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{sysaudio,examples}: add support for multiple channels

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Signed-off-by: Stephen Gutekanst <stephen@hexops.com>
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Stephen Gutekanst 2022-08-28 23:15:56 -07:00 • committed by Stephen Gutekanst
parent 587ea05d1e
commit 1dc3a4cba8
3 changed files with 82 additions and 52 deletions
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40
examples/sysaudio/main.zig
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@ -6,33 +6,33 @@ const js = mach.sysjs;
pub const App = @This();
audio: sysaudio,
device: sysaudio.Device,
device: *sysaudio.Device,
tone_engine: ToneEngine = .{},
pub fn init(app: *App, _: *mach.Core) !void {
pub fn init(app: *App, core: *mach.Core) !void {
const audio = try sysaudio.init();
errdefer audio.deinit();
const device = try audio.requestDevice(.{ .mode = .output, .channels = 1 });
errdefer device.deinit();
var device = try audio.requestDevice(core.allocator, .{ .mode = .output, .channels = 2 });
errdefer device.deinit(core.allocator);
device.setCallback(callback, app);
device.start();
try device.start();
app.audio = audio;
app.device = device;
}
fn callback(_: *sysaudio.Device, user_data: ?*anyopaque, buffer: []u8) void {
fn callback(device: *sysaudio.Device, user_data: ?*anyopaque, buffer: []u8) void {
// TODO(sysaudio): should make user_data pointer type-safe
const app: *App = @ptrCast(*App, @alignCast(@alignOf(App), user_data));
// Where the magic happens: fill our audio buffer with PCM dat.
app.tone_engine.render(buffer);
app.tone_engine.render(device.descriptor, buffer);
}
pub fn deinit(app: *App, _: *mach.Core) void {
app.device.deinit();
pub fn deinit(app: *App, core: *mach.Core) void {
app.device.deinit(core.allocator);
app.audio.deinit();
}
@ -40,13 +40,12 @@ pub fn update(app: *App, engine: *mach.Core) !void {
while (engine.pollEvent()) |event| {
switch (event) {
.key_press => |ev| {
app.device.start();
try app.device.start();
app.tone_engine.play(ToneEngine.keyToFrequency(ev.key));
},
else => {},
}
}
app.audio.waitEvents();
}
// A simple tone engine.
@ -70,15 +69,16 @@ pub const ToneEngine = struct {
duration: usize,
};
pub fn render(engine: *ToneEngine, buffer: []u8) void {
pub fn render(engine: *ToneEngine, descriptor: sysaudio.DeviceDescriptor, buffer: []u8) void {
// TODO(sysaudio): demonstrate how to properly handle format of the buffer here.
// Right now we blindly assume f32 format, which is wrong (but always right in WASM.)
//
// TODO(sysaudio): get sample rate from callback, don't hard-code it here.
const sample_rate = 44100.0;
const sample_rate = @intToFloat(f32, descriptor.sample_rate.?);
const buf = @ptrCast([*]f32, @alignCast(@alignOf(f32), buffer.ptr))[0 .. buffer.len / @sizeOf(f32)];
const frames = buf.len / descriptor.channels.?;
for (buf) |_, i| {
var frame: usize = 0;
while (frame < frames) : (frame += 1) {
// Render the sample for this frame (e.g. for both left and right audio channels.)
var sample: f32 = 0;
for (engine.playing) |*tone| {
if (tone.sample_counter >= tone.duration) {
@ -104,11 +104,17 @@ pub const ToneEngine = struct {
sample += sine_wave * fade_in * fade_out;
}
buf[i] = sample;
// Emit the sample on all channels.
var channel: usize = 0;
while (channel < descriptor.channels.?) : (channel += 1) {
var channel_buf = buf[channel * frames .. (channel + 1) * frames];
channel_buf[frame] = sample;
}
}
}
pub fn play(engine: *ToneEngine, frequency: f32) void {
// TODO(sysaudio): get from device
const sample_rate = 44100.0;
for (engine.playing) |*tone| {