EZ CD Extractor - Output vs input bit rate

[RhoXS]

I just purchased an iTunes Plus song (Stones - Bitch). I then used EZ CD-DA Extractor 10 to convert it to mp3 format.

Original file: 6,991 KB m4a @ 256 kbps (as downloaded)

Output file: 5.244 KB mp3 (CD-Quality specified for output file)
Output file: 6.945 KB mp3 (256 kbps specified for output file)
Output file: 8,646 KB mp3 (320 kbps specified for output file)

Does this imply "CD Quality" uses a bit rate less than 256 mbps?

I would have assumed "CD Quality" would have resulted in an output file much larger than the 256 kbps input file.

In other words, what output bit rate will retain all the quality of the original m4a file but not unnecessarily increase the output file size?

Specifying an output bit rate equal to the input file bit rate produces a file almost identical in size. Can I accurately assume the out put file will not be degraded in this case?

[SallyDog]

I don't believe ANY bitrate will retain the original quality as you're going from one lossy format to another.

[RhoXS]

I am trying to determine what bit rate will retain the most of the quality available in the original m4a file, recognizing there will probably be some unrecoverable but inconsequential loss.

Now that you made me think about it, what is the difference between the m4a and mp3 formats?. Is the encoding different or does the difference simply manifest itself as variations in headers, etc.? If the encoding is essentially the same, then maybe there will not be any real loss during the conversion.

[SallyDog]

I'm not the person to ask for the technical differences, but I will say this - regardless of how much "quality" may or may not be lost, the only thing that really matters is how much of it your ears can perceive. Nothing else is of any relevence (IMHO!)

[tebasuna51]

I am trying to determine what bit rate will retain the most of the quality available in the original m4a file, recognizing there will probably be some unrecoverable but inconsequential loss.

The answer is easy: to retain the max quality use the max bitrate.

Now that you made me think about it, what is the difference between the m4a and mp3 formats?. Is the encoding different or does the difference simply manifest itself as variations in headers, etc.? If the encoding is essentially the same, then maybe there will not be any real loss during the conversion.

The m4a, or mp4 with only audio, is, normally, a container with AAC audio (http://en.wikipedia.org/wiki/Advanced_Audio_Coding), then is a different format and more efficient than mp3 at low bitrates.

For high bitrates, like 256 Kb/s for stereo, is difficult listen the differences.