unwanted automatic conversion to 32-bit when exporting/saving

[voiceoverbrian]

I'm using the Beta version of Adobe Audition and saving my work as 44,100Hz 16-bit files. But every time I open a file that I've saved with these specs, it's showing up as 32-bit. It doesn't matter whether I "save as" and change the sample type (overwriting the previous version), or whether I "convert sample type" and then save; every time I then close the file and then re-open it later, it's back to 32-bit.

Any idea why this is happening?

Thanks!

[Richard M Knight]

Open the file using 'MediaInfo' https://mediaarea.net/en/MediaInfo and see what it says.

As I understand it any file imported into Audition is converted to 32bit float for editing.

[voiceoverbrian]

Thanks Richard.

I just noticed that the problem is only happening for mp3 files; i.e. when I open an mp3 file that was saved as 16-bit, it opens as 32-bit, but when I open the original 16-bit wav file from which the mp3 was copied, the wav file opens properly as 16-bit.

When I test both the original wav file and the mp3 copy using MediaInfo (the online version, not the download), I get different information:

1) For the wav file, I get a row listing the bit depth, which is 16. I also get a row for the bit rate mode (constant) and the bit rate (705.6kb/s).

2) For the mp3, I get rows for bit rate mode (constant) and for bit rate (192 kb/s), but there's no row listing bit depth.

So I guess this hasn't really solved the mystery...

[SteveG_AudioMasters_]

Audition doesn't open MP3 files directly - it has to decode them. This is because it only operates using wav files, so MP3s have to be decoded first, and this is always to 32-bit files so that for instance, you can make amplitude changes to them without incurring massive bit depth losses. When you re-encode, the parameters that you specify for the MP3 are adhered to. So basically your observations are correct, but that's the reason for the behaviour. This behaviour was decided upon quite deliberately, in an attempt to minimise the damage done to MP3 files when opened by Audition. 

The damage happens, simply because there's a decode/re-encode process invoked every time you open and save an MP3, and that's unavoidable with lossy files. The losses to a file get greater each time you do it. Ultimately if you go through this process enough times, they'll end up sounding sort-of 'plastic-y', which is not good at all. There are one or two MP3-specific editors available, but what you can do with them is very limited, because of the way the format works. What it comes down to is that you can make rather crude cuts, and vary the volume a little, but that's about it without a full decode.

[voiceoverbrian]

Ah! I see - thank you Steve, that makes perfect sense.