Struct AmbeEncoder

Source

pub struct AmbeEncoder { /* private fields */ }

Expand description

Top-level D-STAR AMBE 3600×2400 encoder.

Owns one instance of every per-stream state object. Not thread-safe; construct one per concurrent voice stream.

§Usage

use mbelib_rs::AmbeEncoder;

let mut encoder = AmbeEncoder::new();
// Feed 160-sample (20 ms at 8 kHz) frames of f32 PCM in [-1.0, 1.0).
let pcm: [f32; 160] = [0.0; 160];
let ambe_frame: [u8; 9] = encoder.encode_frame(&pcm);

Implementations§

Source §

impl AmbeEncoder

Source

pub fn new() -> Self

Construct a fresh encoder using OP25’s single-frame (look-back + sub-multiples) pitch tracker. Zero added latency; each encode_frame call commits pitch for the just-received frame.

This is the backwards-compatible default. Real-voice inputs work well here because sub-multiples analysis resolves the common octave ambiguities; pure-sine synthetic tests can lose the 2P-vs-P disambiguation on settled tones. For the full OP25 pitch pipeline (2-frame look-ahead DP), see Self::new_with_lookahead — it costs 40 ms of latency and an extra 2-frame warmup but matches OP25’s pitch decisions on pure sines as well as voice.

Source

pub fn new_with_lookahead() -> Self

Construct a fresh encoder WITH the 2-frame look-ahead DP enabled. The first two encode_frame calls return AMBE_SILENCE while the pipeline fills; frame N-2’s pitch is committed on the third call (frame N). Adds ≈40 ms end-to-end latency; matches OP25’s pitch-tracking behaviour across pure sines and pitch transitions.

Source

pub fn encode_frame(&mut self, pcm: &[f32]) -> [u8; 9]

Encode one 20 ms PCM frame into a 9-byte AMBE wire frame.

pcm must contain at least 160 f32 samples in [-1.0, 1.0). Convert from i16 by dividing by 32768.0.

§Output

Returns a 9-byte D-STAR AMBE frame. Silent or near-silent input (pitch tracker confidence below SILENCE_CONFIDENCE) short-circuits to the canonical AMBE_SILENCE pattern that MMDVMHost and DVSI chips use for zero-audio frames, so silent stretches stay wire-compatible with conformant receivers.

§Panics

Never panics under normal use. The look-ahead pipeline’s internal invariant — self.pending is Some iff the encoder was built with Self::new_with_lookahead — is enforced at construction and never mutated afterwards; the unreachable expect is kept as a defensive check rather than removed entirely.

Source