EXDF mode and how ak449X DAC's interpolator handle a hi res input?

EXDF (external digital filter) mode for AKM DACs sounds interesting but with practically zero discussion on this. It does not use typical I2S and expects split LDATA and RDATA with BCLK and WCLK (i.e LRCLK?) . I expected AKM SRC chip could output in this format but doesnt look to be case, not sure how or where you would get this format.

The idea of pre-upsampling on PC is appealing and they are some excellent options that should offer some of best performing filters.
In practice I have not found PC upsampling to be of any real benefit with AKM4493 ES9038X DACs, different yes but not a subjective improvement.
With EXDF it could be a different story.
The 9038 DACs had the spotlight for a while but now with the AK4499 which also supports this mode it may be of interest to a lot of people



Also it seems 8X filtering is applied at 44.1kHz in the AK449X DACs, would that mean upsampling to 352.8 skips on-chip filtering? and is adjusted to 4x at 88.2 and 2x at 176.4 respectively?
 
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