Separate class for ffprobe process. Removed FfmpegPipe class. Reader is lazy now.

AudioCore/Impl/FfmpegAudioReader.cs

@@ -1,27 +1,88 @@
-namespace AudioCore.Impl;
+using System.Diagnostics;
 
-public sealed class FfmpegAudioReader : IAudioReader
+namespace AudioCore.Impl;
+
+public sealed class FfmpegAudioReader : IAudioReader, IDisposable
 {
-    private readonly FfmpegPipe _pipe;
+    private readonly string _path;
 
-    public int SampleRate => _pipe.SampleRate;
+    // Lazy process wrapper
-    public int Channels => _pipe.Channels;
+    private Lazy<FfmpegProcess> _process;
-    public long TotalSamples => _pipe.TotalSamples;
+
+    // Remember last seek position
+    private long _pendingSeekSample = 0;
+
+    public int SampleRate { get; }
+    public int Channels { get; }
+    public long TotalSamples { get; }
+    public TimeSpan Duration { get; }
 
     public FfmpegAudioReader(string path)
     {
-        _pipe = new FfmpegPipe(path);
+        _path = path;
+
+        var probe = FfprobeProcess.ProbeAudio(path);
+
+        SampleRate = probe.SampleRate;
+        Channels = probe.Channels;
+        TotalSamples = probe.TotalSamples;
+        Duration = probe.Duration;
+
+        _process = CreateLazyProcess();
     }
 
+    private Lazy<FfmpegProcess> CreateLazyProcess() => new Lazy<FfmpegProcess>(() =>
+        {
+            var startSeconds = (double)_pendingSeekSample / SampleRate;
+
+            var cmd =
+                "-hide_banner -loglevel error " +
+                "-nostdin " +
+                $"-ss {startSeconds.ToString(System.Globalization.CultureInfo.InvariantCulture)} " +
+                $"-i \"{_path}\" " +
+                $"-f f32le -ac {Channels} -ar {SampleRate} pipe:1";
+
+            var p = new FfmpegProcess(
+                name: $"pipe:{_path}",
+                commandLine: cmd,
+                redirectOutput: true,
+                redirectInput: true);
+
+            p.StartProcess();
+            return p;
+        });
+
     public int Read(float[] buffer, int offset, int count)
-        => _pipe.Read(buffer, offset, count);
+    {
+        var proc = _process.Value; // starts process if not started
+        if (proc.Stdout is null)
+            return 0;
+
+        return proc.Read(buffer, offset, count);
+    }
 
     public void Seek(long sampleIndex)
-        => _pipe.Seek(sampleIndex);
+    {
+        _pendingSeekSample = sampleIndex;
+        DisposeProcessOnly();
+        _process = CreateLazyProcess(); // new lazy instance
+    }
 
     public void Reset()
-        => Seek(0);
+    {
+        Seek(0);
+    }
+
+    private void DisposeProcessOnly()
+    {
+        if (_process.IsValueCreated)
+        {
+            try { _process.Value.Dispose(); } catch { }
+        }
+    }
 
     public void Dispose()
-        => _pipe.Dispose();
+    {
+        DisposeProcessOnly();
+    }
 }

