[opendtv] The Challenge
- From: "johnwillkie" <johnwillkie@xxxxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Wed, 23 May 2007 23:23:13 -0700
Sorry for those in text mode: you'll probably need html to make much sense
of this.
System_time
GPS Time Value
UTC Time Value
January 3, 2003 00:03:02 GPS
March 2, 2009 01:45:20 UTC
0xEF2906D2
Preamble: I'll credit you that the system time table's CRC-32 is correct,
the GPS_UTC_offset is correct, the daylight savings time value is correct
and the MPEG-2 and ATSC table header is correct. Just fill out the
following bytes, and include all your math.
Step 1: Using just the GPS time value in the table above, create the
system_time bytes for a system time table. (You might want to give up when
you realize that it can't be done with the information provided.)
Seep 2. Using just the UTC time value in the table above, create the
appropriate byte values to represent that time below. (This one is quite
doable.) Remember to include all of your math.
Step 3. Using just the system_time value in the table above, create the
appropriate byte values to represent that time span value in the table
below. (This one just requires a bit of parsing and copying.)
Lesson: the trick is getting the right time value: either UTC, or another
time value plus an integer that corrects that time value to its UTC
equivalent. UTC requires only UTC; GPS or other time bases require the time
and a time offset. Here's another help: At Jan 6, 1980 00:00:00 UTC, GPS
displays said Jan 6, 1980 00:00:07.
STT system_time value bytes
Iteration
Index 0 (system_time_msb)
System_time_lsb
GPS_time value
UTC time value
System_time
Step 4. Now, convert all the various values into their appropriate UTC and
GPS values. For this purpose only, you may assume that the GPS_UTC_offset
is equal to 0. Include all your math, and compare the results to the values
you started with. You have either achieved mathematical proof, or not.
System_time
Time Value
From GPS
From UTC
From system_time
Step 5. Prove to me that the FCC permits use of the procedure in step 1 to
put the time value into system time tables, win $100. This was Bert's
initial assertion.
Step 6. Prove to me that the FCC REQUIRES the use of the procedure in step
1 to put the time value into system time tables, win another $100. This was
John Shutt's 'correction' to Bert's initial assertion.
All submissions become the sole property of John Willkie.
It's just that 'easy.' to WIN! You may already be a winner! Contest only
open to Bert and John Shutt, unless there are others who think they have a
deeper understanding of this that do I.
John Willkie
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