shirriff@sprite.berkeley.edu (Ken Shirriff) (05/14/91)
I've determined the algorithm for the first 100 codes. I wrote a C program
to decode a code from 1 to 99. To use this, run "code 42 3" to determine
what happens with code 42 in March.
The first 100 codes correspond to channels 1-4 recording 30 minutes on
a fixed set of 8 times for the 1st to the 3rd of the month.
The first 1000 codes extend the same times and channels for the rest of
the month, but I haven't decoded that yet.
Let me know if you find any errors with this program.
Also, if there's a VCR+ mailing list, can someone add me to it?
/*
* Copyright 1991 Ken Shirriff shirriff@sprite.Berkeley.EDU
*/
char *tn[8] = { "6:30", "4", "7:30", "4:30", "3:30", "5:30", "6", "2:30"};
main(argc,argv)
int argc;
char **argv;
{
int num, month;
int result, day;
int time, chan;
if (argc != 3) {
printf("usage: code num, month\n");
exit(-1);
}
num = atoi(argv[1]);
month = atoi(argv[2]);
code(num, &result, &day);
result = (result+day*month)&31;
time = ((result&16)>>2) | ((result&4)>>1) | (result&1);
chan = (((result&8)>>2) | ((result&2)>>1))+1;
printf("Code %d in month %d = %s, ch %d on day %d\n", num, month,
tn[time], chan, day);
}
code(num,result,day)
int num, *result, *day;
{
int row, col, rem, div, d;
int res;
/*
* Break up into 7 rows of 5 columns on 3 days.
* The numbers are broken mod 29 and then broken in half again unevenly.
*/
rem = num%29;
div = num/29;
if (rem<16-div) {
row = 3-div;
} else {
row = 6-div;
rem -= 13;
}
col = 4-(rem-1)/3;
d = ((rem-1)%3)+1;
/*
* The numbers are then assigned consecutively down the columns.
*/
res = col*7+row;
/*
* Swap numbers 1-9 with row 3
*/
if (num<=9) {
res = num;
d = 1;
} else if (d==1 && res<=9) {
col = 4-(res-1)/3;
d = ((res-1)%3)+1;
row = 3;
res = col*7+row;
}
*day = d;
*result = res;
}
Ken Shirriff shirriff@sprite.Berkeley.EDUjfr@locus.com (Jon Rosen) (05/15/91)
In article <1991May14.074739.3646@agate.berkeley.edu> shirriff@sprite.berkeley.edu (Ken Shirriff) writes: >I've determined the algorithm for the first 100 codes. I wrote a C program >to decode a code from 1 to 99. To use this, run "code 42 3" to determine >what happens with code 42 in March. > >The first 100 codes correspond to channels 1-4 recording 30 minutes on >a fixed set of 8 times for the 1st to the 3rd of the month. > >The first 1000 codes extend the same times and channels for the rest of >the month, but I haven't decoded that yet. > ><stuff and program deleted> Ken, please don't take these a flames, just gentle chiding! :-) But really, what is the point? Get a life, man! I hope who are doing this just as an intellectual exercise... (Why do you climb Mt. Everest? Because it is there! Why do you decoed VCR+ codes? Because they are there!) First of all, the codes are printed in the newspaper right where the times and channels of the programs are. I.e., you know exactly all the information you need to know to program you VCR. Anyone who can write a C program that is as good as the one you wrote can not possibly need something as dunce-like as the VCR+ to program their VCR! Second, without the VCR+ equipment, the codes themselves are useless! Third, if you wanted to build your own "dunce programmer" like the VCR+ for yourself, you could use your own coding scheme (forget theirs!) Finally, if you want to build a programmer to compete with theirs using their coding scheme (so you can get the benefit of the printing in the TV Guides of the numbers), good luck and watch out. I believe they have patented their coding scheme and it will probably hold up so you will be violating their patent if you use their codes comercially. Second, I doubt you can sell it for less than $60 - their current price - and make much money at it even if you do not get into patent trouble with them. What I want to see is a disk distribution of television program information with a hookup to a VCR remote programmer and a neat easy to use menu system for selecting shows. That would really be slick and might put to use those million or so "home" computers that Tandy and IBM are selling at under $1000. People pay for their cable usage. Would they pay, oh, say about $5 a month more to get a complete monthly program guide on disk (or on-line?) Maybe they would and at that price, if you could get over 5000 subscribers, it would be a pretty neat small business. :-) Jon Rosen :-) (Smileys quite sincere!)