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on SBR QMF analysis filtering

Hello everybody!

I've been trying to implement on Matlab the 64-band SBR QMF analysis filtering as defined in ISO/IEC 14496-3 Amendment 1 on Spectral Band Replication. I have followed the flowchart described in the 64-band analysis and 64-band synthesis filtering.

When I input a single frequency sinewave, the output after synthesis filtering looks fine, a delayed version of the input. Except for glitches which occurs regularly at samples which are multiple of 64. This migh be related to the window shift of the filtering (64 samples). I have also tried to filter and reconstruct an audio signal (song), and the same thing happens. I have struggled for a few days to check my code, and could not find where could I have possibly made a mistake. Below is the image of the reconstructed sinewave.



Please advice on the possible problem. Or is the glitches due to aliasing, hence the filter bank is not PR?

Thanks and regards,
Sam.

 
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