#3434 HIGH Update.: Fully variable Freq slider in Measure

[Zarro Boogs per Child]

#3434: Fully variable Freq slider in Measure
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  Reporter:  arjs              |       Owner:  arjs    
      Type:  defect            |      Status:  new     
  Priority:  high              |   Milestone:  Update.2
 Component:  measure-activity  |     Version:          
Resolution:                    |    Keywords:  slider  
  Verified:  0                 |  
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Comment(by arjs):

 Replying to [comment:7 Hello1024]:
 > It'd be a bit of a structure change for measure, but how about this:
 >
 > If it turns out that at the lower frequency setting there are too many
 data points to plot (ie more than 500 or so), then just start skipping
 data points so there's only 1 per pixel on the x axis.  More accurately,
 you could plot the "range" of pixels that would've been plotted at that x
 axis position and mark the minimum and maximum. (which would give exactly
 the same result as plotting all the points, but would be more efficient)
 That system is arguably better than using a low pass filter because it
 will be more like a "real" oscilloscope, which doesn't have any filters.
 >
 > The above algorithm suggestion can only be implemented after the drawing
 speed problem has been solved.

 The drawing speed problem has been solved (thanks to codyl's efforts we
 have achieved a much higher framerate now)

 Skipping data points as you are suggesting is called 'downsampling' and
 leads to aliases getting folded into the downsampled data. Hence we'd need
 to use low pass filters (And good ones) if we are to downsample the data -
 and implementing those filters is _really_ CPU intensive and in turn slows
 down the framerate.

 >
 > If only it was written in a programming language I knew better! - theres
 so many features I'd like to put in...
 Every activity is written in Python and so is this one. Please feel free
 to contribute !

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Ticket URL: <https://dev.laptop.org/ticket/3434#comment:8>
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