FIR filtering on the Raspberry Pi

hbdigi-proto-raspberry

A HiFiBerry user asked, if it would be possible to use BruteFIR for room equalization with the DAC. I was pretty sure that BruteFIR only runs on Intel CPUs. Looks like I was wrong. It seems, that BruteFIR also runs on the Raspberry Pi. Alternatively JConvolver also implements FIR filtering on the Raspberry. One commenter noted, that he has a setup running BruteFIR with 32k taps and 50% CPU load on the Raspberry. Wow! This is something we have to look into. Using the HiFiBerry Digi with an additional SPDIF input would allow to use the Raspberry Pi as a flexible room-equalization module.

Has anybody implemented a setup like this already? Let us know!

4 thoughts on “FIR filtering on the Raspberry Pi

    1. Rafael S

      Yes I do it :-)

      There is an unfinished project called FIRtro in a spanish diy audio forum (www.che.es), that is based on Brutefir. The project goals are:

      – Xover based on FIR
      – Bass linearization (GD correction based on lineal phase FIR)
      – ISO-226:2003 Loudness & Volume
      – DRC
      – several sources as MPD, Analog, Shairport, Netjack, etc…

      The FIRtro author, alias RR, has written some Octave routines to design FIRs, but not still has been published :-(

      I hope it will be published soon!

      So I’ve adapted this project into the RPI without the xover. I run 32K tap stero mixed FIR:
      – Lineal phase to linearize bass
      – Minimun phase for DRC

      If MPD/Shairplay + JACK + Brutefir then %CPU is ~90%, but audio is stable. If no JACK is used then ~70%, but sox is needed to avoid Brutefir alsa output “bad state device” breaks… under study

      I am very happy with the result.

      Rafael

      Reply
  1. Pete S

    I am running BRUTEFIR with 65536 taps partitioned in 32×2048 taps with 76% CPU load stable without overclocking using the wolfson audio card an the wolfson-patched Raspberian kernel.

    Reply
    1. Pascal

      Hi Pete, would it be possible to share your Installation with us? I would love to use the same Setup.

      THX

      Reply

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