Precalculate common PWMAudio dividers, avoid noise #2714
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Calculating the DMA clock divider for PWMAudio can take a very long time because there are 65K floating point divisions required. But most audio will be one of a dozen sample rates, so it is possible to precalculate the rates on the host and use a small lookup table to avoid any math at all. Removes occasional scratching in PWMAudio when the BackgroundAudio library changes sample rates.
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Calculating the DMA clock divider for PWMAudio can take a very long time because there are 65K floating point divisions required. But most audio will be one of a dozen sample rates, so it is possible to precalculate the rates on the host and use a small lookup table to avoid any math at all. Removes occasional scratching in PWMAudio when the BackgroundAudio library changes sample rates.
Related to earlephilhower/BackgroundAudio#3