Porcupine Wake Word
Microcontroller API

This document outlines how to use the Porcupine wake word engine on a microcontroller.

pv_porcupine_t

typedef struct pv_porcupine pv_porcupine_t;

Container representing the Porcupine wake word engine.

pv_porcupine_init()

pv_status_t pv_porcupine_init(
        const char *access_key,
        int32_t memory_size,
        void *memory_buffer,
        int32_t num_keywords,
        const int32_t *keyword_model_sizes,
        const void *const *keyword_models,
        const float *sensitivities,
        pv_porcupine_t **object
);

Create a Porcupine instance. Resources should be cleaned when you are done using the pv_porcupine_delete() function.

Parameters

• access_key char * : AccessKey obtained from Picovoice Console (https://console.picovoice.ai/).
• memory_size int32_t : Memory size in bytes. The optimal size for given keyword models can be computed using pv_porcupine_get_min_memory_buffer_size()
• memory_buffer void * : Memory; needs to be 8-byte aligned.
• num_keywords int32_t : Number of keywords to monitor.
• keyword_model_size int32_t * : Size of each keyword model in bytes.
• keyword_model void * * : Keyword models.
• sensitivities float * : Sensitivities for detecting keywords. Each value should be a number within [0, 1]. A higher sensitivity results in fewer misses at the cost of increasing the false alarm rate.
• object pv_porcupine_t * * : Constructed instance of Porcupine.

Returns

• pv_status_t : Returned status code.

pv_porcupine_get_min_memory_buffer_size()

pv_status_t pv_porcupine_get_min_memory_buffer_size(
        int32_t preliminary_memory_size,
        void *preliminary_memory_buffer,
        int32_t num_keywords,
        const int32_t *keyword_model_sizes,
        const void *const *keyword_models,
        int32_t *min_memory_buffer_size
);

Computes the minimum required memory buffer size, in bytes, for the given keyword model. A relatively large value for ' preliminary_memory_buffer' is suggested (e.g., 30 kilobytes). Then, 'pv_porcupine_init' can be called optimally passing a memory buffer with the size of 'min_memory_buffer_size'.

Parameters

• preliminary_memory_size int32_t : Memory size in bytes.
• preliminary_memory_buffer void * : Memory; needs to be 8-byte aligned.
• num_keywords int32_t : Number of keywords to monitor.
• keyword_model_size int32_t * : Size of each keyword model in bytes.
• keyword_model void * * : Keyword models.
• min_memory_buffer_size int32_t * : minimum required memory buffer size in bytes.

Returns

• pv_status_t : Returned status code.

pv_porcupine_delete()

void pv_porcupine_delete(pv_porcupine_t *object);

Releases resources acquired by Porcupine.

Parameters

• object pv_porcupine_t * : Porcupine object.

pv_porcupine_process()

pv_status_t pv_porcupine_process(pv_porcupine_t *object, const int16_t *pcm, int32_t *keyword_index);

Processes a frame of the incoming audio stream and emits the detection result. The number of samples per frame can be attained by calling pv_porcupine_frame_length(). The incoming audio needs to have a sample rate equal to pv_sample_rate() and be 16-bit linearly-encoded. Porcupine operates on single-channel audio.

Parameters

• object pv_porcupine_t * : Porcupine object.
• pcm int16_t : A frame of audio samples.
• keyword_index int32_t * : Index of observed keyword at the end of the current frame. Indexing is 0-based and matches the ordering of keyword models provided to 'pv_porcupine_init()'. If no keyword is detected then it is set to -1.

Returns

• pv_status_t : Returned status code.

pv_porcupine_version()

const char *pv_porcupine_version(void);

Getter for version.

Returns

• char * : Porcupine version.

pv_porcupine_frame_length()

int32_t pv_picovoice_frame_length(void);

Getter for number of audio samples per frame.

Returns

• int32_t : Frame length.

pv_sample_rate()

int32_t pv_sample_rate(void);

Audio sample rate accepted by Picovoice.

Returns

• int32_t : Sample rate.

pv_status_t

typedef enum {
    PV_STATUS_SUCCESS = 0,
    PV_STATUS_OUT_OF_MEMORY,
    PV_STATUS_IO_ERROR,
    PV_STATUS_INVALID_ARGUMENT,
    PV_STATUS_STOP_ITERATION,
    PV_STATUS_KEY_ERROR,
    PV_STATUS_INVALID_STATE,
    PV_STATUS_RUNTIME_ERROR,
    PV_STATUS_ACTIVATION_ERROR,
    PV_STATUS_ACTIVATION_LIMIT_REACHED,
    PV_STATUS_ACTIVATION_THROTTLED,
    PV_STATUS_ACTIVATION_REFUSED
} pv_status_t;

Status code enum.

pv_status_to_string()

const char *pv_status_to_string(pv_status_t status);

Parameters

• int32_t : Returned status code.

Returns

• char * : String representation.

pv_get_error_stack()

pv_status_t pv_get_error_stack(
        char ***message_stack,
        int32_t *message_stack_depth);

If a function returns a failure (any pv_status_t other than PV_STATUS_SUCCESS), this function can be called to get a series of error messages related to the failure. This function can only be called only once per failure status on another function. The memory for message_stack must be freed using pv_free_error_stack.

Regardless of the return status of this function, if message_stack is not NULL, then message_stack contains valid memory. However, a failure status on this function indicates that future error messages may not be reported.

Parameters

• message_stack const char * * * : Array of messages relating to the failure. Messages are NULL terminated strings. The array and messages must be freed using pv_free_error_stack().
• message_stack_depth int32_t * : The number of messages in the message_stack array.

pv_free_error_stack()

void pv_free_error_stack(char **message_stack);

This function frees the memory used by error messages allocated by pv_get_error_stack().

Parameters

• message_stack const char * * * : Array of messages relating to the failure.