bw_bd_reduce

Bit depth reducer with input gate.

This is purely an audio effect, it doesn't actually produce an output signal with a different encoding. The algorithm is deliberately crude to obtain the characteristic noise due to lo-fi A/D quantization.

Examples

Here you can download one or more example VST3 plugins for Windows, macOS and Linux. Source code of the audio engine(s) is included in the archive(s).

VST® is a trademark of Steinberg Media Technologies GmbH, registered in Europe and other countries.

API

Module type: DSP

bw_bd_reduce_coeffs

typedef struct bw_bd_reduce_coeffs bw_bd_reduce_coeffs;

Coefficients and related.

bw_bd_reduce_init()

static inline void bw_bd_reduce_init(
	bw_bd_reduce_coeffs * BW_RESTRICT coeffs);

Initializes input parameter values in coeffs.

bw_bw_reduce_set_sample_rate()

static inline void bw_bd_reduce_set_sample_rate(
	bw_bd_reduce_coeffs * BW_RESTRICT coeffs,
	float                             sample_rate);

Sets the sample_rate (Hz) value in coeffs.

bw_bd_reduce_reset_coeffs()

static inline void bw_bd_reduce_reset_coeffs(
	bw_bd_reduce_coeffs * BW_RESTRICT coeffs);

Resets coefficients in coeffs to assume their target values.

bw_bd_reduce_update_coeffs_ctrl()

static inline void bw_bd_reduce_update_coeffs_ctrl(
	bw_bd_reduce_coeffs * BW_RESTRICT coeffs);

Triggers control-rate update of coefficients in coeffs.

bw_bd_reduce_update_coeffs_audio()

static inline void bw_bd_reduce_update_coeffs_audio(
	bw_bd_reduce_coeffs * BW_RESTRICT coeffs);

Triggers audio-rate update of coefficients in coeffs.

bw_bd_reduce_process1()

static inline float bw_bd_reduce_process1(
	const bw_bd_reduce_coeffs * BW_RESTRICT coeffs,
	float                                   x);

Processes one input sample x using coeffs. Returns the corresponding output sample.

bw_bd_reduce_process()

static inline void bw_bd_reduce_process(
	bw_bd_reduce_coeffs * BW_RESTRICT coeffs,
	const float *                     x,
	float *                           y,
	size_t                            n_samples);

Processes the first n_samples of the input buffer x and fills the first n_samples of the output buffer y, while using and updating coeffs (control and audio rate).

bw_bd_reduce_process_multi()

static inline void bw_bd_reduce_process_multi(
	bw_bd_reduce_coeffs * BW_RESTRICT coeffs,
	const float * const *             x,
	float * const *                   y,
	size_t                            n_channels,
	size_t                            n_samples);

Processes the first n_samples of the n_channels input buffers x and fills the first n_samples of the n_channels output buffers y, while using and updating the common coeffs (control and audio rate).

bw_bd_reduce_set_bit_depth()

static inline void bw_bd_reduce_set_bit_depth(
	bw_bd_reduce_coeffs * BW_RESTRICT coeffs,
	char                              value);

Sets the output bit depth value in coeffs.

Valid range: [1, 64].

Default value: 16.

bw_bd_reduce_set_silence_dc()

static inline void bw_bd_reduce_set_silence_dc(
	bw_bd_reduce_coeffs * BW_RESTRICT coeffs,
	char                              value);

Sets whether the output value corresponding to silence has null dc (value 0) or not (non-0) in coeffs.

Default value: non-0 (non-null dc).

bw_bd_reduce_set_gate_lin()

static inline void bw_bd_reduce_set_gate_lin(
	bw_bd_reduce_coeffs * BW_RESTRICT coeffs,
	float                             value);

Sets the input gate threshold value (linear) in coeffs.

Valid range: [0.f, 1.f].

Default value: 0.f.

bw_bd_reduce_set_gate_dBFS()

static inline void bw_bd_reduce_set_gate_dBFS(
	bw_bd_reduce_coeffs * BW_RESTRICT coeffs,
	float                             value);

Sets the input gate threshold value (dBFS) in coeffs.

Valid range: [-INFINITY, 0.f].

Default value: -INFINITY.

bw_bd_reduce_coeffs_is_valid()

static inline char bw_bd_reduce_coeffs_is_valid(
	const bw_bd_reduce_coeffs * BW_RESTRICT coeffs);

Tries to determine whether coeffs is valid and returns non-0 if it seems to be the case and 0 if it is certainly not. False positives are possible, false negatives are not.

coeffs must at least point to a readable memory block of size greater than or equal to that of bw_bd_reduce_coeffs.

C++ wrapper

Brickworks::BDReduce

template<size_t N_CHANNELS = 1>
class BDReduce {
public:
	BDReduce();

	void setSampleRate(
		float sampleRate);

	void reset();

	void process(
		const float * const * x,
		float * const *       y,
		size_t                nSamples);

# ifndef BW_CXX_NO_ARRAY
	void process(
		std::array<const float *, N_CHANNELS> x,
		std::array<float *, N_CHANNELS>       y,
		size_t                                nSamples);
# endif

	void setBitDepth(
		char value);

	void setSilenceDc(
		char value);

	void setGateLin(
		float value);

	void setGateDBFS(
		float value);
...
}

Changelog

• Version 1.2.1:
  • Added default value for N_CHANNELS in C++ API.
  • Updated dependencies.
• Version 1.2.0:
  • Added gate parameter.
  • Added support for BW_INCLUDE_WITH_QUOTES, BW_NO_CXX, and BW_CXX_NO_EXTERN_C.
  • Added debugging checks from bw_bd_reduce_process() to bw_bd_reduce_process_multi().
  • Added debugging checks in bw_bd_reduce_process_multi() to ensure that buffers used for both input and output appear at the same channel indices.
• Version 1.1.0:
  • Added silence_dc parameter.
  • Now using BW_NULL and BW_CXX_NO_ARRAY.
• Version 1.0.0:
  • Added bw_bd_reduce_set_sample_rate().
  • bw_bd_reduce_process() and bw_bd_reduce_process_multi() now use size_t to count samples and channels.
  • Added more const specifiers to input arguments.
  • Moved C++ code to C header.
  • Added overloaded C++ process() function taking C-style arrays as arguments.
  • Removed usage of reserved identifiers.
  • Clearly specified parameter validity ranges.
  • Added debugging code.
• Version 0.6.0:
  • Removed dependency on bw_config.
• Version 0.5.0:
  • Added bw_bd_reduce_process_multi().
  • Added C++ wrapper.
• Version 0.4.0:
  • Fixed unused parameter warnings.
• Version 0.3.0:
  • First release.