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<!DOCTYPE html>
<title>Test seamless playback of a series of resampled buffers</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script>
// Permitting some accumulation of rounding to int16_t.
// 64/2^15 would be only just small enough to detect off-by-one-subsample
// scheduling errors with the frequencies here.
const EPSILON = 4.0 / Math.pow(2, 15);
// Offsets test for rounding to nearest rather than up or down.
const OFFSETS = [EPSILON, 1.0 - EPSILON];
// The ratio of resampling is 147:160, so 256 start points is enough to cover
// every fractional offset.
const LENGTH = 256;
function do_test(context_rate, buffer_rate, start_offset) {
var context =
new OfflineAudioContext(2, LENGTH, context_rate);
var merger = context.createChannelMerger(context.destination.channelCount);
merger.connect(context.destination);
// Create an audio signal that will be repeated
var repeating_signal = context.createBuffer(1, 1, buffer_rate);
repeating_signal.getChannelData(0)[0] = 0.5;
// Schedule a series of nodes to repeat the signal.
for (var i = 0; i < LENGTH; ++i) {
var source = context.createBufferSource();
source.buffer = repeating_signal;
source.connect(merger, 0, 0);
source.start((i + start_offset) / buffer_rate);
}
// A single long signal should produce the same result.
var long_signal = context.createBuffer(1, LENGTH, buffer_rate);
var c = long_signal.getChannelData(0);
for (var i = 0; i < c.length; ++i) {
c[i] = 0.5;
}
var source = context.createBufferSource();
source.buffer = long_signal;
source.connect(merger, 0, 1);
source.start(start_offset / buffer_rate);
return context.startRendering().
then((buffer) => {
let series_output = buffer.getChannelData(0);
let expected = buffer.getChannelData(1);
for (var i = 0; i < buffer.length; ++i) {
assert_approx_equals(series_output[i], expected[i], EPSILON,
"series output at " + i);
}
});
}
function start_tests(context_rate, buffer_rate) {
OFFSETS.forEach((start_offset) => {
promise_test(() => do_test(context_rate, buffer_rate, start_offset),
"" + context_rate + " context, "
+ buffer_rate + " buffer, "
+ start_offset + " start");
});
}
start_tests(48000, 44100);
start_tests(44100, 48000);
</script>
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