Leopard Speech-to-Text
C API

API Reference for the Leopard C SDK.

pv_leopard_t

typedef struct pv_leopard pv_leopard_t;

Container representing the Leopard Speech-to-Text engine.

pv_leopard_init()

pv_status_t pv_leopard_init(
        const char *access_key,
        const char *model_path,
        bool enable_automatic_punctuation,
        bool enable_diarization,
        pv_leopard_t **object);

Creates a Leopard instance. Resources should be cleaned when you are done using the pv_leopard_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).
• enable_automatic_punctuation bool : Set to true to enable automatic punctuation insertion.
• enable_diarization bool: Set to true to enable speaker diarization, which allows Leopard to differentiate speakers as part of the transcription process. Word metadata will include a speaker_tag to identify unique speakers.
• object pv_leopard_t * * : Constructed instance of Leopard.

Returns

• pv_status_t : Status code.

pv_leopard_delete()

void pv_leopard_delete(pv_leopard_t *object);

Releases resources acquired by Leopard.

Parameters

• object pv_leopard_t * : Picovoice object.

pv_leopard_process()

pv_status_t pv_leopard_process(
    pv_leopard_t *object,
    const int16_t *pcm,
    int32_t num_samples,
    char **transcript,
    int32_t *num_words,
    pv_word_t **words);

Processes a given audio data and returns its transcription. The caller is responsible for freeing the transcript and words buffers using pv_leopard_transcript_delete() and pv_leopard_words_delete(), respectively. The audio needs to have a sample rate equal to pv_sample_rate() and be 16-bit linearly-encoded. This function operates on single-channel audio.

Parameters

• object pv_leopard_t * : Leopard object.
• pcm int16_t : A frame of audio samples.
• num_samples int32_t : Number of audio samples to process.
• transcript char * * : Inferred transcription.
• num_words int32_t * : Number of transcribed words.
• words pv_word_t * * : Transcribed words and their associated metadata.

Returns

• pv_status_t : Status code.

pv_leopard_process_file()

pv_status_t pv_leopard_process_file(
    pv_leopard_t *object,
    const char *audio_path,
    char **transcript,
    int32_t *num_words,
    pv_word_t **words);

Processes a given audio file and returns its transcription. The caller is responsible for freeing the transcript and words buffers using pv_leopard_transcript_delete() and pv_leopard_words_delete(), respectively. The supported formats are: 3gp (AMR), FLAC, MP3, MP4/m4a (AAC), Ogg, WAV and WebM.

Parameters

• object pv_leopard_t * : Leopard object.
• audio_path const char * : Absolute path to the audio file.
• transcript char * * : Inferred transcription.
• num_words int32_t * : Number of transcribed words.
• words pv_word_t * * : Transcribed words and their associated metadata.

Returns

• pv_status_t : Status code.

pv_leopard_transcript_delete()

void pv_leopard_transcript_delete(char *transcript);

Deletes transcript returned from pv_leopard_process() or pv_leopard_process_file().

Parameters

• transcript char * : transcription string returned from pv_leopard_process() or pv_leopard_process_file().

pv_leopard_words_delete()

void pv_leopard_words_delete(pv_word_t *words);

Deletes words returned from pv_leopard_process() or pv_leopard_process_file().

Parameters

• words pv_word_t * * : transcribed words returned from pv_leopard_process() or pv_leopard_process_file().

pv_leopard_version()

const char *pv_leopard_version(void);

Getter for version.

Returns

• const char * : Leopard version.

pv_sample_rate()

int32_t pv_sample_rate(void);

Audio sample rate accepted by Leopard.

Returns

• int32_t : Sample rate.

pv_word_t

typedef struct {
    const char *word; /** Transcribed word. */
    float start_sec; /** Start of word in seconds. */
    float end_sec; /** End of word in seconds. */
    float confidence; /** Transcription confidence. It is a number within [0, 1]. */
    int32_t speaker_tag; /** The speaker tag is `-1` if diarization is not enabled during initialization;
                          * otherwise, it's a non-negative integer identifying unique speakers, with `0` reserved for
                          * unknown speakers.
                          */
} pv_word_t;

Struct for a transcribed word and its associated metadata.

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.