scamp.playback_implementations.PlaybackImplementation

class scamp.playback_implementations.PlaybackImplementation(*args, **kwargs)

Bases: expenvelope.json_serializer.SavesToJSON

Abstract base class for playback implementations, which do the actual work of playback, either by playing sounds or by sending messages to external synthesizers to play sounds.

Parameters

host_instrument – The ScampInstrument that will use this playback implementation for playback. When this PlaybackImplementation is constructed, it is automatically added to the list of PlaybackImplementations that the host instrument uses.

Methods

change_note_parameter(note_id, …)	Method that implements the change of a parameter other than pitch or volume
change_note_pitch(note_id, new_pitch)	Method that implements the change of a note’s pitch
change_note_volume(note_id, new_volume)	Method that implements the change of a note’s volume
end_note(note_id)	Method that implements the end of a note
get_shared_resource(key)	Gets the shared resource for this type of playback implementation under the given key.
has_shared_resource(key)	Checks whether there is a shared resource for this type of playback implementation under the given key.
set_host_instrument(host_instrument)	Sets the host instrument for this PlaybackImplementation.
set_max_pitch_bend(semitones)	Method that sets the max pitch bend for MIDI-based playback implementations This is only relevant when playback is happening via the MIDI protocol.
set_shared_resource(key, value)	Sets a shared resource for this type of playback implementation under the given key.
start_note(note_id, pitch, volume, properties)	Method that implements the start of a note

Inherited Methods

duplicate()	Returns a copy of this object by serializing to and from JSON.
json_dumps()	Dump this object as a JSON string.
json_loads(s)	Load this object from a JSON string.
load_from_json(file_path)	Load this object from a JSON file with the given path.
save_to_json(file_path)	Save this object to a JSON file using the given path.

Attributes

resource_dictionary

Dictionary of shared resources for this type of playback implementation.

set_host_instrument(host_instrument: scamp.instruments.ScampInstrument)

Sets the host instrument for this PlaybackImplementation. Ordinarily, the host instrument is supplied as an argument to the __init__ method, which then automatically calls this method. However, it is also possible to pass the value None to the host instrument argument initially and later set it with this method.

Parameters

host_instrument – The ScampInstrument that will use this playback implementation for playback. This PlaybackImplementation will be added to the host instrument’s playback_implementations attribute.

property resource_dictionary

Dictionary of shared resources for this type of playback implementation. For instance, SoundfontPlaybackImplementation uses this to store an instance of SoundfontHost. Only one instance of fluidsynth (and therefore SoundfontHost) needs to be running for all instruments in the ensemble, so this is a way of pooling that resource.

has_shared_resource(key) → bool

Checks whether there is a shared resource for this type of playback implementation under the given key.

Parameters

key – key name for this resource

get_shared_resource(key)

Gets the shared resource for this type of playback implementation under the given key.

Parameters

key – key name for this resource

set_shared_resource(key, value)

Sets a shared resource for this type of playback implementation under the given key.

Parameters

• key – key name for this resource

• value – value to set for that key

abstract start_note(note_id: int, pitch: float, volume: float, properties: dict, other_parameter_values: dict = None) → None

Method that implements the start of a note

Parameters

• note_id – unique identifier for the note we are starting

• pitch – floating-point MIDI pitch value

• volume – floating-point volume value (from 0 to 1)

• properties – a NotePropertiesDictionary

• other_parameter_values – dictionary mapping parameter name to parameter value for parameters other than pitch and volume. (This information was extracted from the properties dictionary.)

abstract end_note(note_id: int) → None

Method that implements the end of a note

Parameters

note_id – unique identifier of the note to end

abstract change_note_pitch(note_id: int, new_pitch: float) → None

Method that implements the change of a note’s pitch

Parameters

• note_id – unique identifier of the note whose pitch to change

• new_pitch – new (floating-point) MIDI pitch value

abstract change_note_volume(note_id: int, new_volume: float) → None

Method that implements the change of a note’s volume

Parameters

• note_id – unique identifier of the note whose volume to change

• new_volume – new floating point volume value from 0 to 1

abstract change_note_parameter(note_id: int, parameter_name: str, new_value: float) → None

Method that implements the change of a parameter other than pitch or volume

Parameters

• note_id – unique identifier of the note to effect

• parameter_name – name of the parameter to change

• new_value – new floating-point value of that parameter

abstract set_max_pitch_bend(semitones: int) → None

Method that sets the max pitch bend for MIDI-based playback implementations This is only relevant when playback is happening via the MIDI protocol.

Parameters

semitones – unique identifier of the note to effect

duplicate() → T

Returns a copy of this object by serializing to and from JSON.

json_dumps() → str

Dump this object as a JSON string. This uses a custom encoder that recognizes and appropriately converts any attributes that are object inheriting from SavesToJSON.

classmethod json_loads(s: str) → T

Load this object from a JSON string. This uses a custom decoder that looks for a “_type” key in any object/dictionary being parsed and converts it to the class specified (assuming it a subclass of SavesToJSON).

Parameters

s – a string representing this object in JSON format

classmethod load_from_json(file_path: str) → T

Load this object from a JSON file with the given path. This uses a custom decoder that looks for a “_type” key in any object/dictionary being parsed and converts it to the class specified (assuming it a subclass of SavesToJSON).

Parameters

file_path – path for loading the file

save_to_json(file_path: str) → None

Save this object to a JSON file using the given path. This uses a custom encoder that recognizes and appropriately converts any attributes that are object inheriting from SavesToJSON.

Parameters

file_path – path for saving the file