pipewire-recorder-zig/src/main.zig

const data_struct = struct {
    loop: ?*pipewire.pw_main_loop,
    stream: ?*pipewire.pw_stream,
    format: pipewire.spa_audio_info,
    move: u1,
};

/// our data processing function is in general:
///
///  struct pw_buffer *b;
///  b = pw_stream_dequeue_buffer(stream);
///
///  .. consume stuff in the buffer ...
///
///  pw_stream_queue_buffer(stream, b);
export fn on_process(userdata: ?*anyopaque) void {
    const data: *data_struct = @ptrCast(@alignCast(userdata));
    const b_optional: ?*pipewire.pw_buffer = pipewire.pw_stream_dequeue_buffer(data.stream);
    var buf: *pipewire.spa_buffer = undefined;

    var samples_optional: ?[*]f32 = undefined;
    var max: f32 = undefined;

    var c: u32 = 0;
    var n: u32 = undefined;
    var n_channels: u32 = undefined;
    var n_samples: u32 = undefined;
    var peak: u32 = undefined;

    if (b_optional) |b| {
        buf = b.buffer;
        samples_optional = @ptrCast(@alignCast(buf.datas[0].data));
        if (samples_optional) |samples| {
            n_channels = data.format.info.raw.channels;
            n_samples = buf.datas[0].chunk.*.size / @sizeOf(f32);

            if (data.move != @as(u1, 0))
                _ = pipewire.fprintf(pipewire.stdout, "%c[%dA", @as(u8, 0x1b), n_channels + 1);

            _ = pipewire.fprintf(pipewire.stdout, "captured %d samples\n", n_samples / n_channels);
            while (c < data.format.info.raw.channels) : (c += 0) {
                max = 0.0;
                n = c;
                while (n < n_samples) : (n += n_channels)
                    max = @max(max, @abs(samples[n]));

                peak = @bitCast(@min(@max(max * 30.0, 0.0), 39.0));

                _ = pipewire.fprintf(
                    pipewire.stdout,
                    "channel %d: |%*s%*s| peak:%f\n",
                    c,
                    peak + 1,
                    "*",
                    40 - peak,
                    "",
                    max,
                );
            }
            data.move = @intFromBool(true);
            _ = pipewire.fflush(pipewire.stdout);

            _ = pipewire.pw_stream_queue_buffer(data.stream, b);
        }
    } else {
        pw_log_warn("out of buffers: %m");
    }
}

/// Be notified when the stream param changes. We're only looking at the format changes.
export fn on_stream_param_changed(_data: ?*anyopaque, id: u32, param_optional: ?*const pipewire.spa_pod) void {
    const data: *data_struct = @ptrCast(@alignCast(_data));

    // NULL means to clear the format
    if (param_optional) |param| {
        if (id != pipewire.SPA_PARAM_Format) {
            if (pipewire.spa_format_parse(param, &data.format.media_type, &data.format.media_subtype) >= 0) {
                if (data.format.media_type == pipewire.SPA_MEDIA_TYPE_audio and data.format.media_subtype == pipewire.SPA_MEDIA_SUBTYPE_raw) {
                    _ = pipewire.spa_format_audio_raw_parse(param, &data.format.info.raw);
                    _ = pipewire.fprintf(pipewire.stdout, "capturing rate:%d channels:%d\n", data.format.info.raw.rate, data.format.info.raw.channels);
                }
            }
        }
    }
}

const stream_events = pipewire.pw_stream_events{
    .version = pipewire.PW_VERSION_STREAM_EVENTS,
    .param_changed = on_stream_param_changed,
    .process = on_process,
};

export fn do_quit(userdata: ?*anyopaque, signalnumber: c_int) void {
    const data: *data_struct = @ptrCast(@alignCast(userdata));
    _ = pipewire.pw_main_loop_quit(data.loop);
    _ = signalnumber;
}

pub fn main() !void {
    var data: data_struct = undefined;
    var params: [1][*c]const pipewire.spa_pod = undefined;
    var buffer: [1024]u8 = undefined;
    var props: *pipewire.pw_properties = undefined;
    var b: pipewire.spa_pod_builder = pipewire.spa_pod_builder{
        .data = &buffer,
        .size = @sizeOf([1024]u8),
        ._padding = 0,
        .state = .{
            .flags = 0,
            .offset = 0,
            .frame = null,
        },
        .callbacks = .{
            .data = null,
            .funcs = null,
        },
    };

    const argv = std.os.argv;
    var c_ptr: [*c][*c]u8 = @ptrCast(argv.ptr);
    var argc: c_int = @intCast(std.os.argv.len);

    pipewire.pw_init(&argc, &c_ptr);

    std.log.info(
        \\ Compiled with libpipewire {s}
        \\ Linked with libpipewire {s},
    , .{
        pipewire.pw_get_headers_version(),
        pipewire.pw_get_library_version(),
    });

    data.loop = pipewire.pw_main_loop_new(null);

    _ = pipewire.pw_loop_add_signal(pipewire.pw_main_loop_get_loop(data.loop), pipewire.SIGINT, do_quit, &data);
    _ = pipewire.pw_loop_add_signal(pipewire.pw_main_loop_get_loop(data.loop), pipewire.SIGTERM, do_quit, &data);

    props = pipewire.pw_properties_new(
        pipewire.PW_KEY_MEDIA_TYPE,
        "Audio",
        pipewire.PW_KEY_MEDIA_CATEGORY,
        "Capture",
        pipewire.PW_KEY_MEDIA_ROLE,
        "Music",
        @as(?*anyopaque, @ptrFromInt(0)),
    );

    if (argc > 1) _ = pipewire.pw_properties_set(props, pipewire.PW_KEY_TARGET_OBJECT, argv[1]);

    data.stream = pipewire.pw_stream_new_simple(
        pipewire.pw_main_loop_get_loop(data.loop),
        "audio-capture",
        props,
        &stream_events,
        &data,
    );

    params[0] = pipewire.spa_format_audio_raw_build(
        &b,
        pipewire.SPA_PARAM_EnumFormat,
        &pipewire.spa_audio_info_raw{ .format = pipewire.SPA_AUDIO_FORMAT_F32 },
    );

    _ = pipewire.pw_stream_connect(data.stream, pipewire.PW_DIRECTION_INPUT, pipewire.PW_ID_ANY, pipewire.PW_STREAM_FLAG_AUTOCONNECT | pipewire.PW_STREAM_FLAG_MAP_BUFFERS | pipewire.PW_STREAM_FLAG_RT_PROCESS, params[0..].ptr, @as(u32, 1));

    _ = pipewire.pw_main_loop_run(data.loop);

    pipewire.pw_stream_destroy(data.stream);
    pipewire.pw_main_loop_destroy(data.loop);
    pipewire.pw_deinit();
}

extern "c" fn pw_log_warn(...) void;

const std = @import("std");

const pipewire = @cImport({
    @cInclude("pipewire/pipewire.h");
    @cInclude("spa/param/audio/format-utils.h");
});