def test_wavetable_synth_is_accurate(self,
batch_size,
frequency,
amplitude,
n_wavetable,
wavetable_frames):
"""Tests accuracy of wavetable synthesizer.
Generate a sine wave wavetable synthesizer and compare to the analytic
form. Error will vary with the size of the lookup table, but should stay
below a threshold for moderate sized tables.
Args:
batch_size: Number of batch examples in the test phase signal.
frequency: Frequency of the carrier signal in Hertz.
amplitude: Amplitude of the carrier signal.
n_wavetable: Number of samples in the wavetable.
wavetable_frames: Number of wavetables over time.
"""
sample_rate = 16000
seconds = 0.1
n_samples = int(sample_rate * seconds)
n_cycles = seconds * frequency
n_frames = 100
two_pi = 2.0 * np.pi
wavetable = np.sin(np.linspace(0, two_pi, n_wavetable).astype(np.float32))
wavetable = np.tile(wavetable[np.newaxis, :], [batch_size, 1])
if wavetable_frames > 0:
wavetable = np.tile(wavetable[:, np.newaxis, :], [1, wavetable_frames, 1])
wav_np = amplitude * np.sin(two_pi * np.linspace(0, n_cycles, n_samples))
wav_np = np.tile(wav_np[np.newaxis, :], [batch_size, 1]).astype(np.float32)
amplitudes = np.ones([batch_size, n_frames, 1]) * amplitude
frequencies = np.ones([batch_size, n_frames, 1]) * frequency
with self.cached_session() as sess:
wav_tf = sess.run(core.wavetable_synthesis(
frequencies,
amplitudes,
wavetable,
n_samples,
sample_rate
))
pad = n_samples // n_frames # Ignore edge effects.
difference = np.abs(wav_np[:, pad:-pad] - wav_tf[:, pad:-pad]).mean()
threshold = 3e-2
self.assertLessEqual(difference, threshold)
def get_signal(self, amplitudes, wavetables, f0_hz):
"""Synthesize audio with additive synthesizer from controls.
Args:
amplitudes: Amplitude tensor of shape [batch, n_frames, 1]. Expects
float32 that is strictly positive.
wavetables: Tensor of shape [batch, n_frames, n_wavetable].
f0_hz: The fundamental frequency in Hertz. Tensor of shape [batch,
n_frames, 1].
Returns:
signal: A tensor of of shape [batch, n_samples].
"""
wavetables = core.resample(wavetables, self.n_samples)
signal = core.wavetable_synthesis(amplitudes=amplitudes,
wavetables=wavetables,
frequencies=f0_hz,
n_samples=self.n_samples,
sample_rate=self.sample_rate)
return signal
