tr[\x00-\xff][
\x00UT\x01P\x05\x04 Q(\x15\x14)\x10ED\x11
\x00UT\x01P\x05\x04Q(\x15\x14)\x10ED\x11
\x00UT\x01P\x05\x04Q(\x15\x14)\x10ED\x11
\x00UT\x01P\x05\x04Q(\x15\x14)\x10ED\x11
\x00UT\x01P\x05\x04Q(\x15\x14)\x10ED\x11
\x00UT\x01P\x05\x04Q(\x15\x14)\x10ED\x11
\x00UT\x01P\x05\x04Q(\x15\x14)\x10ED\x11
\x00UT\x01P\x05\x04Q(\x15\x14)\x10ED\x11
\x00UT\x01P\x05\x04Q(\x15\x14)\x10ED\x11
\x00UT\x01P\x05\x04Q(\x15\x14)\x10ED\x11
\x00UT\x01P\x05\x04Q(\x15\x14)\x10ED\x11
\x00UT\x01P\x05\x04Q(\x15\x14)\x10ED\x11
\x00UT\x01P\x05\x04Q(\x15\x14)\x10ED\x11
\x00UT\x01P\x05\x04Q(\x15\x14)\x10ED\x11
\x00UT\x01P\x05\x04Q(\x15\x14)\x10ED\x11
\x00UT\x01P\x05\x04Q(\x15\x14)\x10ED\x11
];
[download]

Okay. I took your spec and coded this slow and labourious implementation and applied it to the bytes 0 .. 255:

#! perl -slw
use strict;
use Data::Dump qw[ pp ];

my %map;

for my $i ( 0 .. 255 ) {
    my @Q;
    my @D = split '', unpack 'b8', chr $i;
    $Q[ 0 ] = $D[ 0 ];
    $Q[ 1 ] = $D[ 1 ] ^ $Q[ 0 ];
    $Q[ 2 ] = $D[ 2 ] ^ $Q[ 1 ];
    $Q[ 3 ] = $D[ 3 ] ^ $Q[ 2 ];
    $Q[ 4 ] = $D[ 4 ] ^ $Q[ 3 ];
    $Q[ 5 ] = $D[ 5 ] ^ $Q[ 4 ];
    $Q[ 6 ] = $D[ 6 ] ^ $Q[ 5 ];
    $Q[ 7 ] = $D[ 7 ] ^ $Q[ 6 ];
    my $outb = ord pack 'b8', "@Q";
    $map{ $i } = $outb;
}

pp \%map;
[download]

And it produced this output:

<Reveal this spoiler or all in this thread>

That's a byte to byte mapping table. I then used that to build the translation table I posted.

---

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

"I'd rather go naked than blow up my ass"

A couple of points I don't understand about Re^7: encoding hdmi video byte.

First, in the statement
    my $outb = ord pack 'b8',"@Q";
will not  "@Q" interpolate the array with spaces between the elements of  @Q and so give an oddball result (i.e., only 16 unique values) since a space (ASCII space == 0x20) is packed by b as a 0 bit and half the elements of  @Q will be ignored?
I.e., shouldn't it be
    my $outb = ord pack 'b8',join '', @Q;
instead?

The other point I don't understand is that I took the OP statement

Data byte D(0:7) encode this to make 9bit data q_m(0:8)
q_m[0] = D(0);
q_m(1) = q_m(0) XOR D(1);
q_m(2) = q_m(1) XOR D(2);
q_m(3) = q_m(2) XOR D(3);
q_m(4) = q_m(3) XOR D(4);
q_m(5) = q_m(4) XOR D(5);
q_m(6) = q_m(5) XOR D(6);
q_m(7) = q_m(6) XOR D(7);
q_m(8) = 1;
[download]

to be pseudo-code, and to be the equivalent (on a byte-for-byte basis) of

$q_m_byte = (0x100 | ($D_byte ^ (0xff & ($q_m_byte << 1))));
[download]

with a  $q_m_byte 'byte' of 9 bits always ending up with its bit-8 set, and bit-7 of the original value of  $q_m_byte always being lost.

But

$Q[ 0 ] = $D[ 0 ];
$Q[ 1 ] = $D[ 1 ] ^ $Q[ 0 ];
$Q[ 2 ] = $D[ 2 ] ^ $Q[ 1 ];
$Q[ 3 ] = $D[ 3 ] ^ $Q[ 2 ];
...
[download]

seems to be the equivalent of

$Q[ 0 ] = $D[ 0 ];
$Q[ 1 ] = $D[ 1 ] ^ $D[ 0 ];
$Q[ 2 ] = $D[ 2 ] ^ $D[ 1 ] ^ $D[ 0 ];
$Q[ 3 ] = $D[ 3 ] ^ $D[ 2 ] ^ $D[ 1 ] ^ $D[ 0 ];
...
[download]

which is very different.

Thanks a lot! Mr. BrowserUK.... that is really a ery big help !!!!