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Apply REW filters to Left and right + Both

TigerbotHesh

January 02, 2022 17:22

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I am running HifiBerryOS on a Pi 3B+ with the DAC+ DSP board and attempting to apply individual EQ filters generated by REW to the left and right channels separately. Each channel has a set of filters below 400Hz. Additionally, I would like to experiment with applying an EQ curve to both channels in the higher frequencies.

Reading through older forum posts I can see that when I use the "dsptoolkit apply-rew-filters-left filters.txt" (or right) command, I should ignore the message that says "filters configured on both channels" as the message is wrong and the filters were actually applied correctly on separate channels. 

My questions:

1. Is it still accurate that applying separate channel filters in the way described above works as intended, and the resulting success message is incorrect?
2. If I were to next apply a filter to both channels with "dsptoolkit apply-rew-filters filters.txt" would this then overwrite the individual channel filters previously applied? If so, does this mean you are able to apply an EQ to the left and right separately, or both at once, but not a combination of separate and summed?
3. Is there a way for dsptoolkit to return the currently applied filters?  Something similar to what's returned when you apply them perhaps (a list of frequencies and their gain/attenuations)? I don't see them in the web app but my understanding is EQ here is different and wouldn't show up there anyways.

 

I realize applying EQ to separate channels can create phasing issues. As I experiment with my setup I simply want to confirm how things work and what limitations may exist with dsptoolkit so I can be confident in my process and results.

Thank you in advance fo the help! 

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3 comments

• 0
  
  HiFiBerry team January 02, 2022 20:33

  While you can apply filters from command line, these will be overwritten by the GUI when it restarts. Therefore, with HiFiBerryOS, you should enter these filters via the UI. You can use different filters for left and right in the UI.

• 0
  
  TigerbotHesh January 02, 2022 20:38

  Thanks for the response. I may switch OS in the future to try other options. If that's the case, how would dsptoolkit work as it relates to my questions above? I know I would need to store the filters to the profile to survive a restart, using the store command.

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  HiFiBerry team January 03, 2022 08:14

  1. Is it still accurate that applying separate channel filters in the way described above works as intended, and the resulting success message is incorrect?
  
  Should be. Just test it.
  
  2. If I were to next apply a filter to both channels with "dsptoolkit apply-rew-filters filters.txt" would this then overwrite the individual channel filters previously applied? If so, does this mean you are able to apply an EQ to the left and right separately, or both at once, but not a combination of separate and summed?
  
  Yes, this would overwrite previously applied filters.
  
  3. Is there a way for dsptoolkit to return the currently applied filters?  Something similar to what's returned when you apply them perhaps (a list of frequencies and their gain/attenuations)? I don't see them in the web app but my understanding is EQ here is different and wouldn't show up there anyways.
  
  No, you can read the memory from the DSP but this won't be translated into filter coefficients