5 Replies Latest reply on Jan 11, 2011 2:24 PM by Matt_Stegner

    Parametric equaliser inconsistent

    AlgolApplications

      This is my first post, and like others, I am much enjoying Adobe Audition for Mac.

       

      However, here is a bug report relating to the Parametric EQ.

       

      In a nutshell, the frequency settings change behind the scenes when you write a file.

       

      I wanted to run an external process on a file that had the bass boosted, and then get rid of the excess bass again.

       

      So in Audition Multitrack at 96kHz I set up a Parametric Equaliser to produce a shelf ("L") boost, +20dB @ 100Hz, and another one set to -20dB @ 100Hz.  I cascaded the two effects on the same track and checked that the result was precisely the same as the original.

       

      Then, with only the boost filter enabled, I used "Export Multitrack Mixdown" to write the boosted file.  I then pulled that file in, and played it with with only the cut filter (-20dB @ 100Hz) enabled.

       

      This also should have produced the same result as the original, but it did not.  After some investigation I concluded that the file as written had bass boost +20dB @ 27.1Hz, i.e. the cut filter needed a setting of -20dB @ 27.1Hz in order to reproduce the original signal.

       

      (BTW I am using the shallower of the two slopes offered by the "L" shelf filter.)

       

      Alternatively, perhaps applying the boost equaliser as a "process" in Waveform view might avoid the problem ?  Well, almost.  That produced a file that needed -20dB @ 99Hz, or something just below 99Hz, to restore the original.  (To complain about the difference between 99Hz and 100Hz may seem pernickety, but for scientific work, these things need to be right.)

      --

       

      Two related curiosities/bugs.

       

      Parametric EQ's display shows the expected boost, but also a spike close to the Nyquist frequency, 48kHz.  In fact the displayed response is mirrored about 24kHz.  I have not checked to see whether or not this is also true of the processed audio !!!

       

      If a session is saved, including a chain of effects some of which are enabled and some not, then when the session is restored, the green/grey indications on the "Toggle power state" buttons are also restored.  However the on/off state of effects themselves is not correctly restored - an effect may be enabled even though its button is grey.

        • 1. Re: Parametric equaliser inconsistent
          Matt_Stegner Adobe Employee

          AlgoApplications,


          I cannot reproduce the issues you are describing here.

           

          "This also should have produced the same result as the original, but it did not.  After some investigation I concluded that the file as written had bass boost +20dB @ 27.1Hz, i.e. the cut filter needed a setting of -20dB @ 27.1Hz in order to reproduce the original signal."

           

          Are you aware of the Panning Law and how that affects the audio rendered from the Multitrack?  Audio rendered from the Multitrack will, by default, be 3 dB lower in level.  Change the Multitrack preferences to "Left/Right Cut" to verify.
          Even with the 3 dB discrepancy, that would not cause a shift in frequency down to 27.1 Hz.
          What we need in order to turn this in to a bug report that can be given to a developer is detailed, step-by-step instructions on how to show the problem.  Can you provide that for me?

           


          "Alternatively, perhaps applying the boost equaliser as a "process" in Waveform view might avoid the problem ?  Well, almost.  That produced a file that needed -20dB @ 99Hz, or something just below 99Hz, to restore the original.  (To complain about the difference between 99Hz and 100Hz may seem pernickety, but for scientific work, these things need to be right.)"

           

          When rendering files in the Editor I also did not see a 1 Hz difference between rendering +20 then -20 @ 100 Hz.  Can you also describe how you are able to get into this situation also?

           


          "Parametric EQ's display shows the expected boost, but also a spike close to the Nyquist frequency, 48kHz.  In fact the displayed response is mirrored about 24kHz.  I have not checked to see whether or not this is also true of the processed audio !!!"

           

          Can you include a screen shot of what you are seeing here?

           


          "If a session is saved, including a chain of effects some of which are enabled and some not, then when the session is restored, the green/grey indications on the "Toggle power state" buttons are also restored.  However the on/off state of effects themselves is not correctly restored - an effect may be enabled even though its button is grey."

           

          There is a known issue (that is now fixed) in the Public Beta build with the Parametric EQ can be internally bypassed by selecting a preset that has been saved from the multitrack.  Are you only seeing this with the Parametric EQ?  Or with many effects?  Can you send a session to me that shows this issue?

           

          -MattS
          • 2. Re: Parametric equaliser inconsistent
            AlgolApplications Level 1

            Dear Matt,

             

            Many thanks for these comments.  It will take me a a while to prepare

            the detailed report you requested, but I am certainly prepared to put

            effort into this.  I have been using Audition 1.5 as my standard

            workhorse for several years and am keen to have something that is just

            as reliable and precise.

             

            Yes I had already encountered the 3dB panning issue and had adjusted

            the preferences.  The problem was a frequency response error, not an

            overall amplitude mismatch.

             

            >> "Parametric EQ's display shows the expected boost, but also a spike

            >> close to the Nyquist frequency, 48kHz.  In fact the displayed

            >> response is mirrored about 24kHz.  I have not checked to see whether

            >> or not this is also true of the processed audio !!!" 

            Can you include a screen shot of what you are seeing here? 

             

            I attach a screenshot showing the spike near 48kHz that results from

            the +20dB 100Hz shelf.  And another where all that is requested is a

            peak at 15kHz.  The display shows a second peak at just under 30kHz.

            In fact the "mirroring" seems to be about 22kHz, not 24kHz as I stated

            previously.  Note that this is with a sampling frequency of 96kHz.

             

            Best regards,

                 PC (AlgolApplications)

            • 3. Re: Parametric equaliser inconsistent
              Matt_Stegner Adobe Employee

              There is no screenshot.  Can you attach it again.

              Please do create the step by step way to reproduce the issue.

              -MattS

              • 4. Re: Parametric equaliser inconsistent
                AlgolApplications Level 1

                Looks as if the two ".png" files I attached must have got stripped off.

                I have put them into a zip this time.  Or perhaps I should send to a

                different e-mail address ?

                 

                Please do create the step by step way to reproduce the issue.

                 

                Good that you asked.  I started Audition, created a new session at

                96kHz, and set up a Parametric Equaliser with the bass boost

                +20dB @ 100Hz ... and the screen display was perfect !

                 

                So in the zip I have put also a .sesx file.  If you click on the first

                effect on track 2 (its "power state" is off) you should see the

                a parametric equaliser window showing a "spike" near 48kHz like the

                one in the screenshot "+20dB 100Hz".  By setting Band 5 to provide

                boost at 15kHz you should also be able to reproduce the other

                screenshot.

                 

                I cannot remember precisely how that .sesx file was created.  It's

                entirely possible that it was in an instance of Audition that had

                previously been running a 44.1kHz session.  That may provide a clue

                but - I have just checked - that alone does not seem to be enough to

                provoke the strange behaviour.

                 

                Thanks again,

                   PC (AlgolApplications)

                • 5. Re: Parametric equaliser inconsistent
                  Matt_Stegner Adobe Employee

                  AlgolApplications,

                  Still no attached files.  Files need to be attached from the web interface, not via the notification email.

                  Feel free to send the screenshotsand session to audbugs@adobe.com with the attention Matt.

                   

                  So, are you saying that you are not seeing a shift in frequency now?

                  Is the Parametriec EQ working correctly now?

                  -MattS