C API Reference

Plugin Functions (minihost.h)

Function	Description
mh_open	Load a plugin
mh_open_ex	Load a plugin with sidechain channel configuration
mh_open_async	Load a plugin in a background thread
mh_close	Unload a plugin
mh_get_info	Get plugin info (channels, params, latency, MIDI capabilities)
mh_probe	Get plugin metadata without full instantiation
mh_scan_directory	Recursively scan directory for plugins

Audio Processing

Function	Description
mh_process	Process audio (non-interleaved float32 buffers)
mh_process_midi	Process audio with MIDI input
mh_process_midi_io	Process audio with MIDI input and output
mh_process_auto	Process with sample-accurate parameter automation and MIDI
mh_process_sidechain	Process audio with sidechain input
mh_process_double	Process audio with 64-bit double precision
mh_supports_double	Check if plugin supports native double precision

Parameters

Function	Description
mh_get_num_params	Get parameter count
mh_get_param	Get parameter value (normalized 0.0-1.0)
mh_set_param	Set parameter value (normalized 0.0-1.0)
mh_get_param_info	Get parameter metadata (name, label, default, steps, ID, category)
mh_param_to_text	Convert normalized value to display string (e.g., "2500 Hz")
mh_param_from_text	Convert display string to normalized value
mh_begin_param_gesture	Signal start of parameter change gesture
mh_end_param_gesture	Signal end of parameter change gesture

State Management

Function	Description
mh_get_state_size	Get full state size in bytes
mh_get_state	Save full plugin state
mh_set_state	Restore full plugin state
mh_get_program_state_size	Get current program state size
mh_get_program_state	Save current program state
mh_set_program_state	Restore current program state

Factory Presets

Function	Description
mh_get_num_programs	Get number of factory presets
mh_get_program_name	Get preset name by index
mh_get_program	Get current preset index
mh_set_program	Load preset by index

Transport and Playback

Function	Description
mh_set_transport	Set transport info (BPM, time signature, position, play state)
mh_get_bypass	Get bypass state
mh_set_bypass	Set bypass state
mh_reset	Reset internal state (clears delay lines, filter states)
mh_set_non_realtime	Enable higher-quality algorithms for offline processing

Configuration

Function	Description
mh_get_sample_rate	Get current sample rate
mh_set_sample_rate	Change sample rate (preserves parameter state)
mh_get_latency_samples	Get plugin latency in samples
mh_get_tail_seconds	Get reverb/delay tail length in seconds
mh_get_processing_precision	Get processing precision (single/double)
mh_set_processing_precision	Set processing precision (single/double)
mh_set_track_properties	Set track name and/or color metadata

Bus Layout

Function	Description
mh_get_num_buses	Get number of input or output buses
mh_get_bus_info	Get bus info (name, channels, is_main, is_enabled)
mh_check_buses_layout	Check if a bus layout is supported
mh_get_sidechain_channels	Get configured sidechain channel count

Change Notifications

Function	Description
mh_set_change_callback	Register callback for processor-level changes (latency, param info, program, non-param state)
mh_set_param_value_callback	Register callback for plugin-initiated parameter value changes
mh_set_param_gesture_callback	Register callback for parameter gesture begin/end

Constants: MH_CHANGE_LATENCY, MH_CHANGE_PARAM_INFO, MH_CHANGE_PROGRAM, MH_CHANGE_NON_PARAM_STATE

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Audio Device Functions (minihost_audio.h)

Function	Description
mh_audio_open	Open audio device for real-time plugin playback
mh_audio_open_chain	Open audio device for real-time chain playback
mh_audio_close	Close audio device
mh_audio_start	Start audio playback
mh_audio_stop	Stop audio playback
mh_audio_is_playing	Check if audio is currently playing
mh_audio_set_input_callback	Set input audio callback for effect plugins
mh_audio_get_sample_rate	Get actual device sample rate
mh_audio_get_buffer_frames	Get actual buffer size in frames
mh_audio_get_channels	Get number of output channels

Set MH_AudioConfig.capture = 1 to open the device in duplex mode (system audio input routed through the plugin). The audio callback de-interleaves captured audio directly into the plugin's input buffers.

