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audio: cleanup pitch_scale 

- use better normalization: (value - 32768) / 32768.0;
- use DataView to access little-endian 16bit raw audio data

Signed-off-by: Dietmar Maurer <dietmar@proxmox.com>
This commit is contained in:
Dietmar Maurer 2025-05-07 12:44:10 +02:00
parent 3721da90dc
commit 58c6ad6113
1 changed files with 7 additions and 4 deletions
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11
core/audio.js
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@ -23,7 +23,8 @@
// //
// ## Audio format // ## Audio format
// //
// We use/expect U16 raw audio data. // We use/expect U16, little endian, raw audio data,
// interleaved channel data: [L0, R0, L1, R1, ...]
import * as Log from './util/logging.js'; import * as Log from './util/logging.js';
@ -38,6 +39,7 @@ export default class Audio {
// ===== PROPERTIES ===== // ===== PROPERTIES =====
this._sample_rate = sample_rate; this._sample_rate = sample_rate;
this._nchannels = nchannels; this._nchannels = nchannels;
this._little_endian = true;
} }
// ===== PROPERTIES ===== // ===== PROPERTIES =====
@ -127,6 +129,7 @@ export default class Audio {
_pitchScale(payload, factor) { _pitchScale(payload, factor) {
let sample_bytes = 2*this._nchannels; let sample_bytes = 2*this._nchannels;
let new_length = Math.ceil(payload.length/(factor*sample_bytes)); let new_length = Math.ceil(payload.length/(factor*sample_bytes));
const payload_view = new DataView(payload);
let buffer = this._context.createBuffer(this._nchannels, new_length, this._sample_rate); let buffer = this._context.createBuffer(this._nchannels, new_length, this._sample_rate);
for (let ch = 0; ch < this._nchannels; ch++) { for (let ch = 0; ch < this._nchannels; ch++) {
@ -138,14 +141,14 @@ export default class Audio {
let second_weight = pos_float % 1; let second_weight = pos_float % 1;
let first_weight = 1 - second_weight; let first_weight = 1 - second_weight;
let p = j*sample_bytes + channel_offset; let p = j*sample_bytes + channel_offset;
let value0 = payload[p] + payload[p+1]*256; let value0 = payload_view.getUint16(p, this._little_endian);
p += sample_bytes; p += sample_bytes;
let value1 = value0; let value1 = value0;
if (p < payload.length) { if (p < payload.length) {
value1 = payload[p] + payload[p+1]*256; value1 = payload_view.getUint16(p, this._little_endian);
} }
let value = (value0*first_weight + value1*second_weight); let value = (value0*first_weight + value1*second_weight);
channel[i] = (value / 32768.0) - 1.0; channel[i] = (value - 32768) / 32768.0;
} }
} }
return buffer; return buffer;