Thread: [Sv1-devel] [ sv1-Bugs-3038909 ] Spectrum view reports wrong Hz frequencies, if large frame
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From: SourceForge.net <no...@so...> - 2010-08-03 16:51:30
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Bugs item #3038909, was opened at 2010-08-03 16:51 Message generated for change (Tracker Item Submitted) made by danstowell You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=825705&aid=3038909&group_id=162924 Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: None Group: None Status: Open Resolution: None Priority: 5 Private: No Submitted By: Dan Stowell (danstowell) Assigned to: Nobody/Anonymous (nobody) Summary: Spectrum view reports wrong Hz frequencies, if large frame Initial Comment: * Load an audio file (preferably one with some structured frequency content, e.g. with a strong tone at a known freq). In my case it was birdsong recordings, WAV, 44.1 kHz. * Get a spectrum (not a spectrogram). Identify a notable feature of the spectrum at a short-ish resolution (in my case it was a dropoff due to a shelving filter at around 18 kHz, easily visible in an FFT of size 8192). I do this by moving my mouse over the feature, and looking at the visual readout of bin number and frequency. * Change window size to 262144. * Mouseover the feature again. The frequency is not reported correctly. For me the bin number was 111485--111616, which seemed about right, but the frequency was reported as 2370--2392 Hz (it should have been something around 18 kHz). I can manually calculate what the real frequencies should have been reported as (assuming the bin indices are OK): 18754--18777 Hz. So about a factor of 8 wrong. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=825705&aid=3038909&group_id=162924 |
From: SourceForge.net <no...@so...> - 2010-08-03 16:54:38
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Bugs item #3038909, was opened at 2010-08-03 16:51 Message generated for change (Comment added) made by danstowell You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=825705&aid=3038909&group_id=162924 Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: None Group: None Status: Open Resolution: None Priority: 5 Private: No Submitted By: Dan Stowell (danstowell) Assigned to: Nobody/Anonymous (nobody) Summary: Spectrum view reports wrong Hz frequencies, if large frame Initial Comment: * Load an audio file (preferably one with some structured frequency content, e.g. with a strong tone at a known freq). In my case it was birdsong recordings, WAV, 44.1 kHz. * Get a spectrum (not a spectrogram). Identify a notable feature of the spectrum at a short-ish resolution (in my case it was a dropoff due to a shelving filter at around 18 kHz, easily visible in an FFT of size 8192). I do this by moving my mouse over the feature, and looking at the visual readout of bin number and frequency. * Change window size to 262144. * Mouseover the feature again. The frequency is not reported correctly. For me the bin number was 111485--111616, which seemed about right, but the frequency was reported as 2370--2392 Hz (it should have been something around 18 kHz). I can manually calculate what the real frequencies should have been reported as (assuming the bin indices are OK): 18754--18777 Hz. So about a factor of 8 wrong. ---------------------------------------------------------------------- >Comment By: Dan Stowell (danstowell) Date: 2010-08-03 16:54 Message: Aha - it looks like the frequencies are correct as far as roughly 16384 (i.e. 2**14), after which point they wrap around. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=825705&aid=3038909&group_id=162924 |