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View Diary: How Many Former NSA and FBI Counterterrorism Employees Will It Take For This Story To Reach The MSM? (140 comments)

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  •  You done trolling my post with bullsh*t yet? (7+ / 0-)

    I won't waste my time refuting this last comment, but I will say it's grossly incorrect.

    "I always thought if you worked hard enough and tried hard enough, things would work out. I was wrong." --Katharine Graham

    by bobswern on Mon May 20, 2013 at 03:04:06 PM PDT

    [ Parent ]

    •  20 min. phone call =data file less than 100Kb (1+ / 0-)
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      jrooth

      Please read WolfmanSpike source comment.

      The phone company does not use PCs to digitize and store audio data.  
      It appears to me that none of you actually know how the phone company digitizes the audio signal because, based on the comments so far it seems to me that folks here believe the phone company uses the same techinques PCs and Macs use to do this task.  Because PCs and Macs do it does not mean that it is the ONLY way it can be done.   It is as if anytime "data" is mentioned anywhere it has to relate to PCs and how they work, or the Internet and how it works.  There were techniques of doing things with digital data LONG before both PCs and the Internet existed.  Techniques well established.  Embedded solutions that have nothing to do with PCs and how they handle and compress data.  There is more to the digital electronics world than PCs, the Internet and the cell phone.

      The phone system does not use the same audio codecs, digitization or compression PCs and Macs use (although more modern PCs and MacOS may have software and hardware capable of decoding these techinques).  The phone company uses a technique known as CVSD (Continuously Variable Slope Delta Modulation) and more modernly, ADM (Advanced Delta Modulation). These schemes of digitization are capable of creating a serial data stream at the same data rate as the bandwidth of the input signal without having quantization issues.  So if the phone line is limited to a 3KHz signal (which it is) then the sample rate can be as low as 3KHz and still maintain signal integrity (although the phone company often samples at much higher rate to accompany modem FSK (Frequency Shift-Key) and provide better quality audio).

      Using this as a foundation, if the phone signal is limited to 3KHz and anti-aliased to 2KHz then it would take 3000 samples per second, yielding  180,000 samples per minute or 3.6M samples in a 20 minute call.  Remember that CVSD creates a SERIAL data stream so this would compress to only 450K 8-bit bytes.  Once compressed using standard compression this results in a data file less than 100K in size.

      "We are a Plutocracy, we ought to face it. We need, desperately, to find new ways to hear independent voices & points of view" Ramsey Clark, U.S. Attorney General.

      by Mr SeeMore on Mon May 20, 2013 at 08:12:45 PM PDT

      [ Parent ]

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