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Rockbox mail archiveSubject: Log base 2Log base 2
From: Jeff Waltzer <jeffwaltzer_at_yahoo.com>
Date: Thu, 19 Sep 2002 11:17:58 -0700 (PDT) One could do a primitive approximation of a Log base 2 function by rotating the bits to find the left most location set bit. This would be good if all you need is a number from 0 to 15. --- Jack Peel <jhp_at_cypress.com> wrote: > Philipp Pertermann wrote: > > > From: "Jack Peel" <jhp_at_cypress.com> > > > > > Also could you put "clip" "lights" on it so that if > > the MP3 goes > > > > > to full scale it shows a different symbol and it hangs > > out longer > > > > > so that we know if the MP3 itself is clipping ? > > > > > > > > Yes, I could. > > > > Now I fiddled a bit with that. I don't like it much because > > it is incredibly unreliable. The 'quasi peak detector' of > > the mas is very 'quasi' but not so much a 'peak detector'. > > If we don't read the peak value exactly when it happens we > > miss it. I now installed a polling thread that reads out the > > mas quite often but still many peaks remain undetected. So > > the whole peak meter is a toy and not a reliable measuring > > tool. > > > > Phil > > Well, in theory the human ear cannot hear a clip if it is only a few > samples long, so we would only be interested in seeing a "clip" if > it were several samples long. But after thinking about it, seeing the > peak level indicators at full scale will tell you enough. And the user > can set how long they stick around already. It would be nice however > to do the "set until reset" function on the peak meters :) The only > problem is how do we easily reset them without having to go through > 3 levels of menus :) I guess you could just add it to one of the F2 or > F3 > key functions from the wps screen. > > Any luck with the linear to log conversion ? > > I was thinking about the lookup table issue, and you could probably drop > > a couple of bits off of the number to reduce the size of the table and > we > would probably never be able to tell. Since it is a 15 bit number you > could > probably drop 5 bits and I would never be able to tell, maybe even 7 > bits. > Another Idea is that we only really care about the accuracy when we are > close to the top so you might be able to "shape" the table to have > more accuracy at the top. The Idea is that -1 dB and -2 dB are VERY > difference, however -41 dB and -42 dB are not. It may however be > too much coding trouble to handle the shaped table. > > Just some Ideas :) > > Jack > > ===== Whoever fights monsters should see to it that in the process he doesn't become a monster. --Frederick Wilhelm Nietsche __________________________________________________ Do you Yahoo!? New DSL Internet Access from SBC & Yahoo! http://sbc.yahoo.com Received on 2002-09-19 Page template was last modified "Tue Sep 7 00:00:02 2021" The Rockbox Crew -- Privacy Policy |