AudioCore/Impl/FfmpegPipe.cs

@@ -1,112 +0,0 @@
-using System.Diagnostics;
-
-namespace AudioCore.Impl;
-
-public sealed class FfmpegPipe : IDisposable
-{
-    private readonly string _path;
-    private Process? _proc;
-    private Stream? _stdout;
-
-    public int SampleRate { get; }
-    public int Channels { get; }
-    public long TotalSamples { get; }
-
-    public FfmpegPipe(string path, int sampleRate = 44100, int channels = 2)
-    {
-        _path = path;
-        SampleRate = sampleRate;
-        Channels = channels;
-
-        // Optional: probe duration
-        TotalSamples = ProbeTotalSamples(path, sampleRate);
-
-        StartProcess(0);
-    }
-
-    private void StartProcess(long startSample)
-    {
-        var startSeconds = (double)startSample / SampleRate;
-
-        var psi = new ProcessStartInfo
-        {
-            FileName = "ffmpeg",
-            Arguments =
-            $"-hide_banner -loglevel error " +
-            $"-nostdin " +                     // prevent console attach
-            $"-ss {startSeconds.ToString(System.Globalization.CultureInfo.InvariantCulture)} " +
-            $"-i \"{_path}\" " +
-            $"-f f32le -ac {Channels} -ar {SampleRate} pipe:1",
-
-            UseShellExecute        = false,
-            RedirectStandardOutput = true,
-            RedirectStandardError  = true,
-            RedirectStandardInput  = true,         // prevents console window
-            CreateNoWindow         = true,
-            WindowStyle            = ProcessWindowStyle.Hidden,
-            ErrorDialog            = false
-        };
-
-        _proc = Process.Start(psi);
-        _stdout = _proc!.StandardOutput.BaseStream;
-    }
-
-    public int Read(float[] buffer, int offset, int count)
-    {
-        var bytesNeeded = count * sizeof(float);
-        var tmp = new byte[bytesNeeded];
-
-        var readBytes = _stdout!.Read(tmp, 0, bytesNeeded);
-        if (readBytes <= 0)
-            return 0;
-
-        Buffer.BlockCopy(tmp, 0, buffer, offset * sizeof(float), readBytes);
-
-        return readBytes / sizeof(float);
-    }
-
-    public void Seek(long sampleIndex)
-    {
-        DisposeProcessOnly();
-        StartProcess(sampleIndex);
-    }
-
-    public void Reset() => Seek(0);
-
-    private static long ProbeTotalSamples(string path, int sampleRate)
-    {
-        var psi = new ProcessStartInfo
-        {
-            FileName               = "ffprobe",
-            Arguments              = $"-v error -show_entries format=duration -of csv=p=0 \"{path}\"",
-            RedirectStandardOutput = true,
-            CreateNoWindow         = true,
-            WindowStyle            = ProcessWindowStyle.Hidden,
-            UseShellExecute        = false
-        };
-
-        using var p = Process.Start(psi);
-        var s = p!.StandardOutput.ReadToEnd();
-        p.WaitForExit();
-
-        if (double.TryParse(s, System.Globalization.NumberStyles.Float,
-            System.Globalization.CultureInfo.InvariantCulture, out var seconds))
-        {
-            return (long)(seconds * sampleRate);
-        }
-
-        return 0;
-    }
-
-    private void DisposeProcessOnly()
-    {
-        try { _stdout?.Dispose(); } catch { }
-        try { if (_proc != null && !_proc.HasExited) _proc.Kill(); } catch { }
-        try { _proc?.Dispose(); } catch { }
-    }
-
-    public void Dispose()
-    {
-        DisposeProcessOnly();
-    }
-}

