This is the accompanying page for the article Audio dequantization using instantaneous frequency authored by Vojtěch Kovanda and Pavel Rajmic.

We present a dequantization method that employs a phase-aware regularizer, originally successfully applied in an audio inpainting problem. The method maintains the temporal continuity of sinusoidal components in the audio signal time-frequency representation and avoids the energy loss artifacts commonly encountered with l₁-based regularization approaches. The proposed method is called the Phase-Aware Audio Dequantizer (PHADQ). The methods are evaluated using the objective metric SDR and PEMO-Q ODG.

Audio examples

You can listen to the EBU SQAM violin audio excerpt. Other examples can be generated by running the available Matlab code. B-PHADQ (consistent/inconsistent) excerpts are generated using 60 algorithm iterations. Recordings corresponding to bit depths of 6 and 7 bps were included in the listening tests.

Original audio
	6 bps	7 bps	8 bps
Quantized audio (quantized)
Reconst. via the CP algorithm, (CP (sparsity-based))
Consistent variant of B-PHADQ (B-PHADQ (consistent))
Inconsistent variant of B-PHADQ (B-PHADQ (inconsistent))

Listening test results

The graphs show the results of a listening MUSHRA test conducted on the EBU SQAM dataset. The test was performed using bit depths of 6 and 7 bps. The subjective listening scores confirm the trends observed in the objective metrics, supporting the validity of our evaluation. The first graph shows an agregate comparison of the methods, while the second graph breaks down the scores according to bit depth (6 and 7 bps).

Evolution of SDR and ODG over time

To justify the chosen number of iterations and to demonstrate the computational time of the methods, we present the following graphs, showing the evolution of SDR and ODG over time for the reconstruction of a single violin signal at bit depths of 6, 7, and 8 bps. The markers in the graphs indicate every fiftieth iteration of the algorithm. One iteration of the CP algorithm takes approximately 0.03 s, while an iteration of both of the B-PHADQ variants takes approximately 0.07 s. The graphs show that the B-PHADQ variants reach the optimal value faster than CP. ODG values were evaluated every fifth iteration.

	SDR	ODG
6 bps
7 bps
8 bps