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,
        const char *device,
        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).
• device char * : String representation of the device (e.g., CPU or GPU) to use. If set to best, the most suitable device is selected automatically. If set to gpu, the engine uses the first available GPU device. To select a specific GPU device, set this argument to gpu:${GPU_INDEX}, where ${GPU_INDEX} is the index of the target GPU. If set to cpu, the engine will run on the CPU with the default number of threads. To specify the number of threads, set this argument to cpu:${NUM_THREADS}, where ${NUM_THREADS} is the desired number of threads.
• 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_cheetah_list_hardware_devices()

pv_status_t pv_cheetah_list_hardware_devices(
        char ***hardware_devices,
        int32_t *num_hardware_devices);

Gets a list of hardware devices that can be specified when calling pv_cheetah_init().

Parameters

• hardware_devices const char * * * : Array of available hardware devices. Devices are NULL terminated strings. The array must be freed using pv_cheetah_free_hardware_devices().
• num_hardware_devices int32_t * : The number of devices in the hardware_devices array.

Returns

• pv_status_t : Returned status code.

pv_cheetah_free_hardware_devices()

void pv_cheetah_free_hardware_devices(
        char ***hardware_devices,
        int32_t *num_hardware_devices);

This function frees the memory allocated by pv_cheetah_list_hardware_devices().

Parameters

• hardware_devices const char * * * : Array of available hardware devices allocated by pv_cheetah_list_hardware_devices().
• num_hardware_devices int32_t * : The number of devices in the hardware_devices array.

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.