Clipping in presets?

Question

Several times when I open a Sound and step through the presets I hear audio clipping, a red >0< in the DSP Status window. One of today's Sons du jour, "Chorusing Stereo," does this on the preset "terrifying thunder." Another Son du jour, "KBD: 4 alen weapons Velocity KDB-4" clips unless I turn the VCS gain down from 6.0 to 0.67. Other sounds from the library do this as well.

Does this happen with anyone else? Under Preferences/Performance, I set the system output level pad to -15 dB, the lowest setting, but I still encounter clipping daily, unless I edit a Sound's amplitude from 1 down to .6 or lower, depending on the Sound.

Thanks for any ideas or suggestions!

Answer 1

For the Sounds you reported, we've now added protections against clipping and uploaded the new files to the library.  In both cases, the solution was to prevent internal clipping by scaling the inputs to a mixer by the number of inputs to that mixer.  For those specific Sounds:

• Chorusing Stereo: Since there are three Delays feeding into a Mixer, we scaled each of their amplitudes by 1/3 so their maximum sum would be 1 by setting the Scale field to:

0.7 + ( [randLFO1] L abs * !chorusDepth * 0.3) / 3

We also substituted a new Input to the chorus effect since there was already some clipping in the original recording.

• KBD: 4 alien weapons Velocity KBD-4 is similar in that there is a sample of a gunshot (with some pretty crazy mic bottoming-out DC) feeding into a Delay.  We protected it in exactly the same way, by dividing the Scale parameter (this time by 4, since it is feeding into a MIDI Voice with polyphony 4). 

So the general pattern was: Look for multiple inputs to a mixer and ensure that, if they were to reach their maximum amplitudes, their sum will not exceed 1.  You can be overprotective and divide the amplitude of each input by the total number of inputs.  Or you could multiply their amplitudes by a variable scale factor (in the form of an EventValue) and adjust it to the highest value for which there is no internal clipping.

Kyma signal flow graphs are like analog signal flow paths in that it is possible for clipping to occur at a point within the flow (prior to the output).  If you hear clipping (or see flattened waveshapes in the Oscilloscope display), you can play the Sound at each point along the path to determine where the clipping first occurs and correct it at the earliest point along the path at which it occurs.

Hope this helps.  If you find other Sounds in the library like this please let us know (email is ok) and we will upload new versions for the Sound Library.  Thanks!

 

Comments

Wow, thanks! This is much better than just turning down the level like I was doing.

Answer 2

Yes, it happens to me. The level pad and Output tool appear to attenuate the signal after. SSC has told me that the best way to attenuate it to prevent clipping is to do it in the Sound itself.

It would be very useful if there were a way for the Output Level tool and/or the level pad to handle this since a lot of Sounds don't have Level assigned to a VCS parameter.