1/19/2008
Copyright
2005 Tim Hoerning
28
Not all bits are created equal
Remember that with PCM, the Most significant bit
determines whether a signal is
above or below the x axis.
An error on this bit will create a large error
The Least Significant Bit however determines which of
two adjacent levels is
selected
An error on this bit will create a barely noticeable
error
Sometimes Errors are intentionally introduced on the
least significant bits to
encode extra information
Robbed Bit Signaling used the Public Switched
Telephone Network (PSTN) to
indicate the status of the switch hook.
The least significant bit
is robbed on every 1 out of 6 frames to encoded this.
Audio Watermarking used as a form of copy protection
on CDs.
Average
of 1 out of 100 bits in error. Position
of error is varied from MSB to LSB
MSB
LSB
