The 2:1 / 1:2 linear-dB compander pair. More...

#include <tape_machine_components.hpp>

Public Member Functions
void	prepare (double sample_rate)
void	reset () noexcept
double	encode (double x) noexcept
	Record side: 2:1 compression toward the reference.
double	decode (double x) noexcept
	Playback side: 1:2 expansion, exact inverse slope.

Static Public Attributes
static constexpr double	kAttackMs = 1.0
	[design parameter] default 1 ms, range 0.3–5 ms.
static constexpr double	kReleaseMs = 100.0
	[design parameter] default 100 ms, range 50–300 ms. Same honest gap.
static constexpr double	kRefLevelDbfs = -20.0
	0 dBr, in dBFS.

Detailed Description

template<typename SampleType = float>
class pulp::signal::TapeCompanderT< SampleType >

The 2:1 / 1:2 linear-dB compander pair.

Encode halves the programme's level in dB relative to a reference; decode doubles it back. The algebra is exact and worth writing out, because it is the whole reason the topology works: with L the input's level in dBr, encode applies −L/2, so the encoded signal sits at L/2 dBr; decode measures THAT and applies +L/2, returning L. Both stages are unity at the reference by construction, and a round trip with nothing in between is transparent — not approximately, identically.

The decoder tracks the ENCODED envelope rather than being handed the encoder's gain. That is the point: everything the tape does between them — loss, hiss, print-through — is inside the loop the decoder measures, so noise that entered after encoding gets expanded DOWN along with a quiet programme. A feed-forward "remember the gain and undo it" topology would leave the noise exactly where it was and do nothing at all.