Audio Input (Ring Buffer)

Function	Description
mh_audio_enable_input	Enable ring buffer audio input with given capacity
mh_audio_disable_input	Disable ring buffer input (revert to silence)
mh_audio_write_input	Write interleaved float32 frames into input ring buffer (thread-safe)
mh_audio_input_available	Get number of frames available for reading

MIDI Connections

Function	Description
mh_audio_connect_midi_input	Connect MIDI input port to device
mh_audio_connect_midi_output	Connect MIDI output port to device
mh_audio_disconnect_midi_input	Disconnect MIDI input
mh_audio_disconnect_midi_output	Disconnect MIDI output
mh_audio_get_midi_input_port	Get connected MIDI input port index (-1 if none)
mh_audio_get_midi_output_port	Get connected MIDI output port index (-1 if none)
mh_audio_create_virtual_midi_input	Create virtual MIDI input port
mh_audio_create_virtual_midi_output	Create virtual MIDI output port
mh_audio_is_midi_input_virtual	Check if MIDI input is a virtual port
mh_audio_is_midi_output_virtual	Check if MIDI output is a virtual port
mh_audio_send_midi	Send MIDI event programmatically to plugin

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Audio File I/O Functions (minihost_audiofile.h)

Function	Description
mh_audio_read	Read audio file to interleaved float32 buffer
mh_audio_data_free	Free decoded audio data returned by mh_audio_read
mh_audio_write	Write interleaved float32 data to WAV or FLAC file
mh_audio_get_file_info	Get audio file metadata without decoding
mh_audio_resample	Resample interleaved float32 audio between any two sample rates

Supported Formats

Format	Read	Write
WAV	Yes	Yes (16/24/32-bit)
FLAC	Yes	Yes (16/24-bit)
MP3	Yes	No
Vorbis	Yes	No

Structs

MH_AudioData -- returned by mh_audio_read(): - float* data -- interleaved float32 samples - unsigned int channels - unsigned int frames - unsigned int sample_rate

MH_AudioFileInfo -- populated by mh_audio_get_file_info(): - unsigned int channels - unsigned int sample_rate - unsigned long long frames - double duration

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Plugin Chain Functions (minihost_chain.h)

Function	Description
mh_chain_create	Create chain from array of plugins (all must share sample rate)
mh_chain_close	Close chain (does not close individual plugins)
mh_chain_process	Process audio through chain
mh_chain_process_midi_io	Process with MIDI I/O (MIDI goes to first plugin)
mh_chain_process_auto	Process with sample-accurate parameter automation and MIDI
mh_chain_get_latency_samples	Get total chain latency (sum of all plugins)
mh_chain_get_num_plugins	Get number of plugins in chain
mh_chain_get_plugin	Get plugin by index
mh_chain_get_num_input_channels	Get input channel count (from first plugin)
mh_chain_get_num_output_channels	Get output channel count (from last plugin)
mh_chain_get_sample_rate	Get sample rate (shared by all plugins)
mh_chain_get_max_block_size	Get maximum block size
mh_chain_reset	Reset all plugins in chain
mh_chain_set_non_realtime	Set non-realtime mode for all plugins
mh_chain_get_tail_seconds	Get maximum tail length (max of all plugins)

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MIDI Functions (minihost_midi.h)

Port Enumeration

Function	Description
mh_midi_get_num_inputs	Get number of available MIDI input ports
mh_midi_get_num_outputs	Get number of available MIDI output ports
mh_midi_get_input_name	Get MIDI input port name by index
mh_midi_get_output_name	Get MIDI output port name by index
mh_midi_enumerate_inputs	Enumerate input ports via callback
mh_midi_enumerate_outputs	Enumerate output ports via callback

Standalone MIDI I/O

Function	Description
mh_midi_in_open	Open MIDI input port with message callback
mh_midi_in_open_virtual	Create virtual MIDI input port with callback
mh_midi_in_close	Close MIDI input
mh_midi_out_open	Open MIDI output port
mh_midi_out_open_virtual	Create virtual MIDI output port
mh_midi_out_close	Close MIDI output
mh_midi_out_send	Send raw MIDI message on output port