AudioCore/Impl/FfmpegProcess.cs

@@ -0,0 +1,104 @@
+using System.Diagnostics;
+using System.Text.Json;
+
+namespace AudioCore.Impl;
+
+public sealed class FfmpegProcess : IDisposable
+{
+    public Process? Proc  { get; private set; }
+    public Stream? Stdout { get; private set; }
+    public Stream? Stdin  { get; private set; }
+
+    private string _name;
+    private string _commandLine;
+    private bool   _redirectOutput;
+    private bool   _redirectInput;
+
+    public FfmpegProcess(string name, string commandLine, bool redirectOutput = true, bool redirectInput = true)
+    {
+        _name           = name;
+        _commandLine    = commandLine;
+        _redirectOutput = redirectOutput;
+        _redirectInput  = redirectInput;
+    }
+
+    public void StartProcess()
+    {
+        Debug.WriteLine($"{_name}: Starting ffmpeg process");
+
+        var psi = new ProcessStartInfo
+        {
+            FileName               = "ffmpeg",
+            Arguments              = _commandLine,
+            UseShellExecute        = false,
+            RedirectStandardOutput = _redirectOutput,
+            RedirectStandardError  = true,
+            RedirectStandardInput  = _redirectInput,
+            CreateNoWindow         = true,
+            WindowStyle            = ProcessWindowStyle.Hidden,
+            ErrorDialog            = false
+        };
+
+        Proc = Process.Start(psi) ?? throw new InvalidOperationException("Failed to start ffmpeg process");
+
+        if ( _redirectInput)
+            Stdin = Proc.StandardInput.BaseStream;
+        if (_redirectOutput)
+            Stdout = Proc.StandardOutput.BaseStream;
+
+        // Start draining stderr immediately
+        _ = Task.Run(() => DrainStderr(Proc));
+    }
+
+    private void DrainStderr(Process proc)
+    {
+        try
+        {
+            var reader = proc.StandardError;
+
+            // ffmpeg writes short lines, so ReadLine is fine
+            // If you want zero allocations, use ReadAsync into a rented buffer.
+            string? line;
+            while ((line = reader.ReadLine()) != null)
+            {
+                Debug.WriteLine($"{_name}: {line}");
+            }
+        }
+        catch
+        {
+            // ignore exceptions during stderr drain, as the process may have exited
+        }
+    }
+
+    public int Read(float[] buffer, int offset, int count)
+    {
+        var bytesNeeded = count * sizeof(float);
+        var tmp = new byte[bytesNeeded];
+
+        var readBytes = Stdout!.Read(tmp, 0, bytesNeeded);
+        if (readBytes <= 0)
+            return 0;
+
+        Buffer.BlockCopy(tmp, 0, buffer, offset * sizeof(float), readBytes);
+
+        return readBytes / sizeof(float);
+    }
+
+
+    private void DisposeProcessOnly()
+    {
+        if (Proc != null)
+            Debug.WriteLine($"{_name}: Disposing ffmpeg process");
+
+        try { Stdout?.Dispose(); Stdout = null;                 } catch { }
+        try { Stdin?.Dispose(); Stdin = null;                   } catch { }
+        try { Proc?.StandardError.BaseStream?.Dispose();        } catch { }
+        try { if (Proc != null && !Proc.HasExited) Proc.Kill(); } catch { }
+        try { Proc?.Dispose(); Proc = null;                     } catch { }
+    }
+
+    public void Dispose()
+    {
+        DisposeProcessOnly();
+    }
+}

