Re: Test report MBP built-in audio device
Re: Test report MBP built-in audio device
- Subject: Re: Test report MBP built-in audio device
- From: "Mikael Hakman" <email@hidden>
- Date: Mon, 25 Aug 2008 14:12:59 +0200
- Organization: Datakonsulten AB
Brian,
None, in fact windowing function free methods were one of the reasons I'm
developing my own set of tools. However, this often but not always requires
special test signals to be generated and feed into the device/software under
the test.
Not that I want to argue against use of windowing function but IMHO the only
good thing multiplying the signal by a windowing function does is to make
result presentation (the charts) more pleasant to look at. It doesn't
increase the precision of the results, rather the opposite. It "smears" out
computed frequency spectrum. In fact windowed DFT of a pure sine wave
results in a DFT of the windowing function itself, not in a single frequency
spike as it should. Spectrogram of an ideal device becomes a ridge of hills
on the diagonal instead of single one pixel wide diagonal line on otherwise
black background. (Sorry for this geodetic metaphor - I don't know how to
express this otherwise).
The other reasons for developing my own toolset are much greater flexibility
of use, my own waterproof validation of the algorithms and their
implementations, and of course the fact that I'm developing entirely new
methods not available before.
PS. Some of the charts in the report, in particular the spectrograms, were
destroyed by Open Office/PDF generation process (TIFF to JPEG conversion I
think). The original charts are much clearer and detailed.
Regards/Mikael
On Sunday, August 24, 2008 8:20 PM, Brian Willoughby wrote:
Mikael,
Which kind of windowing do you apply to the signal before the DFT
analysis? I do not see this information documented anywhere in your
paper.
Brian Willoughby
Sound Consulting
On Aug 24, 2008, at 10:39, Mikael Hakman wrote:
I have ported some of my precision tools for assessing quality of audio
devices and algorithms from Windows to OS X. I have now used the ported
tools to investigate MBP built-in audio device. The test report is at
http://www.dkab.net/Realtek HDA report.pdf.
Regards/Mikael
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