Rhino - C API

Speech-to-Intent Engine
Domain Specific NLU
Offline SLU
Local Voice Recognition
Raspberry Pi
ARM Linux
iOS
Linux
Mac
Windows
C

This document outlines how to use the Rhino Speech-to-Intent engine within a C/C++ application.

Prerequisites

Rhino is implemented in ANSI C and is shipped as a precompiled library accompanied by corresponding header files. To integrate within a C/C++ application the following items are needed

Precompiled library for your target platform (e.g. Ubuntu x86_64 or Raspberry Pi 4)
Header files
The model file. The standard model is freely available on Rhino's GitHub repository. Enterprises who are commercially engaged with Picovoice can access compressed and standard models as well.
Context model file for your use case. A set of freely-available context files can be found on Rhino's GitHub repository. Enterprises who are engaged with Picovoice can create custom NLU models using Picovoice Console.

Integration

Rhino is implemented in ANSI C and therefore can be directly linked to C applications. Its header file contains relevant information. An instance of the Rhino object can be constructed as follows.

const char *model_file_path = ...
const char *context_file_path = ...
pv_rhino_t *rhino;
const pv_status_t status = pv_rhino_init(
    model_file_path,
    context_file_path,
    &rhino);
if (status != PV_STATUS_SUCCESS) {
    // add error handling code
}

Now the handle rhino can be used to infer intent from an incoming audio stream. Rhino accepts single channel, 16-bit PCM audio. The sample rate can be retrieved using pv_sample_rate(). Finally, Rhino accepts input audio in consecutive chunks (frames); the length of each frame can be retrieved using pv_rhino_frame_length().

extern const int16_t *get_next_audio_frame(void);
while (true) {
    const int16_t *pcm = get_next_audio_frame();
    bool is_finalized;
    pv_status_t status = pv_rhino_process(rhino, pcm, &is_finalized);
    if (status != PV_STATUS_SUCCESS) {
        // add error handling code
    }
    if (is_finalized) {
        bool is_understood;
        status = pv_rhino_is_understood(rhino, &is_understood);
        if (status != PV_STATUS_SUCCESS) {
            // add error handling code
        }
        if (is_understood) {
            const char *intent;
            int num_slots;
            const char **slots;
            const char **values;
            status = pv_rhino_get_intent(
                rhino,
                &intent,
                &num_slots,
                &slots,
                &values);
            if (status != PV_STATUS_SUCCESS) {
                // add error handling code
            }
            // add code to take action based on inferred intent and slot values
            pv_rhino_free_slots_and_values(rhino, slots, values);
        } else {
            // add code to handle unsupported commands
        }
        pv_rhino_reset(rhino);
    }
}

When done, remember to release the resources acquired.

pv_rhino_delete(rhino);