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From: Robert Scott on 13 Jun 2008 10:24
We have received a report of a peculiar problem with the HTC Touch PDA/phone
from one of our customers. He has tried our audio spectrum analysis software on
three different units, and on each unit, our Fourier spectrum display, when
listening to a pure sine-wave tone, shows not just a single peak from the FFT
analysis, but it shows the central peak surrounded by sidebands spaced every 11
Hz or so. To me this sounds like phase modulation, such as you would get if the
audio samples had a periodic phase discontinuity.

We sample continuously at 22050 samples per second using multiple buffers of
1024 samples per buffer. This comes out to 21.53 buffers per second - close to
double the reported spacing in the sidebands. I hypothesize that our buffers
are not getting filled by the system audio drivers with 1024 samples of
continuous data. If the drivers happened to drop a few samples from one buffer
to the next, that would result in exactly the kind of phase modulation that our
Fourier analysis is indicating.

Does anyone know if there are any reported audio problems that would affect a
listening program that samples at 22050 samples per second and uses 16 buffers
of 1024 samples per buffer? The phones are the OKTA (HTC) Touch and the HTC
Titan, both running WM6.

Robert Scott
Ypsilanti, Michigan

From: Robert Scott on 16 Jun 2008 15:32
OK, now I have two customers complaining about the same problem with the HTC
Touch phones. Is there anyone who can verify this problem?


On Fri, 13 Jun 2008 14:24:17 GMT, ---@---.--- (Robert Scott) wrote:

>We have received a report of a peculiar problem with the HTC Touch PDA/phone
>from one of our customers. He has tried our audio spectrum analysis software on
>three different units, and on each unit, our Fourier spectrum display, when
>listening to a pure sine-wave tone, shows not just a single peak from the FFT
>analysis, but it shows the central peak surrounded by sidebands spaced every 11
>Hz or so. To me this sounds like phase modulation, such as you would get if the
>audio samples had a periodic phase discontinuity.
>
>We sample continuously at 22050 samples per second using multiple buffers of
>1024 samples per buffer. This comes out to 21.53 buffers per second - close to
>double the reported spacing in the sidebands. I hypothesize that our buffers
>are not getting filled by the system audio drivers with 1024 samples of
>continuous data. If the drivers happened to drop a few samples from one buffer
>to the next, that would result in exactly the kind of phase modulation that our
>Fourier analysis is indicating.
>
>Does anyone know if there are any reported audio problems that would affect a
>listening program that samples at 22050 samples per second and uses 16 buffers
>of 1024 samples per buffer? The phones are the OKTA (HTC) Touch and the HTC
>Titan, both running WM6.
>
>Robert Scott
>Ypsilanti, Michigan
>

Robert Scott
Ypsilanti, Michigan

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