Breaking changes

• IWaveProvider.Read signature changed from Read(byte[], int, int) to Read(Span<byte>). Existing callers with byte[] migrate via source.Read(buffer.AsSpan(offset, count)); implementations override Read(Span<byte>)
• ISampleProvider.Read signature changed from Read(float[], int, int) to Read(Span<float>) (same migration pattern)
• MidiIn, MidiOut, MidiInCapabilities, and MidiOutCapabilities moved from NAudio.Midi to NAudio.WinMM — all winmm.dll interop now lives in one assembly
• MmResult, MmException, and Manufacturers moved from NAudio.Core to NAudio.WinMM
• DirectSoundOut moved from NAudio.Core to NAudio.Dmo (DirectSound has always been Windows-only)
• New NAudio.Dmo package. DMO effects (echo, chorus, reverb, etc.), the DMO MP3 decoder (DmoMp3FrameDecompressor), the DMO resampler (ResamplerDmoStream), and DirectSoundOut carved out of NAudio.Wasapi. Namespaces preserved (NAudio.Dmo, NAudio.Dmo.Effect, NAudio.Wave for DirectSoundOut). Meta-package consumers see no change — NAudio.Dmo comes in transitively. Direct NAudio.Wasapi consumers who use the DMO/DirectSound types now need an explicit <PackageReference Include="NAudio.Dmo" />.
• NAudio.Midi is now cross-platform — its net9.0 target no longer P/Invokes winmm.dll
• MidiInMessageEventArgs.Timestamp and MidiInSysexMessageEventArgs.Timestamp are now TimeSpan (previously int milliseconds) — preserves full WinRT 100 ns resolution on the WinRT backend
• MidiIn.CreateSysexBuffers removed — MidiIn now allocates sysex receive buffers automatically inside Start()
• WasapiOut, WasapiCapture, and WasapiLoopbackCapture are now [Obsolete] in favour of the new WasapiPlayer / WasapiRecorder APIs (the legacy types still ship and continue to work)
• WasapiOut's embedded DMO resampler removed. Exclusive-mode callers whose source format is not natively supported now get a NotSupportedException from Init instead of silent on-the-fly resampling. Resample upstream (e.g. with MediaFoundationResampler), use shared mode (which still auto-converts via AutoConvertPcm), or switch to WasapiPlayerBuilder. Removes NAudio.Wasapi's only intra-assembly dependency on DMO.
• WaveOut and WaveIn now default to event-driven callbacks; the legacy window-based variants are renamed WaveOutWindow / WaveInWindow and live in NAudio.WinForms
• WaveInEventArgs now fires one event per WASAPI packet (previously batched). A new BufferSpan property exposes the data without copying through the existing Buffer byte array
• Several Mf* Media Foundation wrapper types are now internal — only MfActivate and MediaType remain public
• BufferedWaveProvider buffer duration is now set in the constructor (default 5 seconds); BufferLength and BufferDuration are read-only
• WaveBuffer is deprecated — use MemoryMarshal.Cast instead
• MMDevice.AudioClient is [Obsolete] because it created a new instance per access; use MMDevice.CreateAudioClient()
• PropertyStore[int] now resolves PropVariant values safely; the indexer that returned the raw PropVariant is [Obsolete]
• Minimum target framework is now net9.0 (previously supported legacy .NET Framework and .NET Standard 2.0)
• CueWaveFileReader removed - use new WaveFileReader(...).Chunks.ReadCueList() to get a CueList

