{'fraction_non_alphanumeric': 0.03229527104959631, 'fraction_numerical': 0.0057670126874279125, 'mean_word_length': 4.748344370860927, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Frequency warping in low delay audio coding

The goal of the presented schemes is to obtain an ultra low delay audio coder with a good performance even at low bit rates (around 64 kb/s). The problem to be solved is to gain sufficient frequency resolution at low frequencies for precise low frequency psycho-acoustics and quantization noise shaping, because the ear has a higher frequency resolution at lower frequencies. Our approach is to use warped linear noise shaping pre- and post-filters, and a short DFT for the psycho-acoustic model (length 256), but with frequency warping. We compare four different psychoacoustic versions: DFT with no warping; DFF without warping using warped pre- and post-filters; warping with the so-called NDFT (WDFT); DFT with all-pass delay chain pre-processing. Listening tests show that the best performance is obtained using WDFT.