AudioCore/Impl/FfprobeProcess.cs

@@ -0,0 +1,108 @@
+using System.Diagnostics;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace AudioCore.Impl;
+
+public class AudioProbe
+{
+    public int      SampleRate   { get; init; }
+    public int      Channels     { get; init; }
+    public long     TotalSamples { get; init; }
+    public TimeSpan Duration     { get; init; }
+}
+
+public static class FfprobeProcess
+{
+    private sealed class FfprobeJson
+    {
+        public FfprobeFormat? Format { get; set; }
+        public FfprobeStream[]? Streams { get; set; }
+    }
+
+    private sealed class FfprobeFormat
+    {
+        public string? Duration { get; set; }
+    }
+
+    private sealed class FfprobeStream
+    {
+        [JsonConverter(typeof(IntFlexibleConverter))]
+        public int Sample_Rate { get; set; }
+        [JsonConverter(typeof(IntFlexibleConverter))]
+        public int Channels { get; set; }
+    }
+
+    private sealed class IntFlexibleConverter : JsonConverter<int>
+    {
+        public override int Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            return reader.TokenType switch
+            {
+                JsonTokenType.Number => reader.GetInt32(),
+                JsonTokenType.String => int.Parse(reader.GetString()!, System.Globalization.CultureInfo.InvariantCulture),
+                _ => throw new JsonException($"Invalid token for int: {reader.TokenType}")
+            };
+        }
+
+        public override void Write(Utf8JsonWriter writer, int value, JsonSerializerOptions options)
+        {
+            writer.WriteNumberValue(value);
+        }
+    }
+
+    public static AudioProbe ProbeAudio(string path)
+    {
+        var psi = new ProcessStartInfo
+        {
+            FileName               = "ffprobe",
+            Arguments              =
+                "-v error " +
+                "-select_streams a:0 " +
+                "-show_entries format=duration " +
+                "-show_entries stream=sample_rate,channels " +
+                "-print_format json " +
+                $"\"{path}\"",
+            RedirectStandardOutput = true,
+            UseShellExecute        = false,
+            CreateNoWindow         = true,
+            WindowStyle            = ProcessWindowStyle.Hidden
+        };
+
+        using var p = Process.Start(psi) ?? throw new InvalidOperationException("ffprobe failed");
+        var json = p.StandardOutput.ReadToEnd();
+        p.WaitForExit();
+
+        var opts = new JsonSerializerOptions
+        {
+            PropertyNameCaseInsensitive = true
+        };
+
+        var probe = JsonSerializer.Deserialize<FfprobeJson>(json, opts)
+                    ?? throw new InvalidOperationException("Invalid ffprobe JSON");
+
+        if (probe.Format?.Duration is null)
+            throw new InvalidOperationException("ffprobe missing duration");
+
+        if (probe.Streams is null || probe.Streams.Length == 0)
+            throw new InvalidOperationException("ffprobe missing audio stream");
+
+        var stream = probe.Streams[0];
+
+        var durationSeconds = double.Parse(probe.Format.Duration,
+            System.Globalization.CultureInfo.InvariantCulture);
+
+        var sampleRate = stream.Sample_Rate;
+        var channels   = stream.Channels;
+
+        var totalSamples = (long)(durationSeconds * sampleRate);
+
+        return new AudioProbe
+        {
+            SampleRate = sampleRate,
+            Channels = channels,
+            Duration = TimeSpan.FromSeconds(durationSeconds),
+            TotalSamples = totalSamples
+        };
+    }
+}

AudioCore/Impl/Htdemucs6sSeparator.cs

@@ -9,9 +9,9 @@ public sealed class Htdemucs6sSeparator : IStemSeparator
     private const int _sampleRate        = 44100;
     private const int _channels          = 2;
     private const double _segmentSeconds = 7.8;
-    private const int _segmentSamples    = (int)(_sampleRate * _segmentSeconds); // 343,980
+    private const int _segmentSamples    = (int)(_sampleRate * _segmentSeconds);
-    private const int _overlap           = _segmentSamples / 4;                  // 85,995
+    private const int _overlap           = _segmentSamples / 4;
-    private const int _stride            = _segmentSamples - _overlap;           // 257,985
+    private const int _stride            = _segmentSamples - _overlap;
 
     private static readonly string[] _stemNames = Enum.GetNames<StemType>();
 
@@ -26,14 +26,12 @@ public sealed class Htdemucs6sSeparator : IStemSeparator
         if (existingStems != null)
             return existingStems;
 
-        // 1. Load audio
         var mix = LoadStereoFloatWave(request.SourceFilePath, out var sr);
         if (sr != _sampleRate)
             throw new InvalidOperationException($"Input must be {_sampleRate} Hz");
 
         var totalSamples = mix.GetLength(1);
 
-        // 2. Prepare ONNX session 
         var opts = new SessionOptions();
         opts.AppendExecutionProvider_CPU();
         opts.GraphOptimizationLevel = GraphOptimizationLevel.ORT_ENABLE_ALL;
@@ -41,14 +39,12 @@ public sealed class Htdemucs6sSeparator : IStemSeparator
         var modelPath = Path.Combine(AppContext.BaseDirectory, "Data", "htdemucs_6s.onnx");
         using var session = new InferenceSession(modelPath, opts);
 
-        // 3. Prepare buffers
         var outStems = new float[_stemNames.Length, _channels, totalSamples];
         var weight   = new float[totalSamples];
         var window   = MakeWindow(_segmentSamples, _overlap);
 
         var nChunks = Math.Max(1, (totalSamples + _stride - 1) / _stride);
 
