1 Topic by bobkatz (edited by bobkatz 2009-06-18 19:56:15)

  • From: Orlando, Florida, USA
  • Registered: 2007-12-16
  • Posts: 68

Topic: Bug in RMS meter when oversampling....

Today I was playing back a standard 96 kHz -14 dBFS stereo test tone that I use to line up my analog equipment and I discovered (for the first time, I have no idea why I didn't notice it before) that ONLY when OVERSAMPLING is turned on, the RIGHT channel of this wave reads 0.3 dB too high on the RMS section of the 2 channel RME digicheck meter. So this may be a bug in oversampling, only on the right channel, OR, some anomaly in the source file which causes the RME meter to read it higher. I think you should look into this, especially because it's only on one channel, and only on the 2 channel meter. It affects the K-System or no K-System equally. But it does not show on the multichannel meter although I forgot to try oversampling on it to test that there.

Actually, this is the right channel of this particular sine wave. If I reverse the panning in Sequoia, the LEFT channel meter of the digicheck reads too high. I wonder if there is a distortion difference in the right channel of this sine wave that the Digicheck meter is actually measuring? That would be interesting, since I generated this stereo sine wave using Sequoia's generator. Yours is the only oversampling RMS meter that I own so I cannot compare the results against any other "authority".

To see the effect, you can download the sine wave from ftp.digido.com   Your name is rmedebug   Your password is rmedebug.  The file name is  #1 khz -14 dBFS 96k.wav.

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2 Reply by MC

  • MC
  • MC
  • Administrator
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  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 25,596

Re: Bug in RMS meter when oversampling....

Bob, on my system both channels show the same reading in 2 Bar level meter, RMS and Oversampling active.

When you say <If I reverse the panning in Sequoia, the LEFT channel meter of the digicheck reads too high> it's clear that this is not a DC problem. As the file reads correctly here I bet that some setting in Sequoia causes this.

Regards
Matthias Carstens
RME

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  • From: Orlando, Florida, USA
  • Registered: 2007-12-16
  • Posts: 68

Re: Bug in RMS meter when oversampling....

MC wrote:

Bob, on my system both channels show the same reading in 2 Bar level meter, RMS and Oversampling active.

When you say <If I reverse the panning in Sequoia, the LEFT channel meter of the digicheck reads too high> it's clear that this is not a DC problem. As the file reads correctly here I bet that some setting in Sequoia causes this.

Thanks. Very interesting, MC. I'm running a Sequoia beta, I'll have to check this in the previous release because they've done a lot of changing under the hood. When I made a 900 Hz file with identical parameters it played fine on the RME meters and there was no difference between OVS or no OVS...  I'm also running 24 bit dither but I can't believe it's making an 0.3 dB difference or acting that strangely.

You did try to see if you saw differences with and without oversampling?  Something's up with the right channel of this "sine wave". Perhaps it has some negligible distortion that would raise the RMS level?

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