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<DIV>Sort of agree on both points.</DIV>
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<DIV>The BooyaSDR works on raw RF samples from a single ADC, not audio
samples. However, without compression (lossless or lossy), any file of raw
data samples will be of the same size, independent of what values of those
samples. Whether an audio file has NO sound, or full volume sound (to the
ADC’s limits), the file size will be the same – given the bit resolution, sample
rate, and length of recording. Number of channels does also affect the
file size as a multiplier, but I was assuming raw RF samples from an SDR, since
that was the subject of my original email.</DIV>
<DIV> </DIV>
<DIV>I did mention that NO (fancy) compression was assumed in my comments, again
as that’s what the SDR discussed produces. Compression can indeed affect
file size. Lossless compression implies that every bit of the original
material can be totally reproduced. Lossy compression provides a more
compressed final product, but every single bit cannot be faithfully
reproduced. For example, with audio file lossy compression,
physco-acoustic (sp) techniques are usually implemented. Such as if there
is a real loud sound, the ear/brain cannot detect low-level changes immediately
before or after that loud sound. There are a lot of other
techniques.</DIV>
<DIV> </DIV>
<DIV>I’m not familiar with similar compression techniques applying to a
single-channel stream of raw RF data samples, but there may be. Lossless
compression, such as used with zip, rar, and other binary file techniques would
certainly work, post recording.</DIV>
<DIV> </DIV>
<DIV>Keep in mind that with the BooyaSDR, a common off-the-shelf computer will
have trouble processing the raw data samples. 100 million samples per
second, 16-bits per second, results in 200 million bytes per second, or 1.6
BILLION (giga?) bits per second. Gigabit Ethernet is not good enough at
that point. I think. My math is not great. Hence the use of
USB-3 (USBss).</DIV>
<DIV>73, Terry, N4TLF</DIV>
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<DIV style="font-color: black"><B>From:</B> <A title=tacos@amrad.org>Phil via
Tacos</A> </DIV>
<DIV><B>Sent:</B> Tuesday, May 30, 2017 1:29 PM</DIV>
<DIV><B>To:</B> <A title=tacos@amrad.org>tacos</A> </DIV>
<DIV><B>Subject:</B> Re: Three new SDRs in the shack</DIV></DIV></DIV>
<DIV> </DIV></DIV>
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style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>Fourth
factor - data compression?
<DIV> </DIV>
<DIV>Phil M1GWZ</DIV>
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<BLOCKQUOTE type="cite">
<DIV>On 30 May 2017, at 18:19, Joe palsa via Tacos
<<A>tacos@amrad.org</A>> wrote:</DIV>
<DIV> </DIV>
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<DIV>Food for thought-------
<P class=qtext_para
style="WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; COLOR: rgb(51,51,51); PADDING-BOTTOM: 0px; PADDING-TOP: 0px; FONT: 14px/21px q_serif, georgia, times, 'Times New Roman', serif; PADDING-LEFT: 0px; WIDOWS: 1; MARGIN: 0px 0px 1em; DISPLAY: block; LETTER-SPACING: normal; PADDING-RIGHT: 0px; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px">The
size of an audio file is determined by three factors: sampling rate, bit
resolution and channel count.</P>
<P class=qtext_para
style="WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; COLOR: rgb(51,51,51); PADDING-BOTTOM: 0px; PADDING-TOP: 0px; FONT: 14px/21px q_serif, georgia, times, 'Times New Roman', serif; PADDING-LEFT: 0px; WIDOWS: 1; MARGIN: 0px 0px 1em; DISPLAY: block; LETTER-SPACING: normal; PADDING-RIGHT: 0px; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px">Let's
take an example audio file which was recorded at 44.1kHz, mono, and 16 bit
resolution. The bit rate for this file is calculated as: 44100 x 1 x 16 =
705,600 bits per second. Divide that 705,600 by 8 and you've got 88,200 bytes
per second. Divide that 88,200 by 1024 and you end up with 86 kilobytes per
second. Multiple that by 60 and you get 5167 kilobytes per MINUTE. Or 5.047 MB
per minute.</P>
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style="WHITE-SPACE: normal; WORD-SPACING: 0px; TEXT-TRANSFORM: none; COLOR: rgb(51,51,51); PADDING-BOTTOM: 0px; PADDING-TOP: 0px; FONT: 14px/21px q_serif, georgia, times, 'Times New Roman', serif; PADDING-LEFT: 0px; WIDOWS: 1; MARGIN: 0px 0px 1em; DISPLAY: block; LETTER-SPACING: normal; PADDING-RIGHT: 0px; TEXT-INDENT: 0px; -webkit-text-stroke-width: 0px"><FONT
size=2 face=Arial>The audio with more activity I would expect to require more
MB.</FONT></P></DIV>
<DIV> </DIV>
<DIV>73's<BR>Dr Joseph Palsa k3wry<BR>ARRL-Virginia Section
Manager<BR>Virginia State Government
Liaison<BR><A>K3WRY@ARRL.ORG</A><BR>804-350-2665<B><BR><BR></B></DIV></FONT></DIV></DIV></BLOCKQUOTE></DIV></DIV></DIV></DIV></DIV></BODY></HTML>