-        // 4. Sliding window inference
         for (var i = 0; i < nChunks; i++)
         {
             ct.ThrowIfCancellationRequested();
@@ -57,14 +53,10 @@ public sealed class Htdemucs6sSeparator : IStemSeparator
             var end   = Math.Min(start + _segmentSamples, totalSamples);
             var clen  = end - start;
 
-            // Extract chunk into [2, N]
             var chunk = new float[_channels, _segmentSamples];
             for (var ch = 0; ch < _channels; ch++)
-            {
                 Array.Copy(mix, ch * totalSamples + start, chunk, ch * _segmentSamples, clen);
-            }
 
-            // Build flat input buffer (1,2,N)
             var inputData = new float[_channels * _segmentSamples];
             for (var ch = 0; ch < _channels; ch++)
             {
@@ -73,42 +65,31 @@ public sealed class Htdemucs6sSeparator : IStemSeparator
                     inputData[baseIndex + s] = chunk[ch, s];
             }
 
-            // Create OrtValue for input
             using var inputOrtValue = OrtValue.CreateTensorValueFromMemory(
                 inputData,
-    new long[] { 1, _channels, _segmentSamples }
+                new long[] { 1, _channels, _segmentSamples });
-);
 
-            // Prepare output buffer (CPU)
             var outputData = new float[_stemNames.Length * _channels * _segmentSamples];
 
-            // Create OrtValue for output
             using var outputOrtValue = OrtValue.CreateTensorValueFromMemory(
                 outputData,
-    new long[] { 1, _stemNames.Length, _channels, _segmentSamples }
+                new long[] { 1, _stemNames.Length, _channels, _segmentSamples });
-);
 
-            // Bind using IOBinding
             using var io = session.CreateIoBinding();
             io.BindInput("mix", inputOrtValue);
             io.BindOutput("stems", outputOrtValue);
 
-            // Execute on GPU → output goes directly to CPU buffer
             session.RunWithBinding(new RunOptions(), io);
 
-            // Now outputData contains (1,6,2,N)
             var buf = outputData.AsSpan();
 
-            // Extract output tensor shape (1, 6, 2, N)
+            var stemCnt  = _stemNames.Length;
-            var stemCnt  = _stemNames.Length;   // 6
+            var chCnt    = _channels;
-            var chCnt    = _channels;           // 2
+            var length   = _segmentSamples;
-            var length   = _segmentSamples;     // 343980
 
-            // Compute strides for flattened buffer
+            var stemStride    = chCnt * length;
-            var stemStride    = chCnt * length; // 2 * N
+            var channelStride = length;
-            var channelStride = length;         // N
 
-            // Overlap-add
             for (var stem = 0; stem < stemCnt; stem++)
             {
                 for (var ch = 0; ch < chCnt; ch++)
@@ -119,7 +100,6 @@ public sealed class Htdemucs6sSeparator : IStemSeparator
                     {
                         var w = window[s];
                         var v = buf[baseIndex + s];
-
                         outStems[stem, ch, start + s] += v * w;
                     }
                 }
@@ -131,7 +111,6 @@ public sealed class Htdemucs6sSeparator : IStemSeparator
             await progress.ReportProgress((double)(i + 1) / nChunks, ct);
         }
 
-        // 5. Normalize by weight
         for (var stem = 0; stem < _stemNames.Length; stem++)
         {
             for (var ch = 0; ch < _channels; ch++)
@@ -145,12 +124,12 @@ public sealed class Htdemucs6sSeparator : IStemSeparator
             }
         }
 
