Trying To Save MP3 16-Bit But Always Saves As 32-Bit Float

[cdcollura]

When I edit wave / MP3 files in Adobe Audition, Build 24.4.1.3 ... I convert it to 44.1 Khz (sample rate doesn't matter) and from either 8 bit (or 32 bit) to 16-bits, and save it ... If I exit and re-load it into Audition it's 32 Bit float (sample rates are correct, just not the 16 bit depth). I even loaded a saved file into VLC and it's also says 32 bits.

Steps To Repeat:

1. Load an audio file, convert it to, or make sure it is 16-bit audio (ss1.png).

2. Save-As, make sure it's 16-bits, mp3. I used "Test.mp3" in this example.

3. Look at the file in another program, such as VLC, and it's 32 bits (ss2.png).

4. Re-load it (open) and it's 32-bit float (ss3.png).

[Richard M Knight]

I'm seeing the same here. 

[Richard M Knight]

Just had a quick Google, as I understand it MP3s don't have a bit depth only a bit rate, the depth reported seems to depend on the decoder.

[SteveG_AudioMasters_]

Actually it's very simple - when Audition re-opens any compressed format file at all, it is decoded into a 32-bit format. If you want to find out definitively what the format of a stored file is, you have to look at its preferences in your OS. And no, this is not a bug.

[cdcollura]

Not sure about that. Before if I saved in 8 (or 16) bits and reloaded it, it was "as if it was saved", 8 or 16 (not 32 regardless). Remember I also used VLC and checked the encoding of the file I saved in Audition, and it was 32 bits. Before that, the 16 bit file also showed 16 bits in VLC.

[SteveG_AudioMasters_]

No it really is very simple, and you can check it yourself easily. If you create an MP3 file in Audition, re-open it aand look at its properties, you'll find that they will display the files's properties as you saved them, and the same thing will be displayed in the metadata. But if you look at the bottom right corner of the screen, it will show you the properties of the file as Audition re-opened it, and that will say that it's been opened as a 32-bit file.

[cdcollura]

That's what I have been doing as well. It's 32 bit in the properties as well. Only for MP3, the WAV one is correct.

[excited_genius9689]

Agree that this does look like a bug in the "Save As" conversion to an mp3. While I agree with the (prolific and super helpful) SteveG on how Audition handles the opening of assets, I'm seeing cdcollura's behavior represented on files I've tried with verifications in VLC and FFMPEG showing a 32-bit float coming back instead of a 16-bit getting asked for in the save. It might not be a problem for all users in terms of a file's usability, but it's definitely not working as Audition intends. If Audition wants to push the notion forward that an mp3 has no bit depth and just a bitrate, then bit-depth options should be made unavailable for that codec setting. But I would agree that the behavior of legacy Audition and the current versions are quite different in this regard.

[SteveG_AudioMasters_]

Still don't think it's an actual bug - it's as designed (even if you don't like it). Whatever format and bit depth an MP3 is when it's encoded doesn't matter, when Audition is going to decode it as 32-bit anyway. So effectively the original MP3 retains its assets so the file name remains - as does the file itself. It's only what happens to it in Audition that you see (apart from the admittedly slightly misleading indications around the screen real estate).

It's also worth noting, if you haven't noticed it already, that Audition isn't using the Fraunhofer encoder any more, now that the copyright has expired - it's using Lame. Don't think that makes any difference to the file handling though.

[excited_genius9689]

I appreciate that from a decode side, my perspective is that the issue is in Audition's conversion process. If one has a straight WAV and lossy compresses it to a 320k MP3, one is provided optionality for different bit depth, with a presumption that the bit depth chosen would be correctly read in the data header by outside of Audition places (VLC and FFMPEG aren't exactly unknown quantities in that space). Along those lines your well-made point on LAME might actually have something to do with price of milk here, but would have to dig in on it a little. Thanks for your thoughts.

[excited_genius9689]

just a little more color - I agree that an mp3 isn't a reference format, and therefore a wrapper for 16-bit vs 32-bit doesn't "matter", per se. But, Audition should then remove the wrapper depth as an option for conversion. If it's irrelevant, don't show it to the user.