New features

• NAudio.SoundFile: new cross-platform SoundFileReader / SoundFileWriter wrapping libsndfile — reads and writes WAV/AIFF/FLAC/Ogg-Vorbis/Opus/MP3 on Linux, macOS and Windows (the first cross-platform FLAC/Vorbis/Opus encoder in NAudio). SoundFileReader is a WaveStream and ISampleProvider; both reader and writer also work over a System.IO.Stream. Requires a system libsndfile; SoundFileCapabilities reports which codecs the build supports (#1289)
• WASAPI: new high-level WasapiPlayer and WasapiRecorder classes, built via WasapiPlayerBuilder / WasapiRecorderBuilder. Adds IAudioClient3 low-latency support, MMCSS thread priority, IAsyncDisposable, zero-copy buffer access, and process-specific loopback via WasapiRecorderBuilder.WithProcessLoopback()
• ASIO: new AsioDevice class replacing AsioOut as the primary ASIO interface. Adds explicit InitPlayback / InitRecording / InitDuplex modes, non-contiguous channel selection, per-channel Span<float> callbacks, Reinitialize() for driver-reset recovery, and per-buffer timing fields (SamplePosition, SystemTimeNanoseconds, Speed, SMPTE TimeCode)
• ASIO events: LatenciesChanged and ResyncOccurred surfaced separately; buffer-size changes routed through DriverResetRequest
• Media Foundation: MediaFoundationEncoder.EncodeToFlac for lossless FLAC output. The FLAC/ALAC selector now falls back correctly on rate + channels
• WinForms: WaveOutWindow and WaveInWindow available as window-callback variants of the modernised event-driven WaveOut / WaveIn
• DSP: new FftProcessor with real-input specialisation and precomputed windowing
• WAV chunks: new IWaveChunkInterpreter<T> extension point, with built-in interpreters for cue lists, BWF bext (v1 and v2), and LIST/INFO metadata. RF64 promotion is now an explicit WaveFileWriterOption
• Span<T> overloads: added on BiQuadFilter.Transform, ALawDecoder.Decode, MuLawDecoder.Decode, and IMp3FrameDecompressor.DecompressFrame (default interface method preserves backward compatibility with NLayer and other third-party decoders)
• MIDI: new WinRTMidiIn / WinRTMidiOut classes in NAudio.Wasapi backed by Windows.Devices.Midi, with MidiMessageConverter for interop with the WinRT MIDI types. New IMidiInput / IMidiOutput interfaces (with a Send(MidiEvent) extension) let callers write backend-agnostic code; legacy MidiIn / MidiOut also implement them
• MIDI: MidiFile now reads RIFF-RMID (.rmi) files by unwrapping the RIFF container and parsing the embedded standard MIDI file (#1236)
• ALSA (Linux): new NAudio.Alsa package — AlsaOut (IWavePlayer) and AlsaIn (IWaveIn) backed by libasound, plus AlsaDeviceEnumerator. Linux-only ([SupportedOSPlatform("linux")], AOT-compatible [LibraryImport]); reference it explicitly, it is not part of the NAudio meta-package (#1182)

Demo apps and Test Harnesses

• NAudioConsoleTest: new CLI test harness for driving various NAudio features without the need for GUI. Includes run-batch for JSON-driven test plans and diagnose for capturing a structured host audio snapshot (OS, ASIO drivers, WASAPI/WinMM/DirectSound devices, NAudio assembly versions).
• WPF demos: spectrum analyser rewritten with corrected dB formula (20·log₁₀), log-frequency mapping, real-input full-scale calibration, bars instead of polylines, peak-decay markers, and per-band smoothing. New LiveWaveformControl with configurable render styles, vertical scaling, and fill-between rendering
• WAV recording demo: added loopback support and a multi-API device combo with provenance embedding
• MIDI In demo: Refresh button for hot-plugged devices, device combos disabled while in use, test MIDI Out plays on channel 1 (was 2), Filter Auto-Sensing on by default, stopping test output now sends note-off so notes don't hang, and cleaner panel disposal
• MfStressTest: Reliability tests for the new Media Foundation interop implementation in NAudio 3.
• Replaced vendored NSpeex (deprecated) with Opus (Concentus) in the network chat demo; added round-trip unit tests

Performance

• Vectorised mix-add and volume kernels via System.Numerics.Tensors — significantly faster on AVX2 hardware for typical buffer sizes
• Eliminated per-Read allocations in SmbPitchShiftingSampleProvider
• WaveStream.Read(Span<byte>) overridden directly on every concrete reader (no intermediate byte-array copy)
• WasapiCapture capture path is now zero-copy via the native WASAPI buffer span
• BiQuadFilter state and coefficient fields hoisted to locals in batch loops for register retention
• Mp3FileReader now builds its table-of-contents lazily on first seek instead of eagerly during construction; the Position setter no longer blocks; rapid scrub seeks debounce and silence output
• Eliminated per-Read allocations in ResamplerDmoStream and DmoMp3FrameDecompressor (cached input buffer and output-buffer array) (#971)

