The more I look into it, the more it becomes obvious that the Binance RSI is no RSI at all, but some other undisclosed type of measurement. I see it being at odds at every value with both talib and my implementation, but what strikes most is that the Binance (so called) "RSI" is much more stable for some reasons.
For evidence, let's look at this:
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In the marked section from 15:55 to 16:45 the Binance RSI(12) peaks exactly at the high 15:55 candle with just about 60, then declines gradually in a linear fashion.(with the exception of that one tiny uptick at the exact only green candle in this decline) The RSI reaches its lowest point exactly at the price local lowest point.
Now in contrast talib RSI:
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These measurements are intentionally offset by +5min since they are meant to be fed into decision making for the current candle, but you can see a similar high at 16:00 (which is the 15:55 RSI) of 59.65. Some critical difference with it not reaching 60, but so far so good. What is most striking however, is that the talib RSI (and mine) actually take up during the price decline.
This is caused by the moving average "forgetting" reference to the extreme negative candles to the far left, while still holding on to the powerful green uptick in the middle left, so the slow decline after the 15:55 peak is actually not judged as being weighty enough.
That of course is a stark contrast to the, again, linear decline of Binances so called "RSI" that snuggles its ups and downs completely around the general price trend. Thus, the conventional wisdom RSI and what Binance calls RSI cannot be the same thing, since the RSI formula would have to be changed in ways that completely distance it from the original purpose to achieve this effect.
If anything, this reminds me more of the Exponentially Weighted Average from machine learning, where you would essentially just take a percentage of the last, say, RSI, and then add the remaining percentage of the current RSI to get some slight but not overshadowing shift.
Like this (0<=Beta<=1):
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The RSI right would be the known formula, but the displayed "RSI", the Binance-RSI, would be a moving average, which would probably work in this snuggle and flattening effect.
What do you people say? Is this known?