Documentation
¶
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type AGC ¶
type AGC struct {
Reference float32 // target output magnitude (default 1.0)
Rate float32 // adaptation step (typical 1e-3 to 1e-2)
MaxGain float32 // ceiling to avoid runaway on dead-air
// contains filtered or unexported fields
}
AGC is a feedback automatic-gain-control loop that drives the average magnitude of a complex IQ stream toward Reference.
type AudioAGC ¶
type AudioAGC struct {
// contains filtered or unexported fields
}
AudioAGC is the real-valued counterpart of AGC, sized for the post-demod chain in internal/voice/composer. The IQ-domain AGC drives the *complex* baseband magnitude toward a target with a single adaptation rate, which works because FM has a constant envelope on air. After demod the signal is voice — bursty, with short loud transients separated by quieter passages — so a single rate either pumps badly (too fast) or never catches up (too slow).
AudioAGC is a classic envelope-follower + gain stage:
abs = |x| if abs > level: level += (1 - α_attack) × (abs - level) // ramp up fast else: level += (1 - α_release) × (abs - level) // ramp down slow gain = clamp(reference / max(level, floor), 0, MaxGain) y[n] = x[n] × gain
Attack / release are time constants (in samples after construction); short attack catches transients before they clip, long release keeps the gain steady through speech gaps so the output doesn't pump. Reference is the target |y| ≈ Reference; pick something that leaves headroom for downstream stages (typical 0.3 keeps int16 conversion comfortably under MaxInt16 at the existing 10 000-scale in voice/composer).
AudioAGC is not safe for concurrent Process calls — pin it to a single demod goroutine and Reset between calls.
func NewAudioAGC ¶
func NewAudioAGC(cfg AudioAGCConfig) *AudioAGC
NewAudioAGC builds an envelope-follower-based AGC. Bad parameters trip a panic at startup so misconfiguration shows up loudly rather than silently producing wrong audio.
func (*AudioAGC) Gain ¶
Gain returns the current adaptive gain. Useful for diagnostics; not needed for normal operation.
type AudioAGCConfig ¶
type AudioAGCConfig struct {
Reference float32 // target |output| (default 0.3)
Attack time.Duration // ramp-up time constant (default 5 ms)
Release time.Duration // ramp-down time constant (default 200 ms)
MaxGain float32 // ceiling on adaptive gain (default 64.0)
SampleRate float64 // sample rate of the audio stream (Hz, required)
}
AudioAGCConfig configures NewAudioAGC. All time constants are in real time; the constructor folds in the sample rate.
type RealResampler ¶
type RealResampler struct {
L, M int
// contains filtered or unexported fields
}
RealResampler is the real-valued counterpart of Resampler. Same polyphase decomposition, same L/M rate, but operates on float32 audio instead of complex64 IQ. Sized for the post-demod chain in internal/voice/composer where the FM demod hands real audio to a resampler that retunes 48 kHz → 8 kHz (or arbitrary rational ratios) with proper anti-aliasing built into the polyphase prototype filter.
The complex Resampler stays where it is — IQ paths still want it. Splitting them keeps each loop hot on the right data type without the complex64 ↔ float32 conversion overhead that an interface would impose.
RealResampler is not safe for concurrent Process calls — pin it to a single demod goroutine and Reset between calls.
func NewRealResampler ¶
func NewRealResampler(L, M, tapsPerBranch int, beta float64) *RealResampler
NewRealResampler builds a real-valued resampler with rate L/M using a Kaiser-window LPF of total length tapsPerBranch*L. Cutoff is min(0.5/L, 0.5/M) so the prototype rejects images and aliases for both the interpolation and decimation steps. Bad parameters trip a panic at construction so misconfiguration shows up loudly.
func (*RealResampler) Process ¶
func (r *RealResampler) Process(dst, src []float32) []float32
Process consumes len(src) input samples and returns approximately len(src)*L/M output samples. dst is reused if it has capacity.
func (*RealResampler) Reset ¶
func (r *RealResampler) Reset()
Reset clears the running history and commutator state so the next Process call starts from silence.
type Resampler ¶
type Resampler struct {
L, M int
// contains filtered or unexported fields
}
Resampler is a polyphase rational resampler with rate L/M. It interpolates by L (using polyphase branches of an LPF) and decimates by M.
func NewResampler ¶
NewResampler builds a resampler with rate L/M using a Kaiser-window LPF of total length tapsPerBranch*L. Cutoff is min(0.5/L, 0.5/M) so that the filter rejects images and aliases for both interpolation and decimation.
Source Files
Directories
¶
| Path | Synopsis |
|---|---|
|
Package channelizer implements an M-channel critically-sampled polyphase channelizer.
|
Package channelizer implements an M-channel critically-sampled polyphase channelizer. |
|
Package demod contains baseband demodulators that convert IQ streams into real-valued symbol streams (or audio, for FM).
|
Package demod contains baseband demodulators that convert IQ streams into real-valued symbol streams (or audio, for FM). |
|
Package diversity combines IQ streams from N receivers tuned to the same frequency into a single per-sample IQ stream that's stronger and less faded than any one source.
|
Package diversity combines IQ streams from N receivers tuned to the same frequency into a single per-sample IQ stream that's stronger and less faded than any one source. |
|
Package equalizer implements adaptive channel equalizers used to fight simulcast distortion — the inter-symbol interference produced when multiple transmitters cover the same frequency at slightly different arrival delays at the receiver.
|
Package equalizer implements adaptive channel equalizers used to fight simulcast distortion — the inter-symbol interference produced when multiple transmitters cover the same frequency at slightly different arrival delays at the receiver. |
|
Package fft provides a swappable FFT abstraction.
|
Package fft provides a swappable FFT abstraction. |
|
Package filter implements the FIR/CIC/halfband primitives used by the DSP pipeline.
|
Package filter implements the FIR/CIC/halfband primitives used by the DSP pipeline. |
|
Package sync provides symbol-time recovery and frame sync correlators.
|
Package sync provides symbol-time recovery and frame sync correlators. |
|
Package window provides standard window functions for FIR design and FFT pre-processing.
|
Package window provides standard window functions for FIR design and FFT pre-processing. |