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.

In reply to Re^8: encoding hdmi video byte by AnomalousMonk
in thread encoding hdmi video byte by hdmiguru

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