Algorithms#

Supplied Processing Algorithms#

SOF provides an extensive ecosystem of permissively-licensed and royalty-free audio processing algorithms that can be used alongside proprietary processing components to build production audio pipelines.

In addition to upstream native algorithms, open-source and partner processing algorithms from ecosystem providers (including FFmpeg, WebRTC, Valve Steam Audio, DTS, Dolby, Google, Realtek, Cadence, CMSIS-DSP, and vendor DSP libraries) can be compiled as dynamically loadable modules (e.g. Zephyr LLEXT / ELF modules) or integrated into active audio pipelines. This modular architecture allows open-source, vendor, and proprietary intellectual property (IP) components to be safely integrated into the same pipeline graph without license contamination or monolithic recompilation.

Table 3 SOF Supported Audio Processing Modules & Algorithms#

Provider

Algorithm

Category

SIMD

Key Capabilities

Status

icon_prov_sof SOF

Volume / Mute

Basic Routing & Level

ARM, HiFi 3, HiFi 4, HiFi 5, RISCV, Scalar C

Per-channel linear and log gain curves; Smooth zipper noise attenuation; Zero-overhead bypass when set to 0dB

Upstream

icon_prov_sof SOF

Audio Mixer

Basic Routing & Level

ARM, HiFi 3, HiFi 5, RISCV, Scalar C

Concurrent playback mixing; Dynamic input stream attachment/detachment; Saturation and clipping protection

Upstream

icon_prov_sof SOF

Sample Rate Converter (SRC)

Foundational DSP

HiFi 2 EP, HiFi 3, HiFi 4, HiFi 5, RISCV, Scalar C

High SNR polyphase filtering; Low group delay; Multi-channel synchronous resampling

Upstream

icon_prov_sof SOF

Asynchronous SRC (ASRC)

Foundational DSP

HiFi 3, HiFi 5, RISCV, Scalar C

Farrow polynomial interpolation; Continuous clock drift tracking; Decoupled clock domain bridging

Upstream

icon_prov_sof SOF

Digital Microphone (DMIC) Decimation & Array Tuning

Foundational DSP

Hardware Accelerator, Scalar C

5th-order Cascaded Integrator-Comb (CIC) filter with up to 31x decimation; Multirate droop-compensating FIR filters with passband ripple < 0.1 dB and stopband > 90 dB; Dual-FIFO mode matching for concurrent 48 kHz communications and 16 kHz wake-on-voice; Acoustic sensitivity calibration and inter-channel gain trimming for beamforming arrays; Automated logarithmic unmute gain ramping eliminating stream start pops; Standalone Python calibration CLI (sof_dmic_tool.py) and ACPI NHLT / Topology 2 integration

Upstream

icon_prov_sof SOF

Audio Demux

Basic Routing & Level

Scalar C

Multi-channel stream demultiplexing; Dynamic route splitting; Zero-copy sample extraction

Upstream

icon_prov_sof SOF

Audio Mux

Basic Routing & Level

Scalar C

Multi-source stream multiplexing; Configurable input channel mapping; Synchronized buffer alignment

Upstream

icon_prov_sof SOF

Channel Map / Remap

Basic Routing & Level

Scalar C

Arbitrary slot and channel routing; Mono to stereo/surround replication; Channel swap and mute masking

Upstream

icon_prov_sof SOF

Level Multiplier

Basic Routing & Level

HiFi 3, HiFi 4, HiFi 5, Scalar C

High-precision Q9.23 fixed-point multiplier (-138.47 dB to +48.17 dB); Zero-overhead fast-path bypass when configured for unity gain (0 dB); Runtime IPC4 calibration and LLEXT dynamic module packaging

Upstream

icon_prov_sof SOF

Up/Down Mixer

Basic Routing & Level

HiFi 3, HiFi 4, HiFi 5, Scalar C

Matrix coefficients for stereo, surround 5.1, and 7.1 mapping; Channel energy normalization and clipping prevention; Zero-copy passthrough when channel geometry matches

