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Fundamental frequency model for postfiltering at low bitrates in a transform-domain speech and audio codec

: Das, S.; Bäckström, T.; Fuchs, G.


Meng, H. ; International Speech Communication Association -ISCA-:
Cognitive intelligence for speech processing. 21st Annual Conference of the International Speech Communication Association, INTERSPEECH 2020 : held online due to Covid-19; Shanghai, China, 25-29 October 2020
Red Hook/NY: Curran Associates, 2020
ISBN: 978-1-71382-069-7
DOI: 10.21437/Interspeech.2020
International Speech Communication Association (INTERSPEECH Annual Conference) <21, 2020, Online>
Conference Paper
Fraunhofer IIS ()

Speech codecs can use postfilters to improve the quality of the decoded signal. While postfiltering is effective in reducing coding artifacts, such methods often involve processing in both the encoder and the decoder, rely on additional transmitted side information, or are highly dependent on other codec functions for optimal performance. We propose a low-complexity postfiltering method to improve the harmonic structure of the decoded signal, which models the fundamental frequency of the signal. In contrast to past approaches, the postfilter operates at the decoder as a standalone function and does not need the transmission of additional side information. It can thus be used to enhance the output of any codec. We tested the approach on a modified version of the EVS codec in TCX mode only, which is subject to more pronounced coding artefacts when used at its lowest bitrate. Listening test results show an average improvement of 7 MUSHRA points for decoded signals with the proposed harmonic postfilter.