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audio-codec

real-time audio codec

Opus

SystemTechniques · 3Primitives · 14 audio-codec Packet loss concealmentmedia · medium: Synthesize missing audio frames from prior signal (pitch repetition, neural PLC)Psychoacoustic modelmedia · medium: Masking thresholds driving perceptual bit allocationSample rate conversionsignal-processing · medium: Polyphase and windowed-sinc resampling; asynchronous rate conversion for clock driftLinear predictive coding (LPC)media · low: Predict each sample from the previous p; code only the small prediction error plus p coefficients. Core of FLAC, speech codecs and the Opus SILK layer.›IIR and FIR filterssignal-processing · low: Two ways to shape a sampled signal's spectrum: FIR (finite taps, always stable, exact linear phase) or IIR (feedback, a few coefficients, cheap but phase-distorting).›SIMD programminghardware-os · low: Process 4-16 lanes per instruction with AVX2, AVX-512 or NEON via Rust std::arch, with runtime dispatch and a portable fallback.›Arithmetic codingcompression · low: Encodes a whole message as one number in [0,1), spending fractional bits per symbol; pairs with adaptive context models for the best ratios.›Vector quantizationcompression · low: Codebook and pyramid vector quantization of coefficient vectorsDeterministic fixed-point mathgame-networking · low: Bit-identical simulation math across CPUs, compilers and builds: integer fixed-point formats, the float traps (FMA, x87, fast-math, libm), deterministic trig, sqrt and RNG.›Voice activity detectionmachine-learning · low: Per-frame speech/non-speech decision with smoothing, from an energy threshold over a tracked noise floor up to small neural nets.›Modified dctnumerics · low: MDCT with TDAC windows for transform audio codingForward error correctionsignal-processing · low: Add redundancy (LDPC, Reed-Solomon, XOR parity) so receivers repair loss without retransmitRecurrent networksmachine-learning · low: GRU and LSTM cells for streaming sequence modelsFast Fourier transformnumerics · low: Computes the DFT in O(n log n) by recursively splitting into even and odd halves; the basis of fast convolution and spectral methods.›PRNGs (PCG, xoshiro)numerics · low: Small, fast, statistically strong non-cryptographic generators: PCG32 and xoshiro256**, with seeding, parallel streams and unbiased ranges.›Scalar quantizationsearch-sort · low: Per-dimension int8/binary quantization of vectors with rescoringBiquad filterssignal-processing · low: Second-order IIR sections (RBJ cookbook): low/high pass, peaking EQ; stable cascades

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