View Full Version : Difference of CODEC and MODEM

07-01-2002, 09:54 AM
I'm posting this thread coz I'm kinda confused and I think I was mislead by one of my pal...

All I need to know is what is the difference between CODEC and MODEM? Both seems to convert digital signal to analog signal and vice versa.. but why does we use MODEM to connect to the Internet and not CODEC?

Any nice and easy-to-understand example?

Thanks!!! ;-)

07-01-2002, 11:33 AM
The 'Modem" MOdulates and DEModulates a digital signal to stepped (analog) ADPCM (Adaptive Differential Pulse Code Modulation) frequencies. This allows for higher transfer rates on a single DS0 circuit.

This is a hardware conversion.


A "Codec" on the other hand, COmpresses and DECompresses a digital data signal only. No analog involved. It is nothing more than a compression/decompression algorithm tweaked for optimal use with Video or Audio data.

This is a software conversion.

07-01-2002, 06:37 PM
cool.. that made sense... :D

07-01-2002, 08:01 PM
Ok.. now I'm clear about MODEM - hardware and CODEC - software.. But what I've read from a Business Data Communication book is that the definition of CODEC is:

"a device which converts analog data into digital form, then later recovers the original analog data. This is necessary because many places are still serviced by the older analog lines."

I'm perplexed!!! Please clear my mind!


07-02-2002, 12:23 PM
They are confusing terms. They mean MODEM. the term CODEC didn't even come about until the 90's.

And technically, your telephone contains an A/D D/A converter that converts analog frequencies to digital which are then passed by DS0 to the channelbank at your local Central Office. There it's compressed 4:1 using PCM, and then MUX'd onto fiber. If you have DSL, then you have an additional step-- the signal has to go through a DSLAM before being MUX'd up to the 5E.

07-03-2002, 10:34 AM
huh? I thought I was asking about the difference between MODEM and CODEC? How come MUX and DSO is suddenly in the discussion?

I'm really blur now... All I need to know is the REAL and CLEAR difference between MODEM and CODEC.. like, when or where to use MODEM and when or where to use CODEC....

Please help me...

Thank you...

07-03-2002, 10:47 AM
I already gave it to you. I was only providing additional information so you would gain a greater understanding about how things work.

You guys really can't handle too much in your head at once can you?

07-03-2002, 10:49 AM
> You guys really can't handle too much in your head at once can you?

That's right, Sayeh - you're totally baffling to us in everything you do. We bow humbly to your wisdom. Try to keep in mind that most people on this board are teenagers and students - maybe they actually don't understand you immediately - that's no reason to belittle them.

07-03-2002, 11:02 AM
Then izzit MODEM=CODEC?

07-03-2002, 12:56 PM
A codec has a different definition depending on where it's used. In the telecommunications industry, codec can be used to mean coder/decoder (often in the conversion to digital to analog). This is probably what is confusing you and making the fruits head expand (he's really really clever isn't he/she/it?).

07-04-2002, 01:11 AM
CODEC = Coder Decoder
means anything hardware/software which codes/decodes.

A MODEM is also an example of a CODEC...as it codes/decodes your computer's digital signals into a form which can be transmitted over telephone line, so that you can visit this damn good website :)

Although there are many other CODECs...