-        // 6. Write stems
         var result = new List<StemTrack>();
         for (var i = 0; i < _stemNames.Length; i++)
         {
             var name = $"{Path.GetFileNameWithoutExtension(request.SourceFilePath)}_{_stemNames[i]}.flac";
             var path = Path.Combine(request.OutputDirectory, name);
+
             WriteFlac(path, outStems, i, totalSamples);
 
             result.Add(new StemTrack
@@ -174,7 +153,8 @@ public sealed class Htdemucs6sSeparator : IStemSeparator
     private StemSet? CheckExistingStems(StemSeparationRequest request)
     {
         var filesToCheck = Enum.GetNames(typeof(StemType))
-            .Select(stemType => (stemType, Path.Combine(request.OutputDirectory, $"{Path.GetFileNameWithoutExtension(request.SourceFilePath)}_{stemType}.flac")))
+            .Select(stemType => (stemType, Path.Combine(request.OutputDirectory,
+                $"{Path.GetFileNameWithoutExtension(request.SourceFilePath)}_{stemType}.flac")))
             .ToList();
 
         var stems = new List<StemTrack>();
@@ -188,7 +168,7 @@ public sealed class Htdemucs6sSeparator : IStemSeparator
         {
             using var reader = new AudioFileReader(f.Item2);
 
-            var stem =new StemTrack
+            stems.Add(new StemTrack
             {
                 Type = Enum.Parse<StemType>(f.Item1),
                 Name = Path.GetFileName(f.Item2),
@@ -196,18 +176,12 @@ public sealed class Htdemucs6sSeparator : IStemSeparator
                 SampleRate = reader.WaveFormat.SampleRate,
                 Channels = reader.WaveFormat.Channels,
                 Duration = reader.TotalTime
-            };
+            });
-
-            stems.Add(stem);
         }
 
         return stems.Count > 0 ? set : null;
     }
 
-    // ------------------------------
-    // Helpers
-    // ------------------------------
-
     private static float[] MakeWindow(int n, int overlap)
     {
         var w = new float[n];
@@ -245,59 +219,38 @@ public sealed class Htdemucs6sSeparator : IStemSeparator
         return result;
     }
 
-    //private static void WriteWave(string path, float[,,] stems, int stemIndex, int totalSamples)
-    //{
-    //    var format = WaveFormat.CreateIeeeFloatWaveFormat(_sampleRate, _channels);
-
-    //    using var writer = new WaveFileWriter(path, format);
-
-    //    for (int i = 0; i < totalSamples; i++)
-    //    {
-    //        writer.WriteSample(stems[stemIndex, 0, i]);
-    //        writer.WriteSample(stems[stemIndex, 1, i]);
-    //    }
-    //}
-
     private static void WriteFlac(string path, float[,,] stems, int stemIndex, int totalSamples)
     {
-        var psi = new ProcessStartInfo
+        var cmd =
-        {
-            FileName = "ffmpeg",
-            Arguments =
             "-y " +
-            "-f f32le " +                 // raw float32 little-endian
+            "-f f32le " +
-            "-ar 44100 " +                // sample rate
+            "-ar 44100 " +
-            "-ac 2 " +                    // channels
+            "-ac 2 " +
-            "-i pipe:0 " +                // read from stdin
+            "-i pipe:0 " +
-            "-compression_level 12 " +    // max FLAC compression
+            "-compression_level 12 " +
-            $"\"{path}\"",
+            $"\"{path}\"";
-            RedirectStandardInput = true,
-            RedirectStandardError = true,
-            RedirectStandardOutput = true,
-            UseShellExecute = false,
-            CreateNoWindow = true,
-            WindowStyle = ProcessWindowStyle.Hidden,
-        };
 
-        using var ff = Process.Start(psi) ?? throw new InvalidOperationException("Failed to start FFmpeg process");
+        using var ff = new FfmpegProcess(
-        using var stdin = ff.StandardInput.BaseStream;
+            name: $"flac:{Path.GetFileName(path)}",
+            commandLine: cmd,
+            redirectOutput: true,
+            redirectInput: true);
 
-        // Write raw float32 PCM directly to FFmpeg
+        ff.StartProcess();
-        var buffer = new byte[sizeof(float) * 2]; // stereo frame
+
+        var stdin = ff.Stdin!;
+        var frame = new byte[sizeof(float) * 2];
 
         for (var i = 0; i < totalSamples; i++)
         {
-            BitConverter.TryWriteBytes(buffer.AsSpan(0, 4), stems[stemIndex, 0, i]);
+            BitConverter.TryWriteBytes(frame.AsSpan(0, 4), stems[stemIndex, 0, i]);
-            BitConverter.TryWriteBytes(buffer.AsSpan(4, 4), stems[stemIndex, 1, i]);
+            BitConverter.TryWriteBytes(frame.AsSpan(4, 4), stems[stemIndex, 1, i]);
-            stdin.Write(buffer, 0, buffer.Length);
+            stdin.Write(frame, 0, frame.Length);
         }
 
         stdin.Flush();
         stdin.Close();
 
