title: Questions about IPP (Intel performance primitives) IIR filters
body: <p>I'm currently investigating IPP 8 and have a few problems with the biquad IIR support:</p>
  
  <ul>
  <li><p>ippsIIRInitAlloc is now deprecated, fine by me, we can allocate manually. However I need to be able to changes the IIR taps WITHOUT changing the filter state. ippsIIRInit seems to destroy the delay line, which makes it unusable. So the only way to change taps without using deprecated functions is to copy the delay line and set it back with ippsIIRInit, which is unacceptable. So what am I missing?</p></li>
  <li><p>In many cases I use multiple instances of the same filter - same taps, but used on multiple signals. Right now it seems I need to allocate the IppsIIRState for each of the signals, which means duplicate the taps. It's always just a single biquad, so no big deal, but...</p></li>
  <li><p>The requested "new" method using ippMalloc and ippsIIRInit made me check the sizes of the IppsIIRState structures and these are HUGE - like over 4k for a single biquad filter! For 1000 filters that makes 4MB, that looks hardly efficient, especially since I need just a single biquad, so state structure of "2 numbers" (plus taps, plus anything for optimizations, but that could hardly be 4k). Am I missing something or is it a bug?</p></li>
  </ul>