Cheetah Speech-to-Text
C API

API Reference for the Cheetah C SDK.

pv_cheetah_t

typedef struct pv_cheetah pv_cheetah_t;

Container representing the Cheetah Speech-to-Text engine.

pv_cheetah_init()

pv_status_t pv_cheetah_init(
        const char *access_key,
        const char *model_path,
        float endpoint_duration_sec,
        bool enable_automatic_punctuation,
        pv_cheetah_t **object);

Creates a Cheetah instance. Resources should be cleaned when you are done using the pv_cheetah_delete() function.

Parameters

• access_key const char * : AccessKey obtained from Picovoice Console.
• model_path const char * : Absolute path to the file containing model parameters (.pv).
• endpoint_duration float : Duration of endpoint in seconds. A speech endpoint is detected when there is a segment of audio (with a duration specified herein) after an utterance without any speech in it. Set to 0 to disable endpoint detection.
• enable_automatic_punctuation bool : Set to true to enable automatic punctuation insertion.
• object pv_cheetah_t * * : Constructed instance of Cheetah.

Returns

• pv_status_t : Status code.

pv_cheetah_delete()

void pv_cheetah_delete(pv_cheetah_t *object);

Releases resources acquired by Cheetah.

Parameters

• object pv_cheetah_t * : Picovoice object.

pv_cheetah_process()

pv_status_t pv_cheetah_process(
    pv_cheetah_t *object,
    const int16_t *pcm,
    char **transcript,
    bool *is_endpoint);

Processes a frame of audio and returns newly-transcribed text and a flag indicating if an endpoint has been detected. Upon detection of an endpoint, the client may invoke pv_cheetah_flush() to retrieve any remaining transcription. The caller is responsible for freeing the transcription buffer.

The number of samples per frame can be attained by calling pv_cheetah_frame_length(). The incoming audio needs to have a sample rate equal to pv_sample_rate() and be 16-bit linearly-encoded. Cheetah operates on single-channel audio.

Parameters

• object pv_cheetah_t * : Cheetah object.
• pcm int16_t : A frame of audio samples.
• transcript char * * : Inferred transcription.
• is_endpoint bool * : Flag indicating if an endpoint has been detected. If endpoint is disabled then set to NULL.

Returns

• pv_status_t : Status code.

pv_cheetah_flush()

pv_status_t pv_cheetah_flush(pv_cheetah_t *object, char **transcript);

Marks the end of the audio stream, flushes internal state of the object, and returns any remaining transcript. The caller is responsible for freeing the transcription buffer.

Parameters

• object pv_cheetah_t * : Cheetah object.
• transcript char * * : Inferred transcription.

Returns

• pv_status_t : Status code.

pv_cheetah_transcript_delete()

void pv_cheetah_transcript_delete(char *transcript);

Deletes transcript returned from pv_cheetah_process or pv_cheetah_flush.

Parameters

• transcript char * : Transcript returned by Cheetah.

pv_cheetah_version()

const char *pv_cheetah_version(void);

Getter for version.

Returns

• const char * : Cheetah version.

pv_cheetah_frame_length()

int32_t pv_cheetah_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 Cheetah.

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

• status int32_t : Status code.

Returns

• const char * : String representation of status code.

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.

Returns

• pv_status_t : Returned status code.

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.