[linux-audio-dev] BruteFIR + jack = crackling noise?

John Lazzaro lazzaro at CS.Berkeley.EDU
Mon Feb 24 15:00:00 UTC 2003


> we don't care about non-power-of-two periods, i think. however, i do
> consider periods defined in units of times and not frames to be broken
> hardware design. it forces inefficiencies into the software that are
> totally unnecessary.

For what its worth, the SAOL standard has to deal with this problem
too, since the user gets to specify an integer k-rate and an 
integer a-rate. Eric went for this solution:


5.8.5.2.2  krate parameter

<global parameter> -> krate <int>;

The krate global parameter specifies the control rate of the
orchestra.  [...]

The krate parameter shall be an integer value between 1 and the
sampling rate inclusive, specifying the control rate in Hz.  [...]

If the control rate as determined by the previous paragraph is not an
even divisor of the sampling rate, then the control rate is the next
larger integer that does evenly divide the sampling rate.  The control
period of the orchestra is the number of samples, or amount of time
represented by these samples, in one control cycle.


---

This has been controversial, since it limits the ability to use
SAOL to emulate existing coding standards that have non-integer
relationships betweens frames and the sample rate. The win has
been decoder implementation simplicity. 

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John Lazzaro -- Research Specialist -- CS Division -- EECS -- UC Berkeley
lazzaro [at] cs [dot] berkeley [dot] edu     www.cs.berkeley.edu/~lazzaro
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