Upstream

icon_prov_sof SOF

Tone Generator

Diagnostics & Testing

RISCV, Scalar C

Sine wave generation; Configurable frequency and amplitude; Per-channel tone routing

Upstream

icon_prov_sof SOF

Parametric Equalizer (EQ FIR)

Audio Enhancement

ARM, HiFi 2 EP, HiFi 3, HiFi 4, HiFi 5, RISCV, Scalar C

High-order linear-phase FIR filtering; Speaker and room impulse response correction; Live runtime coefficient updates over IPC

Upstream

icon_prov_sof SOF

Parametric Equalizer (EQ IIR)

Audio Enhancement

ARM, HiFi 2 EP, HiFi 3, HiFi 4, HiFi 5, RISCV, Scalar C

Cascaded second-order biquad sections; Parametric peak, notch, low/high shelf; Low computational latency

Upstream

icon_prov_sof SOF

Aria (Automatic Regressive Input Amplifier)

Audio Enhancement

HiFi 3, HiFi 4, HiFi 5, Scalar C

Target pre-amplification boost (0, 6, 12, 18 dB); Instantaneous regressive ducking to prevent 0 dBFS clipping; 1ms lookahead circular buffer and per-sample linear interpolation

Upstream

icon_prov_sof SOF

Dynamic Range Compressor (DRC)

Audio Enhancement

ARM, HiFi 3, HiFi 4, RISCV, Scalar C

Speaker excursion and thermal protection; Configurable attack, release, and knee; Peak and RMS signal level detection

Upstream

icon_prov_sof SOF

Multiband DRC

Audio Enhancement

HiFi 3, HiFi 4, RISCV, Scalar C

Subband crossover splitting; Per-band threshold and ratio controls; Comprehensive speaker protection

Upstream

icon_prov_sof SOF

Crossover Filter

Audio Enhancement

HiFi 3, RISCV, Scalar C

Linkwitz-Riley 4th order (LR4) splitting; Flat magnitude sum across crossover point; Multi-way woofer, tweeter, and sub routing

Upstream

icon_prov_sof SOF

DC Blocker

Audio Enhancement

ARM, HiFi 3, HiFi 4, RISCV, Scalar C

Removes DC bias from digital mics and ADCs; Sub-audible rumble attenuation; Near-zero phase distortion in audio band

Upstream

icon_prov_sof SOF

Phase Vocoder

Audio Enhancement

HiFi 3, Scalar C

Real-time Short-Time Fourier Transform (STFT) analysis & synthesis; Variable speed scaling (0.5x to 2.0x) with exact GCD counter normalization; Interactive phase re-anchoring and mono downmix optimization

Upstream

icon_prov_sof SOF

STFT Process

Audio Enhancement

HiFi 3, Scalar C

Multi-channel 32-bit forward and inverse FFT with COLA windowing; Dual-domain processing: Cartesian complex and polar magnitude/phase; Single contiguous buffer layout and zero-copy polar memory overlay

Upstream

icon_prov_sof SOF

Smart Amp Protection (DSM)

Speaker Protection

HiFi 3, HiFi 4, Scalar C

Real-time voice coil temperature estimation via continuous Re(t) tracking; Nonlinear membrane excursion prediction and adaptive high-pass limiting; Closed-loop hardware I/V sense feedback via SoundWire and I2S/TDM; Two-layer modular architecture supporting Maxim DSM and vendor engines; Live runtime parameter injection and telemetry readback via sof-ctl

Upstream

icon_prov_sof SOF

Sound Dose & Exposure

Speaker Protection

HiFi 3, Scalar C

IEC 61672-1 Class 1 A-weighting cascaded Direct Form I IIR biquad filtering; Overflow-proof 64-bit real-time energy accumulation and integer base-2 logarithm decibel conversion; Autonomous 1-second asynchronous IPC4 notification dispatch without host polling; Smooth per-frame exponential slew gain limiter (0.05 dB/frame) eliminating clicks and pops; Acoustic laboratory HATS calibration, rolling 7-day CSD tracking, and runtime control via sof-ctl

