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Media Trigger API

Media Trigger is used for Voice Trigger scenarios, enabling keyword detection and recognition through loading acoustic models.

Header: #include <media_trigger.h>

openvela Implementation Notes

• Typical Scenarios: Voice wake-up on smart speakers, smartwatches, etc.
• Workflow:
  1. open to open a trigger handle
  2. set_event_callback to register an event callback
  3. load_sound_model to load an acoustic model
  4. start_recognition to start recognition
  5. Listen for callbacks and process when a keyword is detected
  6. stop_recognition → unload_sound_model → close for cleanup
• Parameter Configuration: The params passed to open selects the microphone configuration (e.g. "default" / "Dual Mic")
• Underlying Implementation: Interfaces with the DSP-side acoustic model processor

Trigger Lifecycle

media_trigger_open

void* media_trigger_open(const char* params);

Opens a media trigger handle.

Parameters:

• params Trigger parameter string, e.g. "default" or "Dual Mic", used to select the microphone configuration.

Returns:

Returns the trigger handle on success, or NULL on failure.

Example:

// 1. Create instance
void* handle = media_trigger_open("default");

// 2. Set event callback
ret = media_trigger_set_event_callback(handle, cookie, callback);

// 3. Load acoustic model
ret = media_trigger_load_sound_model(handle, model, model_size);

// 4. Start recognition
ret = media_trigger_start_recognition(handle);

// 5. Stop recognition
ret = media_trigger_stop_recognition(handle);

// 6. Unload model
ret = media_trigger_unload_sound_model(handle);

// 7. Close handle
ret = media_trigger_close(handle);

media_trigger_close

int media_trigger_close(void* handle);

Closes the trigger handle and releases associated resources.

Parameters:

• handle The trigger handle to close.

Returns:

Returns 0 on success, or a negative errno on failure.

Events and Callbacks

media_trigger_set_event_callback

int media_trigger_set_event_callback(void* handle, void* event_cookie,
                                     media_event_callback on_event);

Sets an event callback for the trigger to receive events such as recognition state changes.

Parameters:

• handle Trigger handle.
• event_cookie User data passed to the callback.
• on_event Event callback function.

Returns:

Returns 0 on success, or a negative errno on failure.

Acoustic Model Management

media_trigger_load_sound_model

int media_trigger_load_sound_model(void* handle, void* model, size_t model_size);

Loads acoustic model data for the trigger.

Parameters:

• handle Trigger handle.
• model Pointer to acoustic model data.
• model_size Size of the model data in bytes.

Returns:

Returns 0 on success, or a negative errno on failure.

media_trigger_unload_sound_model

int media_trigger_unload_sound_model(void* handle);

Unloads the currently loaded acoustic model.

Parameters:

• handle Trigger handle.

Returns:

Returns 0 on success, or a negative errno on failure.

Recognition Control

media_trigger_start_recognition

int media_trigger_start_recognition(void* handle);

Starts voice recognition. The trigger continuously detects input audio and matches keywords in the loaded model.

Parameters:

• handle Trigger handle.

Returns:

Returns 0 on success, or a negative errno on failure.

media_trigger_stop_recognition

int media_trigger_stop_recognition(void* handle);

Stops voice recognition.

Parameters:

• handle Trigger handle.

Returns:

Returns 0 on success, or a negative errno on failure.

DSP Property Query

media_trigger_get_property

int media_trigger_get_property(char* properties, int len);

Queries property information of the underlying DSP for the trigger.

Parameters:

• properties Output buffer for receiving the property string.
• len Buffer length.

Returns:

Returns 0 on success, or a negative errno on failure.