Full audio fastpath (part2) #141
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* introducing sliding window FFT, which effectively doubles the rate of samples - and FFT results - produced per second. As a side-effect, it also makes FFT a bit less noisy. As sliding window FFT requires double the number of FFT runs, the feature is only enabled on esp32 and esp32-S3.
filter parameter tuning
* limiter on/off : made the logic a bit clearer. * use a simpler way of writing filters: a = n*a + (1-n)*b --> a = a+ n*(b-a) no functional impact.
samples arrive 2x as fast in fast mode - adjust filters accordingly
experiments: user-selectable FFT "windowing" options https://en.wikipedia.org/wiki/Window_function#Cosine-sum_windows
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new: user-selectable "FFT windowing" functions. Why: depending on the audio signal, one or the other window may give better-looking results.
https://en.wikipedia.org/wiki/Window_function#Cosine-sum_windows |
*some filter parameter tinkering * restore FFT_MajPeakSmth in UDP SoundSync receiver
* mic quality: When set to "low noise" or "perfect", only minimal smoothing is performed on the "Mic Volume" input. Every filter adds a delay, so this option can lead to better on-spot responses from effects. * cleanup: removed a few unused variables and unused code.
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This PR allows the audio core to deliver sound data and FFT results 2x faster (43 sps --> 87 sps).
The concept behind this PR is called "sliding window FFT" (aka 50% overlapping FFT). In normal FFT a full batch of samples is first read then analyzed. With sliding window, 50% old samples and 50% new samples are put into each FFT run. This leads to faster responses (new samples arrive twice as fast) and improved accuracy of FFT (samples suppressed by windowing get a second chance in the next run). It also requires twice the number of FFT runs, so you'll need a fast MCU.
Limitations
how to configure
Info Page (with SR_STATS enabled)
Normal mode
== > Fastpath Mode ==>
