Quality of MP3

[Guest]

I insert the MP3 file as a minus file in Adobe Audition CC 2015. When I want to save the session it says, that some files are out of the session and propose to save a copy. But a saved copy is of much LESS quality as an original MP3! I use 32 bit format for a whole session, 44100 sample rate, but still a big change...

How to preserve the original quality of MP3?

[SteveG_AudioMasters_]

If an MP3 file is opened in a session, and then you save it again as an MP3 then yes, it will be degraded, as it will have been re-encoded to do this. When the file is decoded the first time to a wav file, then you should save this and use it in the session - then it won't degrade. The reason for all of this is that MP3 files are only meant to be used as distribution files, and not for origination, as their compressed format compromises the data significantly.

[Guest]

Don't you know - will the MP3 lose the quality by converting to WAV format before inserting into the session? If not - how do I do this? Is there an option inside Adobe?

[SteveG_AudioMasters_]

When you open an MP3 file into a session, it's automatically decoded to an (uncompressed) wav file - it has to be, as that's the format that multi-track internally works in; 32-bit Floating Point. So your MP3 is decoded to that format. If you save the decoded file in that format, it will open up identically next time you open the session.

The problem only comes if you don't save the decoded version.

[Guest]

Well, I just have figured out, that the loose of quality happens already when Adobe makes a wav copy while preparing the session. Why??

I have compared MP3 from the Media Player and inside the Adobe session (32 bit 44100 Hz). There is a notable difference in quality.

Moreover, it shows that the MP3 file has 16000 Hz and WAV 44100. How can Wav file be of a less quality in that case?

It is a very important issue. I will try to insert MP3 in Sonar LE software to see if it also change the quality.

[Guest]

I have just inserted another MP3 and it was opened without the question of different rate and making a copy. The quality is the same as in Media Player.

What could be a problem with the first MP3, and how could I settle the problem?

[Guest]

I have just tried to insert the MP3 by right clicking on the session window Insert - File and it was done without the lose of quality. I did it before using the option Import in the left Files window and dragging into multitrack area, so may be this was the problem.

Anyway, thanks for the help.