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.Wasapi (DirectSound has always been Windows-only)
• NAudio.Midi is now cross-platform — its net9.0 target no longer P/Invokes winmm.dll
• WasapiOut, WasapiCapture, and WasapiLoopbackCapture are now [Obsolete] in favour of the new WasapiPlayer / WasapiRecorder APIs (the legacy types still ship and continue to work)
• 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

• 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)
• 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

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

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
• 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
• Clarified BiQuadFilter q parameter docs (#1264)

Modernisation (Native AOT, source-generated COM)

• NAudio.Core, NAudio.Midi, and NAudio.Wasapi are now IsAotCompatible=true. AOT compatibility is exercised end-to-end by NAudioAotSmokeTest in CI
• 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
• Replaced vendored NSpeex (deprecated) with Opus (Concentus) in the network chat demo; added round-trip unit tests
• Test project migrated from VSTest to Microsoft.Testing.Platform
• Migrated to the modern .slnx solution format
• Renamed license.txt to LICENSE for GitHub license detection; refreshed copyright year to 2008–2026