-        ff.WaitForExit();
+        ff.Proc!.WaitForExit();
     }
-
-
-
 }

AudioCore/Impl/RubberBandTimeStretchEngine.cs

@@ -9,7 +9,7 @@ public sealed class RubberBandTimeStretchEngine : ITimeStretchEngine, IDisposabl
     private readonly int             _sampleRate;
     private readonly int             _channels;
 
-    private Process? _ff;
+    private FfmpegProcess?           _ff;
     private Stream?                  _stdin;
     private Stream?                  _stdout;
 
@@ -29,11 +29,8 @@ public sealed class RubberBandTimeStretchEngine : ITimeStretchEngine, IDisposabl
         _sampleRate = sampleRate;
         _channels = channels;
 
-        // Ring buffer: e.g. 1 second of audio
         var bytesPerSecond = sampleRate * channels * sizeof(float);
         _ring = new byte[bytesPerSecond];
-
-        StartProcess();
     }
 
     public void Configure(PlaybackSpeedSettings settings)
@@ -54,7 +51,6 @@ public sealed class RubberBandTimeStretchEngine : ITimeStretchEngine, IDisposabl
         {
             var buf = _pool.Rent(expectedFloats);
             Array.Copy(input.Buffer.Samples, buf.Samples, input.Buffer.Length);
-
             return new TimeStretchedAudioBlock(buf, input.Frames, _channels, _sampleRate);
         }
 
@@ -72,7 +68,6 @@ public sealed class RubberBandTimeStretchEngine : ITimeStretchEngine, IDisposabl
         var outBytes = MemoryMarshal.AsBytes(outBuf.Span);
 
         var readBytes = DrainRing(outBytes, expectedBytes);
-
         if (readBytes <= 0)
         {
             outBuf.Dispose();
@@ -104,38 +99,34 @@ public sealed class RubberBandTimeStretchEngine : ITimeStretchEngine, IDisposabl
             Thread.Sleep(2);
         }
 
+        Debug.WriteLine("Rubberband: Timeout waiting for output from ffmpeg");
         return 0;
     }
 
-
-
     private void StartProcess()
     {
-        var psi = new ProcessStartInfo
+        var cmd =
-        {
-            FileName = "ffmpeg",
-            Arguments =
             $"-hide_banner -loglevel error " +
             $"-f f32le -ar {_sampleRate} -ac {_channels} -i pipe:0 " +
             $"-af \"rubberband=tempo={_speed}\" " +
-                $"-f f32le -ar {_sampleRate} -ac {_channels} pipe:1",
+            $"-f f32le -ar {_sampleRate} -ac {_channels} pipe:1";
-            RedirectStandardInput  = true,
-            RedirectStandardOutput = true,
-            UseShellExecute        = false,
-            CreateNoWindow         = true,
-            WindowStyle            = ProcessWindowStyle.Hidden,
-        };
 
-        _ff     = System.Diagnostics.Process.Start(psi);
+        _ff = new FfmpegProcess(
-        _stdin  = _ff!.StandardInput.BaseStream;
+            name: $"rubberband:{_speed:F3}",
-        _stdout = _ff!.StandardOutput.BaseStream;
+            commandLine: cmd,
+            redirectOutput: true,
+            redirectInput: true);
+
+        _ff.StartProcess();
+
+        _stdin = _ff.Stdin!;
+        _stdout = _ff.Stdout!;
 
         _readerRunning = true;
         _readerThread = new Thread(ReaderLoop) { IsBackground = true };
         _readerThread.Start();
     }
 