Reliability and bug fixes

• AcmInterop: serialised all msacm32 P/Invokes process-wide via a reentrant lock — fixes process-killing access violations under concurrent ACM access
• AcmStream: fixed double-close in finalizer by zeroing the handle field before close
• MediaFoundationReader: informational source-reader flags (STREAMTICK, NEWSTREAM, NativeMediaTypeChanged, AllEffectsRemoved) are now non-fatal instead of aborting reads
• MediaFoundationReader.Reposition: fixed using a stale field instead of the parameter (seeks would default to stream start)
• MediaFoundationEncoder: unselected MediaType instances are now disposed to prevent finalizer-thread COM ref leaks
• Mp3FileReader: fixed false sample-rate-change errors near end of file
• MP3 frame parsing: more robust against false frame detections from album art and trailing metadata
• MidiFile: preserved running-status across meta events (fixes "Read too far" errors when meta events interrupt running-status sequences)
• WaveStream.CurrentTime setter: now lands on a block boundary, preventing garbage audio on seek in custom readers
• BlockAlignReductionStream.Position setter: now validates the incoming value instead of the stale current position, so a block-aligned seek after an arbitrary-length read no longer wrongly throws "Position must be block aligned" (#368)
• IconExtractor.Extract: now guards against null icon handles from ExtractIconEx
• DirectSoundOut.InitializeDirectSound: wrapped notification setup in try/finally to prevent COM ref leak on SetNotificationPositions failure
• ASIO: implemented missing Asio64Bit conversions (Int24LSB and Float32LSB output sample types)
• ASIO: fixed byte-order bug in AsioDriver.GetSamplePosition for Asio64Bit reassembly
• WdlResampler: backported three upstream Cockos WDL bug fixes (latency calculation, ResampleOut clamping, Blackman-Harris window correction)
• MediaBufferLease: hardened against out-of-order disposal
• Added finalizers to DMO MediaBuffer and the Mf* wrappers that hold (RCW, IntPtr) pairs to prevent COM ref leaks
• WaveFileChunkReader: fixed ArgumentException parsing WAV files whose odd-length chunks are followed by non-UTF-8 bytes — the word-alignment pad-byte check no longer decodes via BinaryReader.PeekChar(), and is now guarded against end-of-stream (#959)
• Clarified BiQuadFilter q parameter docs (#1264)
• Removed dead naudio.codeplex.com links from README, MixDiff Help menu, and source comments (CodePlex was shut down by Microsoft in 2017) (#985)
• AudioClient.Dispose: made idempotent and safe against concurrent/re-entrant disposal — fixes an intermittent NullReferenceException from the COM interop layer when a WASAPI capture or playback wrapper is disposed more than once (#1183)
• WaveFileReader / AiffFileReader: malformed headers that declared BlockAlign=0 now throw InvalidDataException from the constructor instead of DivideByZeroException from the Position setter (#1254)
• AiffFileReader.Read: truncated SSND chunks no longer trigger IndexOutOfRangeException in the byte-swap loop — the read count is rounded down to a whole block (#1254)

Modernisation (Native AOT, source-generated COM)

• NAudio.Core, NAudio.Midi, and NAudio.Wasapi are now IsAotCompatible=true. AOT compatibility is enforced at build-time by NAudioAotSmokeTest, which fails CI on any new trim or AOT analyzer warning
• Most COM interop migrated from [ComImport] to [GeneratedComInterface] / ComWrappers. Affected interfaces include the WASAPI / Core Audio activation chain (IActivateAudioInterfaceCompletionHandler, IMMNotificationClient, IAudioSessionNotification, IAudioSessionEvents, IAudioEndpointVolumeCallback, IAgileObject, IPropertyStore), the Media Foundation cascade, the DMO interfaces, DirectSound, and the ComStream CCW (now source-generated IStream)
• DirectSound P/Invokes migrated to [LibraryImport] with [UnmanagedCallersOnly] thunks; BufferDescription and BufferCaps converted from class to struct
• AcmDriver ported from legacy NativeMethods to NativeLibrary
• Most MediaFoundationInterop blittable P/Invokes migrated to [LibraryImport]

Packaging and dependencies

• Each NAudio package now ships its own README in the NuGet payload
• Test project migrated from VSTest to Microsoft.Testing.Platform
• NAudioTests split into NAudio.Core.Tests (cross-platform, net10.0) and NAudio.Windows.Tests (Windows-only, net10.0-windows) — eliminates the dual-TFM double-run on Windows CI and lets non-Windows devs run just the cross-platform suite
• NAudio.Alsa.Tests and NAudio.SoundFile.Tests now ignore MTP exit codes 8/9 so dotnet test succeeds on machines where the suite legitimately runs zero tests (ALSA off-Linux) or self-skips (libsndfile absent)
• Migrated to the modern .slnx solution format
• Renamed license.txt to LICENSE for GitHub license detection; refreshed copyright year to 2008–2026
• Added per-package <Description> metadata to every shipping NAudio NuGet package so each clearly identifies itself as part of the NAudio family