OH_MIDIPortDescriptor

typedef struct {...} OH_MIDIPortDescriptor

Overview

This struct describes the port descriptor, which is used to specify the port index and protocol behavior for opening a port.

Since: 24

Related module: OHMIDI

Header file: native_midi_base.h

Summary

Member Variables

Name	Description
uint32_t portIndex	Index of the port to be opened. Since: 24
OH_MIDIProtocol protocol	MIDI protocol version to be used (MIDI 1.0 or MIDI 2.0). The service converts data between applications and hardware based on the value of this field. An application merely declares the expected protocol version. The following system behavior applies when the protocol version does not match the hardware: 1. Requesting OH_MIDI_PROTOCOL_1.0 on a MIDI 2.0 device (lossless compatibility): The application sends UMP Type 2 (MIDI 1.0 channel voice) messages. The service forwards them directly to the device. No data loss occurs. 2. Requesting OH_MIDI_PROTOCOL_2.0 on a MIDI 1.0 device (lossy conversion): The application sends UMP Type 4 (MIDI 2.0 channel voice) messages. The service down-converts them to Type 2 messages (for example, truncating velocity values and discarding per-note data). Data precision is lost, and advanced messages may be discarded. Since: 24

Name

Description

uint32_t portIndex

Index of the port to be opened.
Since: 24

OH_MIDIProtocol protocol

MIDI protocol version to be used (MIDI 1.0 or MIDI 2.0). The service converts data between applications and hardware based on the value of this field. An application merely declares the expected protocol version. The following system behavior applies when the protocol version does not match the hardware:
1. Requesting OH_MIDI_PROTOCOL_1.0 on a MIDI 2.0 device (lossless compatibility):
The application sends UMP Type 2 (MIDI 1.0 channel voice) messages. The service forwards them directly to the device. No data loss occurs.
2. Requesting OH_MIDI_PROTOCOL_2.0 on a MIDI 1.0 device (lossy conversion):
The application sends UMP Type 4 (MIDI 2.0 channel voice) messages. The service down-converts them to Type 2 messages (for example, truncating velocity values and discarding per-note data). Data precision is lost, and advanced messages may be discarded.
Since: 24