Upstream

icon_prov_dolby Dolby

Dolby Audio Processing (DAP)

Audio Enhancement

HiFi 3, HiFi 4, HiFi 5, Scalar C

Intelligent volume leveling and dynamic range management; Dialog enhancer and surround sound virtualizer; Custom speaker acoustic tuning and distortion limiting

Vendor Extension

icon_prov_sof SOF

Beamformer (TDFB)

Voice & Telephony

HiFi 2 EP, HiFi 3, HiFi 4, HiFi 5, RISCV, Scalar C

Multi-mic circular and linear array support; Broadside and endfire steering; Spatial diffuse noise suppression

Upstream

icon_prov_webrtc WebRTC

WebRTC Echo Cancellation (AEC)

Voice & Telephony

HiFi 3, HiFi 4, VFPU, Scalar C

Subband adaptive filter convergence; Multi-channel reference loopback alignment; Robust double-talk detection

Active Development

icon_prov_webrtc WebRTC

WebRTC Mobile AEC (AECM)

Voice & Telephony

HiFi 3, HiFi 4, VFPU, Scalar C

Fixed-point low-complexity processing; Optimized for earbuds and wearables; Low RAM and cycle footprint

Active Development

icon_prov_webrtc WebRTC

WebRTC Noise Suppression (NS)

Voice & Telephony

HiFi 3, HiFi 4, VFPU, Scalar C

Stationary background noise reduction; Configurable aggressiveness levels; Preserves speech formant clarity

Active Development

icon_prov_webrtc WebRTC

WebRTC Neural NS (NS2 / RNNoise)

Voice & Telephony

HiFi 3, HiFi 4, VFPU, Scalar C

Recurrent neural network (RNN) inference; Non-stationary transient noise elimination; High speech perceptual quality

Active Development

icon_prov_webrtc WebRTC

WebRTC Voice Activity Detector (VAD)

Voice & Telephony

HiFi 3, Scalar C

Multi-band energy likelihood estimation; Sub-frame voice decision gating; Ultra-low power listening states

Active Development

icon_prov_webrtc WebRTC

WebRTC Automatic Gain Control (AGC)

Voice & Telephony

HiFi 3, HiFi 4, Scalar C

Dynamic gain adjustment; Saturation prevention limiter; Normalizes quiet and loud speakers

Active Development

icon_prov_sof SOF

Key Phrase Buffer (KPB / WoV)

Voice & Telephony

Scalar C

Ultra-low power DSP listening mode (D0ix); Zero-latency audio pre-roll buffer playback; Multi-slot capture streaming to host

Upstream

icon_prov_google Google

microWakeWord (TFLite Micro)

Voice & Telephony

HiFi 3, HiFi 4, Scalar C

On-device neural network keyword spotting; TFLite Micro runtime execution; Low false-reject and false-alarm rates

Active Development

icon_prov_sof SOF

Mel-Frequency Cepstral Coefficients (MFCC)

Voice & Telephony

HiFi 3, HiFi 4, Scalar C

Configurable triangular Mel filterbanks (20 Hz to 8 kHz) with Slaney area normalization; Dual-mode operation: 80-bin Mel spectrogram (Whisper ASR) or 13-cepstra MFCC (TFLM microWakeWord); Discrete Cosine Transform (DCT-II) with sinusoidal cepstral liftering; Embedded Voice Activity Detection (VAD) and Discontinuous Transmission (DTX) silence suppression; Sparse packed triangular filterbank vector storage with >95% SRAM memory reduction

Upstream

icon_prov_sof SOF

Microphone Privacy Manager

Voice & Telephony

Scalar C

Zero-sample hardware mute interlock; GPIO privacy LED synchronization; Host-independent privacy state enforcement

