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docs: add multichannel routing example
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‎examples/multichannel.maxpat

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}

‎examples/multichannel.rs

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use web_audio_api::context::{
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AudioContext, AudioContextLatencyCategory, AudioContextOptions, BaseAudioContext,
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};
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use web_audio_api::node::{AudioNode, AudioScheduledSourceNode, ChannelInterpretation};
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// Example of multichannel routing, for now the library can only handle up to
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// 32 channels.
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//
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// The example can be tested with a virtual soundcard such as Blackhole
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// https://github.com/ExistentialAudio/BlackHole
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// - select backhole as the default system output
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// - then use blackhole as input in another program to check the example output
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// (see `multichannel.maxpat` if you have Max installed, @todo make a Pd version)
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//
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// `cargo run --release --example multichannel`
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//
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// If you are on Linux and use ALSA as audio backend backend, you might want to run
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// the example with the `WEB_AUDIO_LATENCY=playback ` env variable which will
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// increase the buffer size to 1024
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//
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// `WEB_AUDIO_LATENCY=playback cargo run --release --example multichannel`
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fn main() {
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env_logger::init();
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let latency_hint = match std::env::var("WEB_AUDIO_LATENCY").as_deref() {
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Ok("playback") => AudioContextLatencyCategory::Playback,
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_ => AudioContextLatencyCategory::default(),
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};
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let context = AudioContext::new(AudioContextOptions {
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latency_hint,
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..AudioContextOptions::default()
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});
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// this should be clamped to MAX_CHANNELS (32), even if the soundcard can provide more channels
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println!(
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"> Max channel count: {:?}",
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context.destination().max_channels_count()
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);
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let num_channels = 8;
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context.destination().set_channel_count(num_channels);
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context
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.destination()
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.set_channel_interpretation(ChannelInterpretation::Discrete);
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let merger = context.create_channel_merger(num_channels);
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merger.set_channel_interpretation(ChannelInterpretation::Discrete);
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merger.connect(&context.destination());
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let mut output_channel = 0;
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loop {
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println!("- output sine in channel {:?}", output_channel);
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let now = context.current_time();
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let osc = context.create_oscillator();
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osc.connect_at(&merger, 0, output_channel);
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osc.frequency().set_value(200.);
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osc.start_at(now);
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osc.stop_at(now + 1.);
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output_channel = (output_channel + 1) % num_channels;
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std::thread::sleep(std::time::Duration::from_secs(1));
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}
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}

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