0..255, centered at 128); 16/24/32-bit are signed little-endian.
+    /// </summary>
+    private static double ReadSampleNormalized(ReadOnlySpan<byte> data, int offset, int bitsPerSample)
+    {
+        switch (bitsPerSample)
+        {
+            case 8:
+                // Unsigned, midpoint 128.
+                return (data[offset] - 128) / 128.0;
+
+            case 16:
+            {
+                short sample = (short)(data[offset] | (data[offset + 1] << 8));
+                return sample / 32768.0;
+            }
+
+            case 24:
+            {
+                // Sign-extend the 24-bit little-endian value into an int.
+                int raw = data[offset] | (data[offset + 1] << 8) | (data[offset + 2] << 16);
+                if ((raw & 0x800000) != 0)
+                {
+                    raw |= unchecked((int)0xFF000000);
+                }
+                return raw / 8388608.0;
+            }
+
+            case 32:
+            {
+                int sample = data[offset]
+                             | (data[offset + 1] << 8)
+                             | (data[offset + 2] << 16)
+                             | (data[offset + 3] << 24);
+                return sample / 2147483648.0;
+            }
+
+            default:
+                throw new ArgumentOutOfRangeException(
+                    nameof(bitsPerSample), bitsPerSample, "Unsupported PCM bit depth.");
+        }
+    }
+}

DeepDrftContent/Processors/WaveformProfileOptions.cs

@@ -0,0 +1,11 @@
+namespace DeepDrftContent.Processors;
+
+/// <summary>
+/// Configuration for waveform loudness profiling. <see cref="BucketCount"/> is the stored
+/// resolution — the number of loudness buckets computed and persisted per track, which is also
+/// the bar count the frontend WaveformSeeker renders.
+/// </summary>
+public class WaveformProfileOptions
+{
+    public int BucketCount { get; set; } = 512;
+}

DeepDrftContent/Processors/WaveformProfileService.cs

@@ -0,0 +1,123 @@
+using DeepDrftContent.Constants;
+using DeepDrftContent.FileDatabase.Models;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+using FileDb = DeepDrftContent.FileDatabase.Services.FileDatabase;
+
+namespace DeepDrftContent.Processors;
+
+/// <summary>
+/// Computes a track's waveform loudness profile from its WAV bytes and persists it as a sidecar
+/// in the <see cref="VaultConstants.WaveformProfiles"/> vault, keyed by the track's EntryKey.
+/// The profile is the upload-time, off-the-playback-path representation the frontend fetches to
+/// render the WaveformSeeker. The loudness measure is injected (<see cref="ILoudnessAlgorithm"/>)
+/// so it can be swapped without changing storage or the wire format.
+/// </summary>
+public class WaveformProfileService
+{
+    private const string ProfileExtension = ".wfp";
+
+    private readonly FileDb _fileDatabase;
+    private readonly AudioProcessor _audioProcessor;
+    private readonly ILoudnessAlgorithm _loudnessAlgorithm;
+    private readonly WaveformProfileOptions _options;
+    private readonly ILogger<WaveformProfileService> _logger;
+
+    public WaveformProfileService(
+        FileDb fileDatabase,
+        AudioProcessor audioProcessor,
+        ILoudnessAlgorithm loudnessAlgorithm,
+        IOptions<WaveformProfileOptions> options,
+        ILogger<WaveformProfileService> logger)
+    {
+        _fileDatabase = fileDatabase;
+        _audioProcessor = audioProcessor;
+        _loudnessAlgorithm = loudnessAlgorithm;
+        _options = options.Value;
+        _logger = logger;
+    }
+
+    /// <summary>
+    /// Computes the loudness profile from <paramref name="wavBytes"/> and stores it under
+    /// <paramref name="entryKey"/>. Returns false (and logs) on any failure — a missing profile
+    /// is handled gracefully downstream, so callers on the upload path log-and-continue rather
+    /// than failing the upload. Does not throw for expected failure modes.
+    /// </summary>
+    public async Task<bool> ComputeAndStoreAsync(ReadOnlyMemory<byte> wavBytes, string entryKey)
+    {
+        try
+        {
+            var pcm = _audioProcessor.TryExtractPcm(wavBytes.Span);
+            if (pcm is null)
+            {
+                _logger.LogWarning(
+                    "Waveform profile not computed for {EntryKey}: WAV PCM could not be extracted.",
+                    entryKey);
+                return false;
+            }
+
+            var value = pcm.Value;
+            var profile = _loudnessAlgorithm.Compute(
+                value.Pcm.Span,
+                value.Channels,
+                value.SampleRate,
+                value.BitsPerSample,
+                _options.BucketCount);
+
+            var quantized = Quantize(profile);
+
+            await EnsureVaultAsync();
+
+            var binary = new MediaBinary(new MediaBinaryParams(quantized, quantized.Length, ProfileExtension));
+            var stored = await _fileDatabase.RegisterResourceAsync(
+                VaultConstants.WaveformProfiles, entryKey, binary);
+
+            if (!stored)
+            {
+                _logger.LogWarning("Waveform profile vault write failed for {EntryKey}.", entryKey);
+                return false;
+            }
+
+            return true;
+        }
+        catch (Exception ex) when (ex is not OperationCanceledException)
+        {
+            _logger.LogError(ex, "Waveform profile computation failed for {EntryKey}.", entryKey);
+            return false;
+        }
+    }
+
+    /// <summary>
+    /// Returns the stored quantized profile bytes for a track, or null if no profile is stored
+    /// (existing tracks predate profiling, and computation may have failed). Each byte is a
+    /// peak-normalized loudness value in [0, 255].
+    /// </summary>
+    public async Task<byte[]?> GetProfileAsync(string entryKey)
+    {
+        var binary = await _fileDatabase.LoadResourceAsync<MediaBinary>(
+            VaultConstants.WaveformProfiles, entryKey);
+        return binary?.Buffer;
+    }
+
+    /// <summary>
+    /// Maps each [0, 1] bucket to a [0, 255] byte. 1.0 maps to 255; the multiply-by-255 with a
+    /// truncating cast keeps every in-range value within a byte without a clamp branch.
+    /// </summary>
+    private static byte[] Quantize(double[] profile)
+    {
+        var bytes = new byte[profile.Length];
+        for (var i = 0; i < profile.Length; i++)
+        {
+            bytes[i] = (byte)(profile[i] * 255);
+        }
+        return bytes;
+    }
+
+    private async Task EnsureVaultAsync()
+    {
+        if (!_fileDatabase.HasVault(VaultConstants.WaveformProfiles))
+        {
+            await _fileDatabase.CreateVaultAsync(VaultConstants.WaveformProfiles, MediaVaultType.Media);
+        }
+    }
+}