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DEMO_AUDIOCOMPRESSION - Audio compression using N-term approx
Description
This demos shows how to do audio compression using best N-term approximation of an wmdct transform.
The signal is transformed using an orthonormal wmdct transform. Then approximations with a fixed number N of coefficients are obtained by:
- Linear approximation: The N coefficients with lowest frequency index are kept.
- Non-linear approximation: The N largest coefficients (in magnitude) are kept.
The corresponding approximated signal can be computed using iwmdct.
Rate-distorition plot
The figure shows the output Signal to Noise Ratio (SNR) as a function
of the number of retained coefficients.
Note: The inverse WMDCT is not needed for computing computing SNRs. Instead Parseval theorem states that the norm of a signal equals the norm of the sequence of its wmdct coefficients.