fix(audio): support WAVE_FORMAT_EXTENSIBLE PCM WAVs, normalizing them to standard PCM on upload

DeepDrftContent/Processors/AudioProcessor.cs

@@ -28,10 +28,15 @@ public class AudioProcessor
         {
             var buffer = await File.ReadAllBytesAsync(filePath);
             var wavInfo = ExtractWavMetadata(buffer);
-            
+
+            // EXTENSIBLE-PCM is byte-compatible with standard PCM but carries a 40+ byte fmt chunk
+            // the streaming pipeline never expects. Normalize to a plain 44-byte PCM WAV at storage
+            // time so the vault only ever holds standard PCM and the client decode path stays unchanged.
+            var storedBuffer = wavInfo.IsExtensible ? NormalizeToStandardPcm(buffer, wavInfo) : buffer;
+
             var parameters = new AudioBinaryParams(
-                Buffer: buffer,
-                Size: buffer.Length,
+                Buffer: storedBuffer,
+                Size: storedBuffer.Length,
                 Extension: ".wav",
                 Duration: wavInfo.Duration,
                 Bitrate: wavInfo.Bitrate
@@ -156,9 +161,30 @@ public class AudioProcessor
             return new WavValidationResult { IsValid = false, ErrorMessage = "fmt chunk too small" };
         }
 
-        // Validate audio format (PCM only)
+        // Validate audio format. Standard PCM (1) is accepted directly. WAVE_FORMAT_EXTENSIBLE
+        // (0xFFFE) is accepted only when its SubFormat GUID indicates PCM — the raw sample data is
+        // then byte-identical to standard PCM and we normalize it downstream.
         var audioFormat = BitConverter.ToUInt16(buffer, fmtChunkPos + 8);
-        if (audioFormat != 1)
+        var isExtensible = false;
+        if (audioFormat == 0xFFFE)
+        {
+            // EXTENSIBLE requires the full extension: 16 base + 2 cbSize + 22 extension = 40 bytes.
+            if (fmtChunkSize < 40)
+            {
+                return new WavValidationResult { IsValid = false, ErrorMessage = "Invalid data: EXTENSIBLE fmt chunk too small" };
+            }
+
+            // SubFormat GUID begins 24 bytes into the fmt chunk data (fmtChunkPos + 8 + 24). Its
+            // first two bytes are the little-endian format tag; 0x0001 == WAVE_FORMAT_PCM.
+            var subFormatPos = fmtChunkPos + 8 + 24;
+            if (buffer[subFormatPos] != 0x01 || buffer[subFormatPos + 1] != 0x00)
+            {
+                return new WavValidationResult { IsValid = false, ErrorMessage = "Invalid data: EXTENSIBLE SubFormat is not PCM" };
+            }
+
+            isExtensible = true;
+        }
+        else if (audioFormat != 1)
         {
             return new WavValidationResult { IsValid = false, ErrorMessage = "Only PCM format supported" };
         }
@@ -170,11 +196,12 @@ public class AudioProcessor
             return new WavValidationResult { IsValid = false, ErrorMessage = "Missing data chunk" };
         }
 
-        return new WavValidationResult 
-        { 
-            IsValid = true, 
+        return new WavValidationResult
+        {
+            IsValid = true,
             FmtChunkPos = fmtChunkPos,
-            DataChunkPos = dataChunkPos
+            DataChunkPos = dataChunkPos,
+            IsExtensible = isExtensible
         };
     }
     
@@ -190,6 +217,14 @@ public class AudioProcessor
         var bitsPerSample = BitConverter.ToUInt16(buffer, validation.FmtChunkPos + 22);
         var dataSize = BitConverter.ToUInt32(buffer, validation.DataChunkPos + 4);
 
