Koala Noise Suppression
C API

API Reference for the Koala C SDK.

pv_koala_t

typedef struct pv_koala pv_koala_t;

Container representing the Koala Noise Suppression engine.

pv_koala_init()

pv_status_t pv_koala_init(
    const char *access_key,
    const char *model_path,
    const char *device,
    pv_koala_t **object);

Creates a Koala instance. Resources should be cleaned when you are done using the pv_koala_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.
• object pv_koala_t * * : Constructed instance of Koala.

Returns

• pv_status_t : Status code.

pv_koala_delete()

void pv_koala_delete(pv_koala_t *object);

Releases resources acquired by Koala.

Parameters

• object pv_koala_t * : Koala object.

pv_koala_process()

pv_status_t pv_koala_process(
    pv_koala_t *object,
    const int16_t *pcm,
    int16_t *enhanced_pcm);

Processes a frame of the incoming audio stream and returns a frame of enhanced audio. The output is not necessarily in sync with the input frame; instead, the output audio will contain the enhancement result for audio that has been passed to previous calls of this function. The total delay in samples can be obtained by pv_koala_delay_sample(). The number of samples per frame can be attained by calling pv_koala_frame_length(). The incoming audio needs to have a sample rate equal to pv_sample_rate() and be 16-bit linearly-encoded. Koala operates on single-channel audio.

Parameters

• object pv_koala_t * : Koala object.
• pcm int16_t : A frame of audio samples.
• enhanced_pcm int16_t : A frame of enhanced audio samples. Needs to point to an allocated block of memory of the same size as the pcm input argument.

Returns

• pv_status_t : Status code.

pv_koala_reset()

pv_status_t pv_koala_reset(pv_koala_t *object);

Finalizes the enhancement process and resets the internal state of the Koala object. Subsequent calls to pv_koala_process() will not return any delayed samples from previous calls; that data will be lost. Instead, the result will be the same as if the Koala object were newly created.

Parameters

• object pv_koala_t * : Koala object.

Returns

• pv_status_t : Status code.

pv_koala_delay_sample()

pv_status_t pv_koala_delay_sample(
    const pv_koala_t *object, 
    int32_t *delay_sample);

Getter for the delay in samples. If the input and output of sequential calls to pv_koala_process are viewed as two contiguous streams of audio data, this delay specifies the time shift between the input and output stream.

Parameters

• object pv_koala_t * : Koala object.
• delay_sample int32_t * : Delay in samples.

Returns

• pv_status_t : Status code.

pv_koala_frame_length()

int32_t pv_koala_frame_length(void);

Getter for number of audio samples per frame.

Returns

• int32_t : Frame length.

pv_koala_version()

const char *pv_koala_version(void);

Getter for version.

Returns

• const char * : Koala version.

pv_sample_rate()

int32_t pv_sample_rate(void);

Audio sample rate accepted by Koala.

Returns

• int32_t : Sample rate.

pv_koala_list_hardware_devices()

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

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

Parameters

• hardware_devices const char * * * : Array of available hardware devices. Devices are NULL terminated strings. The array must be freed using pv_koala_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_koala_free_hardware_devices()

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

This function frees the memory allocated by pv_koala_list_hardware_devices().

Parameters

• hardware_devices const char * * * : Array of available hardware devices allocated by pv_koala_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.