PCMU u-law vs PCMU a-law?

I understand that this codec aka G711 is uncompressed lossless audio quality for phones and is best used through strong wifi connection, but I’m just wondering what’s the difference between u-law and a-law?

PCMA a-law*

emphasis. have you heard of google yet?

Yeah you’re right… I need to stop with these insipid question. Sorry… :frowning:

a-law is common in Europe and u Law in North America. In has vestiges in the framing size or E1’s and T1’s

The difference is meaningless to you. They are both uncompressed linear CODEC’s. While you are googling check out Shannon’s law and you will understand why a 64k linear CODEC only has the frequency response of a voice telephone circuit. Dynamic range (the quantifiable difference between the loudest discernable sound and the softest is a function of the number of bits. )

The only way to increase the dynamic range or Freq. response (Like HD Voice g.722) is to remove information during the quantization process relying on the human ears ability to fill in microscopic missing information. Sometimes it’s a good trade off. g.729 and GSM are both very “listenable” CODEC’s

BTW CODEC stands for COder DECoder - I hope this is intuitively obvious to you.

ONe more thing about low bandwidth CODEC’s. Since more sonic information is transmitted in less data, packet loss and jitter issues are magnified.

Now I love teaching this subject, one that entire books have been written about, my favorite is http://www.amazon.com/Digital-Imaging-Applications-Howard-Burdick/dp/0079130593 while it discusses video the principals are the same. Disclosure, Howard is my Uncle.

But anyway in the 15 minutes while I type this and researched my answers I have become smarter. You, when done reading it will not be much farther. My point of that is when we tell you to Google it’s not out of a cruel streak (though ball busting is fun) the skill to research a subject is crucial for the success of any technologist.

This also was not a FreePBX question.

i always thought that the pre-emphasis de-emphasis (the only real difference in those 64k bits) is because americans speak with melflous voices and europeans with squeaky nasal twangs :wink: