#!/bin/bash
# 16to8bit_new.sh
> /tmp/sample.raw
> /tmp/leftbinary
> /tmp/signed16bit.txt
dd if=/dev/urandom of=/tmp/sample.raw bs=1 count=192000 > /dev/null 2>&1
od -td2 -An /tmp/sample.raw > /tmp/signed16bit.txt
awk --characters-as-bytes 'NR%2 { printf("%c", (($1+32768)/256)) > OUT }' RS="[ \r\n\t]+" BINMODE=3 OUT="/tmp/leftbinary" /tmp/signed16bit.txt

Last login: Sun Nov  2 13:30:37 on console
AMIGA:barrywalker~> cd Desktop
AMIGA:barrywalker~/Desktop> cd Code
AMIGA:barrywalker~/Desktop/Code> cd Awk
AMIGA:barrywalker~/Desktop/Code/Awk> ./16to8bit_new_c688.sh
awk: extra ) at source line 1
 context is
	NR%2 { printf("%c", >>>  ($1+32768)/256)) <<< 
awk: syntax error at source line 1
awk: illegal statement at source line 1
	extra )
AMIGA:barrywalker~/Desktop/Code/Awk> ./16to8bit_new_c688.sh
AMIGA:barrywalker~/Desktop/Code/Awk> ls -l /tmp/leftbinary
-rw-r--r--  1 barrywalker  wheel  1  2 Nov 13:39 /tmp/leftbinary
AMIGA:barrywalker~/Desktop/Code/Awk> _

#!/bin/bash
# 16to8bit_new.sh
> /tmp/sample.raw
> /tmp/leftbinary
> /tmp/signed16bit.txt
dd if=/dev/urandom of=/tmp/sample.raw bs=1 count=192000 > /dev/null 2>&1
od -td2 -An /tmp/sample.raw > /tmp/signed16bit.txt
awk --characters-as-bytes '
{
	BINMODE=3;
	FS=" ";
}
{
	if ($1=="") exit(0);
	$1=(int(($1+32768)/256));
	$3=(int(($3+32768)/256));
	$5=(int(($5+32768)/256));
	$7=(int(($7+32768)/256));
	printf("%c%c%c%c",$1,$3,$5,$7) > "/tmp/leftbinary";
}' < /tmp/signed16bit.txt