Upstream

icon_prov_realtek Realtek

Realtek Neural Noise Reduction (RTNR)

Voice & Telephony

HiFi 4, Scalar C

Neural network recurrent inference; Non-stationary transient acoustic noise suppression; Dual-microphone directional voice enhancement

Upstream

icon_prov_cadence SOF / Cadence

Media Codecs (Cadence XA & Compress-Offload)

Codecs & Compression

HiFi 3, HiFi 4, HiFi 5, Scalar C

ALSA compress-offload playback (MP3, AAC, Vorbis, PCM passthrough) and capture (MP3 enc); Standardized Cadence Xtensa Audio (XA) four-class memory tables and state machine; Deep-buffer DMA host wakeup suppression enabling prolonged C10 deep sleep

Upstream

icon_prov_ffmpeg FFmpeg

AAC Decoder

Codecs & Compression

VFPU, HiFi 3, HiFi 4, HiFi 5, Scalar C

Vector floating-point hardware acceleration; MPEG-4 AAC-LC and HE-AAC profile support; Direct pipeline integration

Active Development

icon_prov_ffmpeg FFmpeg

AAC Encoder

Codecs & Compression

VFPU, HiFi 3, HiFi 4, HiFi 5, Scalar C

Low-power bitstream encoding; Configurable bitrates and sample rates; Optimized MDCT and psychoacoustic model

Active Development

icon_prov_ffmpeg FFmpeg

MP3 Decoder

Codecs & Compression

VFPU, HiFi 3, HiFi 4, HiFi 5, Scalar C

Hardware VFPU SIMD acceleration; High-throughput low-overhead DSP execution; Full bit reservoir and Huffman decoding

Active Development

icon_prov_ffmpeg FFmpeg

MP3 Encoder

Codecs & Compression

VFPU, HiFi 3, HiFi 4, Scalar C

Low-complexity fixed-point encoding; Efficient subband analysis filterbank; Standard MPEG-1 Layer III bitstream generation

Active Development

icon_prov_ffmpeg FFmpeg

FLAC Decoder

Codecs & Compression

VFPU, HiFi 3, HiFi 4, Scalar C

Lossless 16/24-bit audio decompression; Fast linear prediction decoding; Zero fidelity loss playback

Active Development

icon_prov_ffmpeg FFmpeg

Opus Decoder

Codecs & Compression

VFPU, HiFi 3, HiFi 4, Scalar C

SILK speech and CELT music mode support; Sub-20ms algorithmic latency; Dynamic bitrate and bandwidth adaptation

Active Development

icon_prov_ffmpeg FFmpeg

Vorbis Decoder

Codecs & Compression

VFPU, HiFi 3, HiFi 4, Scalar C

General-purpose variable bitrate decompression; Vector quantization floor decoding; Low memory footprint

Active Development

icon_prov_steam Steam Audio

Steam Audio Spatializer

Spatial Audio

VFPU, HiFi 4, HiFi 5, Scalar C

Spherical 3D sound positioning; Convolution-based HRTF binaural rendering; Dynamic listener and source orientation

Active Development

icon_prov_dts DTS

DTS Audio Processing / DTS:X

Spatial Audio

HiFi 3, HiFi 4, HiFi 5, Scalar C

Multichannel immersive 3D surround sound virtualization; Speaker and headphone acoustic correction and tuning; Dynamic dialog clarity enhancement and bass management

Vendor Extension

icon_prov_sof SOF

Real-Time Probes & Telemetry

Diagnostics & Tools

Scalar C

Direct probe DMA streaming over TCP port 9999; Zero overhead when probe taps are inactive; Multi-point simultaneous stream tapping

Upstream

Note

For detailed algorithm implementation guides, filter tuning workflows, and design tools, consult the 2. Audio Algorithm Tuning, Calibration & Runtime Control (Tuning) section in Developer Guides.