-
     private void RestartProcess()
     {
         DisposeProcess();
@@ -152,7 +143,6 @@ public sealed class RubberBandTimeStretchEngine : ITimeStretchEngine, IDisposabl
             while (_readerRunning)
             {
                 var read = _stdout!.Read(buf, 0, buf.Length);
-
                 if (read <= 0)
                     break;
 
@@ -171,7 +161,7 @@ public sealed class RubberBandTimeStretchEngine : ITimeStretchEngine, IDisposabl
                 }
             }
         }
-        catch { /* swallow for now */ }
+        catch { }
     }
 
     private int DrainRing(Span<byte> dest, int maxBytes)
@@ -203,7 +193,6 @@ public sealed class RubberBandTimeStretchEngine : ITimeStretchEngine, IDisposabl
         }
     }
 
-
     private void ResetRing()
     {
         lock (_ringLock)
@@ -216,9 +205,9 @@ public sealed class RubberBandTimeStretchEngine : ITimeStretchEngine, IDisposabl
     private void DisposeProcess()
     {
         _readerRunning = false;
+
         try { _stdout?.Close(); } catch { }
         try { _stdin?.Close(); } catch { }
-        try { _ff?.Kill(); } catch { }
         try { _ff?.Dispose(); } catch { }
 
         if (_readerThread != null)
@@ -226,6 +215,10 @@ public sealed class RubberBandTimeStretchEngine : ITimeStretchEngine, IDisposabl
             try { _readerThread.Join(500); } catch { }
             _readerThread = null;
         }
+
+        _ff = null;
+        _stdin = null;
+        _stdout = null;
     }
 
     public void Dispose() => DisposeProcess();

AudioCore_Tests/FfmpegAudioReader_Tests.cs

@@ -129,8 +129,11 @@ public sealed class FfmpegAudioReader_Tests
                 WindowStyle = ProcessWindowStyle.Hidden,
             };
 
-            using (var p = Process.Start(psi))
+            using (var p = Process.Start(psi) ?? throw new InvalidOperationException("Failed to start FFmpeg process"))
             {
+                // Start draining stderr immediately
+                _ = Task.Run(() => DrainStderr(p));
+
                 p!.WaitForExit();
                 Assert.AreEqual(0, p.ExitCode, "FFmpeg failed to convert MP3 to FLAC");
             }
@@ -204,4 +207,24 @@ public sealed class FfmpegAudioReader_Tests
         }
     }
 
+    private static void DrainStderr(Process proc)
+    {
+        try
+        {
+            var reader = proc.StandardError;
+
+            // ffmpeg writes short lines, so ReadLine is fine
+            // If you want zero allocations, use ReadAsync into a rented buffer.
+            string? line;
+            while ((line = reader.ReadLine()) != null)
+            {
+                Debug.WriteLine(line);
+            }
+        }
+        catch (Exception ex)
+        {
+            Debug.WriteLine(ex.ToString());
+        }
+    }
+
 }

AudioCore_Tests/Pipeline_Integration_Tests.cs

@@ -79,6 +79,8 @@ public sealed class Pipeline_Integration_Tests
 
         using var ff = Process.Start(psi);
         var stdin = ff!.StandardInput.BaseStream;
+        // Start draining stderr immediately
+        _ = Task.Run(() => DrainStderr(ff));
 
         var running = true;
 
@@ -128,4 +130,24 @@ public sealed class Pipeline_Integration_Tests
 
         Assert.IsGreaterThan(0, read, "FLAC output is not decodable");
     }
+
+    private static void DrainStderr(Process proc)
+    {
+        try
+        {
+            var reader = proc.StandardError;
+
+            // ffmpeg writes short lines, so ReadLine is fine
+            // If you want zero allocations, use ReadAsync into a rented buffer.
+            string? line;
+            while ((line = reader.ReadLine()) != null)
+            {
+                Debug.WriteLine(line);
+            }
+        }
+        catch (Exception ex)
+        {
+            Debug.WriteLine(ex.ToString());
+        }
+    }
 }