[hpsdr] Audio distortions during zoom/pan panadapter

[ghbyrkit at chartermi.net]

	I did a little more digging. SysInternals has a tool that shows the
timer resolution. It's called ClockRes.exe, and is available at the
URL:

	https://technet.microsoft.com/en-us/sysinternals/bb897568.aspx [1]

	You could run it without having the DPC checker running, then run the
DPC checker and run again, and note/report any differences. It's also
possible that running the Media Player would get a similar result.

	The SysInternals page says that there is a fine document discussing
how to change the system timer resolution at:

	https://technet.microsoft.com/en-us/sysinternals/bb897569 [2], but
that link doesn't seem to go anywhere useful.

	StackOverflow has some info at:
http://stackoverflow.com/questions/3744032/why-are-net-timers-limited-to-15-ms-resolution
[3]

	There is possibly other information on the NT Kernel functions
NtSetTimerResolution and NtQueryTimerResolution that a program could
use to get better resolution, if that makes things work better.

	73,

	George K9TRV

	-----------------------------------------From: "Roger Rehr W3SZ" 
To: 
Cc: 
Sent: Wed, 9 Dec 2015 13:30:01 -0500
Subject: Re: [hpsdr] Audio distortions during zoom/pan panadapter

 I had the same thought as George, namely that the issue is one of the
granularity of the windows default timer. 

 I had a similar issue years ago [2007] when playing around with the
Delphi IDE, and wrote a bit about it then.
 http://www.nitehawk.com/w3sz/windowstimingissues.htm [4] 

 I believe that you can prove the diagnosis as follows:

 There is a program named skedgran01.exe that runs on Windows versions
up to and including Windows 10 that shows you the timer granularity
for your system under default and high resolution timing. This is the
first link on my webpage.

 You can run skedgran01.exe [testing the "DefaultTiming"] both when
you are running DPC Checker and when you are not, and see if in fact
the timer granularity is affected, as George suggested, by the DPC
Checker. It is my assumption that it will be affected.

 I just checked to make sure all of this works on Windows 10, and it
does EXCEPT that DPC Checker won't run on Windows 10 here, even with
compatibility modes, and so I need to leave the last check to you as
outlined above.

 The images below will give you an idea of what to look for
[substitute "With DPC Checker" for "With YahooFinance"]:

 See the skedgran01.exe result here for Default timing 
 With: http://www.nitehawk.com/w3sz/DefaultTimingWithYahooFinance.png
[5]
 and
 Without: http://www.nitehawk.com/w3sz/DefaultTimingBaseline.png [6]
 the Yahoo Finance page opened.

 Compare this with high resolution timing result
 With:
http://www.nitehawk.com/w3sz/HighResolutionTimingWithYahooFinance.png
[7]
 and 
 Without:
http://www.nitehawk.com/w3sz/HighResolutionTimingBaseline.png [8]
 the Yahoo Finance page opened.

 Also note that running Default Timing with the Yahoo Finance page
opened is NOT equivalent to running with High Resolution Timing.

 Please post your results back to the list!

 Oh, the Code Project c++ program source given in the Code Project
article linked to from my web page does compile on Win10 using Visual
Studio 2013, and it runs perfectly. But I think using the
skedgran01.exe program as outlined above is a superior approach to
figure out what is going on here.

 Hope the above helps, and

 73,

 Roger Rehr
 W3SZ

  On 12/9/2015 9:02 AM, ghbyrkit at chartermi.net [9] wrote:

	***** High Performance Software Defined Radio Discussion List *****  

	I could be wrong, but I suspect that possibly running the DPC checker
(and various other multimedia software) COULD switch the computer
timing resolution from about 16 ms to 1ms or so, or some other 'high
resolution' value that allows multimedia stuff to behave better
(faster, more responsive, less subject to latency issues) 

	I'm not sure how to check this, but it could explain the results. 

	73, 

	George K9TRV

 

Links:
------
[1] https://technet.microsoft.com/en-us/sysinternals/bb897568.aspx
[2] https://technet.microsoft.com/en-us/sysinternals/bb897569
[3]
http://stackoverflow.com/questions/3744032/why-are-net-timers-limited-to-15-ms-resolution
[4] http://www.nitehawk.com/w3sz/windowstimingissues.htm
[5] http://www.nitehawk.com/w3sz/DefaultTimingWithYahooFinance.png
[6] http://www.nitehawk.com/w3sz/DefaultTimingBaseline.png
[7]
http://www.nitehawk.com/w3sz/HighResolutionTimingWithYahooFinance.png
[8] http://www.nitehawk.com/w3sz/HighResolutionTimingBaseline.png
[9] mailto:ghbyrkit at chartermi.net

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