# resulting SIZE of audio file based on encoding followed by compression

I wish to know if I have a correct understanding of how the way in which audio is encoded and then compressed determines the size of the resulting compressed file.  Here is an example of what I think occurs.

Suppose a 240 second song is encoded digitally with a sampling rate of 44.1kHz.  Then suppose that 16 bits are used to encode each "frame".  This would result in 44,100 x 16 x 240 / 8 = 21,168,000 bytes of data.  Thus this example song would require 21.168 mb uncompressed when stored on an audio CD.

Next compress the roughly 21 mb file using a bitrate (assumed constant) of 128 kbits per second.  This will be a function of the 240 seconds and the bitrate only, ignoring the size of the uncompressed file.  I.e, I assume the 16 bits used for each "frame" during the encoding as well as the sampling rate are transparent to the compression process.  So, the compressed file's size will be 240 x 128,000 bits / 8 = 3,840,000 bytes.  Then this 3.84 mb is a typical file size for, say, an mp3 file holding a 4 minute song.

If I am correct with this example, great.  If not, I would appreciate finding where I misunderstand this.

thanks,
whr

###### Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

x
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Commented:
The operative word here is "audio CD". They don't use wave files, they use PCM. And you can't mess with the compression or the bitrate in any way on the Red Book audio standard for CDs. The standard is 44.1K 16bit 2 channel PCM.
0
Author Commented:
Sorry,

I am a "beginner".  I don't understand the response.

Perhaps I should point out that I wasn't suggesting that my encoding scenario was correct in the sense that this is the way it is actually done in a studio.  I just want to know if this would be a correct determination of the final file size for a hypothetical song after encoding and then compressing using these hypothetical parameters.

thanks,
whr
0
Commented:
Probably best to wade through the Wikipedia for a technical analysis of the terms:
Bitrate
Sampling Rate
Red Book Audio
Compression Ratio
etc...

0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

###### It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Multimedia Programming

From novice to tech pro — start learning today.