apple2js/js/ui/tape.ts

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import { TapeData } from '../types';
import Apple2IO from '../apple2io';
import { debug } from '../util';
export const TAPE_TYPES = ['wav', 'aiff', 'aif', 'mp3', 'm4a'] as const;
export default class Tape {
constructor(private readonly io: Apple2IO) {}
public doLoadLocalTape(file: File, done?: () => void) {
const kHz = this.io.getKHz();
// Audio Buffer Source
let context: AudioContext;
if (AudioContext) {
context = new AudioContext();
} else {
window.alert('Not supported by your browser');
done && done();
return;
}
const fileReader = new FileReader();
fileReader.onload = (ev: ProgressEvent) => {
const target: FileReader = ev.target as FileReader;
const result: ArrayBuffer = target.result as ArrayBuffer;
context.decodeAudioData(result).then((buffer) => {
const buf: TapeData = [];
const data = buffer.getChannelData(0);
let datum = data[0];
let old = (datum > 0.0), current;
let last = 0;
let delta: number;
debug(`Sample Count: ${data.length}`);
debug(`Sample rate: ${buffer.sampleRate}`);
for (let idx = 1; idx < data.length; idx++) {
datum = data[idx];
if ((datum > 0.1) || (datum < -0.1)) {
current = (datum > 0.0);
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if (current !== old) {
delta = idx - last;
if (delta > 2000000) {
delta = 2000000;
}
let ival = delta / buffer.sampleRate * 1000;
if (ival >= 0.550 && ival < 0.750) {
ival = 0.650; // Header
} else if (ival >= 0.175 && ival < 0.225) {
ival = 0.200; // sync 1
} else if (ival >= 0.225 && ival < 0.275) {
ival = 0.250; // 0 / sync 2
} else if (ival >= 0.450 && ival < 0.550) {
ival = 0.500; // 1
} else {
// debug(idx + ' ' + buf.length + ' ' + ival);
}
buf.push([ival * kHz, current]);
old = current;
last = idx;
}
}
}
this.io.setTape(buf);
if (done) {
done();
}
}, (error: Error) => {
window.alert(error.message);
});
};
fileReader.readAsArrayBuffer(file);
}
}