project

PvSpeaker Source Project

Requirements

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

Compatibility

• Linux (x86_64)
• macOS (x86_64, arm64)
• Windows (amd64)
• Raspberry Pi (3, 4 and 5)

Compiling

Run the following commands to build and test ({OUTPUT_DIR} can be empty if you wish not to copy):

git submodule update --init --recursive
cmake -S . -B build -DOUTPUT_DIR={OUTPUT_DIR} -DPV_SPEAKER_PLATFORM={PV_SPEAKER_PLATFORM}
cmake --build build

The variable {OUTPUT_DIR} will be used to select the directory to copy the shared object after a successful compilation. {OUTPUT_DIR} should be a directory relative to the lib directory.

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

Usage

1. Create a PvSpeaker object:

#include "pv_speaker.h"

const int32_t sample_rate = 22050;
const int16_t bits_per_sample = 16;
const int32_t buffer_size_secs = 20;
const int32_t device_index = -1; // -1 == default device

pv_speaker_t *speaker = NULL;
pv_speaker_status_t status = pv_speaker_init(
        sample_rate,
        bits_per_sample,
        buffer_size_secs,
        device_index,
        &speaker);
if (status != PV_SPEAKER_STATUS_SUCCESS) {
    // handle PvSpeaker init error
}

2. Start the speaker:

pv_speaker_status_t status = pv_speaker_start(speaker);
if (status != PV_SPEAKER_STATUS_SUCCESS) {
    // handle PvSpeaker start error
}

3. Write PCM data to the speaker:

int32_t num_samples;
int8_t *pcm = get_pcm_data(&num_samples);
int32_t written_length = 0;

pv_speaker_status_t status = pv_speaker_write(speaker, pcm, num_samples, &written_length);
if (status != PV_SPEAKER_STATUS_SUCCESS) {
    // handle PvSpeaker write error
}

4. Wait for buffered audio to finish playing:

int32_t num_samples;
int8_t *pcm = get_pcm_data(&num_samples);
int32_t written_length = 0;

pv_speaker_status_t status = pv_speaker_flush(speaker, pcm, num_samples, &written_length);
if (status != PV_SPEAKER_STATUS_SUCCESS) {
    // handle PvSpeaker flush error
}

5. Stop the speaker:

pv_speaker_status_t status = pv_speaker_stop(speaker);
if (status != PV_SPEAKER_STATUS_SUCCESS) {
    // handle PvSpeaker stop error
}

6. Release resources used by PvSpeaker:

pv_speaker_delete(speaker);

Selecting an Audio Device

To print a list of available audio devices:

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

pv_speaker_status_t status = pv_speaker_get_available_devices(&device_list_length, &device_list);
if (status != PV_SPEAKER_STATUS_SUCCESS) {
    // handle PvSpeaker 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_speaker_free_available_devices(device_list_length, device_list);

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

Refer to pv_speaker_demo.c for a full example of how to use pv_speaker to capture audio in C.