Audio Recording
C Quick Start

Platforms

• Linux (x86_64)
• macOS (x86_64, arm64)
• Windows (x86_64, arm64)
• Raspberry Pi (Zero, 3, 4, 5)

Requirements

• CMake 3.4+.
• C99 compatible compiler.
• Windows: MinGW.

Quick Start

Setup

Include the public header files (pv_recorder.h and pv_circular_buffer.h).

Usage

1. Create a PvRecorder object:

#include "pv_recorder.h"

const int32_t frame_length = 512;
const int32_t device_index = -1; // -1 == default device
const int32_t buffered_frame_count = 10;

pv_recorder_t *recorder = NULL;
pv_recorder_status_t status = pv_recorder_init(
        frame_length,
        device_index,
        buffered_frame_count,
        &recorder);
if (status != PV_RECORDER_STATUS_SUCCESS) {
    // handle PvRecorder init error
}

2. Start recording audio:

pv_recorder_status_t status = pv_recorder_start(recorder);
if (status != PV_RECORDER_STATUS_SUCCESS) {
    // handle PvRecorder start error
}

3. Read frames of audio from the recorder:

// must have length equal to `frame_length` that was given to `pv_recorder_init()`
int16_t *frame = malloc(frame_length * sizeof(int16_t));

while (true) {
    pv_recorder_status_t status = pv_recorder_read(recorder, frame);
    if (status != PV_RECORDER_STATUS_SUCCESS) {
        // handle PvRecorder read error
    }

    // use frame of audio data
    // ...
}

4. Stop recording:

pv_recorder_status_t status = pv_recorder_stop(recorder);
if (status != PV_RECORDER_STATUS_SUCCESS) {
    // handle PvRecorder stop error
}

5. Release resources used by PvRecorder:

pv_recorder_delete(recorder);
free(frame);

Selecting an Audio Device

To print a list of available audio devices:

char **device_list = NULL;
int32_t device_list_length = 0;

pv_recorder_status_t status = pv_recorder_get_available_devices(
        &device_list_length,
        &device_list);
if (status != PV_RECORDER_STATUS_SUCCESS) {
    // handle PvRecorder get audio devices error
}

fprintf(stdout, "Printing devices...\n");
for (int32_t i = 0; i < device_list_length; i++) {
    fprintf(stdout, "index: %d, name: %s\n", i, device_list[i]);
}

pv_recorder_free_available_devices(device_list_length, device_list);

The index of the device in the returned list can be used in pv_recorder_init() to select that device for recording.

Demo

For the PvRecorder C SDK, we offer a demo application that demonstrates how use PvRecorder to record audio to an output audio file in WAV format.

Setup

1. Clone the repository:

git clone --recurse-submodules https://github.com/Picovoice/pvrecorder.git

2. Build the project:

cd demo/c
cmake -S . -B build -DPV_RECORDER_PLATFORM={PV_RECORDER_PLATFORM}
cmake --build build

The {PV_RECORDER_PLATFORM} variable will set the compilation flags for the given platform. Exclude this variable to get a list of possible values.

Usage

To see the usage options for the demo:

./pv_recorder_demo

Get a list of available audio recording devices:

./pv_recorder_demo --show_audio_devices

Record to a file with a given audio device index:

./pv_recorder_demo -o test.wav -d 2

Hit Ctrl+C to stop recording. If no audio device index (-d) is provided, the demo will use the system's default recording device.

For more information about our PvRecorder demo, head over to our GitHub repository.

Resources