libm17 has just been updated with polyphase square root raised cosine filter taps, for both 24 and 48kHz sample rates. Polyphase filters offer great speed improvement over classic FIR filter implementations. This approach is also being implemented in OpenRTX.
Tested on an STM32F405 (modified Nokia 3310) – filtered 1,000 frames with 10x upsampling (-Os optimization):
New code is more than 10 times faster!
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