MadSci Network: Engineering

Re: What audio effects result from the use of merging bits in CD encoding?

Date: Tue Jan 2 05:11:05 2001
Posted By: Bruno Putzeys, Staff, Electroacoustics and Analog Electronics, Philips ITCL
Area of science: Engineering
ID: 976251114.Eg


Actually, the process is referred to as "eight to fourteen modulation" 
(EFM) in which 8-bit words are recorded as 14 bit words with no less than 
3 and no more than 11 consecutive "1"s or "0"s.
This means that there is a fixed ratio between the incoming and the 
outgoing bit rate so this process is of no influence to the stability of 
the clock (which would be the only way to influence the sound quality).
For more on clock stability, read my reply to question no. 976251114.Eg
The EFM scheme was invented to make use of the property that pit length 
differences can be read to much shorter lengths than the shortest pit, 
packing more data per area without any loss of data reliability.



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