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RE: May I enquire why you persist wasting time?

As to those DAC filters. The A and B recordings are heavily apodized, since they were the result of upsampling four times. As a result, all good linear phase DAC filters are likely to produce similar results on any given file, i.e. the choice of these filters won't matter.

As a demonstration, I took the Piano A file and upsampled two different ways to 352/32fp using iZotope RX4. Both filters used pre-ringing 1.0 (linear phase) and filter-offset 1.0 (half band). The difference was in the filter steepness. One filter had steepness 32 and the other steepness 1020. (The later filter has a much longer impulse response.)

After generating the two upsampled files I created a difference file by mixing the two out of phase. The largest sample in this difference file was at -144 dBfs, which happens to be the level of roundoff error with 32 bit floating point files. Not much happening in the time domain.


On casual listening all three music files sounded the same to me and the difference file sounded completely silent. I tried boosting the difference file by 120dB (!). It was still inaudible and this surprised me. A spectrum plot of the boosted difference file showed that there was a peak of -65 dBfs at 88.4 kHz, which corresponds to a difference at -185dBfs in the unboosted difference file. There were also time variance in the background level that appeared to be correlated to the loudness of the original piano playing, but the boosted difference file had this time varying noise at even lower levels. (I would guess this has to do with the use of 32 bit floating point to represent the resampled files.)

Tony Lauck

"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar


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  • RE: May I enquire why you persist wasting time? - Tony Lauck 04/28/1510:01:49 04/28/15 (0)

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