+        // For EXTENSIBLE the offset-22 field is the container width; the true sample depth lives in
+        // wValidBitsPerSample (fmtChunkPos + 8 + 18). They usually match (Bandcamp 24-bit = 24/24)
+        // but the valid bits are authoritative for the normalized header and metadata.
+        if (validation.IsExtensible)
+        {
+            bitsPerSample = BitConverter.ToUInt16(buffer, validation.FmtChunkPos + 8 + 18);
+        }
+
         var duration = byteRate > 0 ? (double)dataSize / byteRate : 0.0;
         var bitrate = (int)((sampleRate * channels * bitsPerSample) / 1000);
 
@@ -201,7 +236,9 @@ public class AudioProcessor
             Channels = channels,
             BitsPerSample = bitsPerSample,
             BlockAlign = blockAlign,
-            DataSize = (int)dataSize
+            DataSize = (int)dataSize,
+            DataChunkPos = validation.DataChunkPos,
+            IsExtensible = validation.IsExtensible
         };
     }
     
@@ -235,6 +272,48 @@ public class AudioProcessor
         }
     }
     
+    /// <summary>
+    /// Rebuilds an EXTENSIBLE-PCM WAV as a canonical 44-byte-header standard PCM WAV (audioFormat = 1).
+    /// The sample bytes are copied verbatim — EXTENSIBLE-PCM data is byte-identical to standard PCM —
+    /// only the header is replaced, so the vault stores a format the streaming pipeline already handles.
+    /// </summary>
+    private byte[] NormalizeToStandardPcm(byte[] buffer, WavMetadata metadata)
+    {
+        // Clamp the declared data size to what is actually present; some encoders overshoot.
+        var dataStart = metadata.DataChunkPos + 8;
+        var available = buffer.Length - dataStart;
+        var dataSize = Math.Min(metadata.DataSize, available);
+
+        const int headerSize = 44;
+        var result = new byte[headerSize + dataSize];
+
+        var blockAlign = (ushort)(metadata.Channels * (metadata.BitsPerSample / 8));
+        var byteRate = (uint)(metadata.SampleRate * blockAlign);
+
+        // RIFF header
+        System.Text.Encoding.ASCII.GetBytes("RIFF").CopyTo(result, 0);
+        BitConverter.GetBytes((uint)(36 + dataSize)).CopyTo(result, 4);
+        System.Text.Encoding.ASCII.GetBytes("WAVE").CopyTo(result, 8);
+
+        // fmt chunk (standard 16-byte PCM)
+        System.Text.Encoding.ASCII.GetBytes("fmt ").CopyTo(result, 12);
+        BitConverter.GetBytes((uint)16).CopyTo(result, 16);
+        BitConverter.GetBytes((ushort)1).CopyTo(result, 20); // audioFormat = PCM
+        BitConverter.GetBytes((ushort)metadata.Channels).CopyTo(result, 22);
+        BitConverter.GetBytes((uint)metadata.SampleRate).CopyTo(result, 24);
+        BitConverter.GetBytes(byteRate).CopyTo(result, 28);
+        BitConverter.GetBytes(blockAlign).CopyTo(result, 32);
+        BitConverter.GetBytes((ushort)metadata.BitsPerSample).CopyTo(result, 34);
+
+        // data chunk
+        System.Text.Encoding.ASCII.GetBytes("data").CopyTo(result, 36);
+        BitConverter.GetBytes((uint)dataSize).CopyTo(result, 40);
+
+        Array.Copy(buffer, dataStart, result, headerSize, dataSize);
+
+        return result;
+    }
+
     /// <summary>
     /// Returns default WAV metadata for fallback scenarios
     /// </summary>
@@ -305,6 +384,8 @@ public class AudioProcessor
         public int BitsPerSample { get; set; }
         public int BlockAlign { get; set; }
         public int DataSize { get; set; }
+        public int DataChunkPos { get; set; }
+        public bool IsExtensible { get; set; }
     }
     
     /// <summary>
@@ -316,6 +397,7 @@ public class AudioProcessor
         public string ErrorMessage { get; set; } = string.Empty;
         public int FmtChunkPos { get; set; }
         public int DataChunkPos { get; set; }
+        public bool IsExtensible { get; set; }
     }
 }