On 24/02/2015 13:55, John N1ISA wrote: > Joe/Bill/Developer's, Hi John, > > Yesterday, I did a clean install of my OS, and then did a new build of 1.5.0- > devel. When I start WSJTX for the very first time, I immediately go to the > "Settings" tab to select, and input my user parameters. I then adjust the > Wide Graph parameters, and almost always adjust the audio input slider last. > As a result, my Wide Graph is always bright red, reflecting the over driven > state coming from my audio input. > > Yesterday, the new FFT Wisdom calculation/calibration was invoked > automatically during my WSJTX user parameters setup routine. > > Does the over driven stated of my audio into the decoder, effect the quality > of FFT Wisdom calculation/calibration? No. > > Does the decoder ignore the audio input stream, and just do mathematical > calculations, and my misadjustment of the audio has no impact on the quality > of the automatic calibration procedure? Not even mathematical calculations really. The FFT wisdom is only based on the size and type of the FFTs calculated and the address of the buffers containing the input and output data in memory.
The calculation is trying to find the most efficient route to a fast FFT by trying different CPU instructions and divide and conquer strategies used to do the transforms. Modern CPUs have special complex instructions that can do more than one basic data transfer or arithmetic operation in parallel (see SIMD for details), the FFTW3 library uses a run time heuristic to determine the fastest strategy for our software on your machine. All these calculations and tests are totally independent of the content of the data. > > >From my layman perspective, it does not seem to. Yesterday, I got excellent > decode's. All of varying signal strengths. I even got a -27 dB JT65 decode. > Still, I am wondering if my FFT Wisdom calculation is the best if could, or > should be. We could enable even more exhaustive searches for the best algorithm but empirical tests have shown the the gain from an even longer search is diminishingly small for the size type and frequency of FFT calculations used in WSJT-X. > > 73, John, N1ISA 73 Bill G4WJS. ------------------------------------------------------------------------------ Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ _______________________________________________ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
