I am a recording artist and have an extensive background in audio engineering.
As a preface: We all know that Premiere Pro converts what ever audio you import to 32 Bit-float audio because it is better to do changes to audio at this Bit depth due to a decreased amount of "rounding errors."
I have a master recording of a song in a format of 44.1kHz Sample Rate 32 Bit-float Bit Depth BWF file.
Next, I used iZotope RX to change the sample rate of the file to 48kHz and retaining the 32 Bit-float Bit Depth. iZotope RX has a SUPER high quality sample rate converter, rivaled only by Weiss Saracon. My audio geeks feel me on this here. Belive it or not, but Pro Tools and Logic Pro X have AWFUL sample rate converters. Google SRC infinite wave sample rate conversion comparison.
So now the file is 48kHz 32 Bit-float.
The next thing I did was send this file to my music video director for editing.
The video will be uploaded to YouTube, which as far as I know does not accecpt 32 Bit-float audio?? (correct me if I am wrong, I really want YouTube to accpet 32 Bit-float audio becuase going from 32BF to AAC sounds better than going from 16bit or 24bit to AAC).
The big quesiton is: should I tell the music video director to have the video's audio exported as 48kHz 24 Bit, knowing that Premiere Pro/Media Encoder will dither from 32 Bit-float to 24 Bit? (YES YOU NEED TO DITHER FROM 32BF TO 24BIT, READ BOB KATZ'S BOOK LOL) OR Should I add dither to the 48kHz 32 Bit-float file and when he exports it as 48kHz 24 Bit it will already have the proper dither in place to smooth out that wordlength truncation.
IF YOU DONT WANT TO READ THE ABOVE:
DOES PREMIERE PRO ONLY TRUNCATE FROM 32BITFLOAT TO 24 BIT OR 16 BIT OR DOES IT ADD DITHER THEN TRUNCATE WHEN EXPORTING 32BITFLOAT AUDIO TO 24BIT OR 16BIT AUDIO?
I cannot find and dither settings or and mention of dithering audio on ANY adobe manuals or anything.
you could have him send you the XML of the edited footage and re-sample the audio in izotope yourself if you were that worried about it since I don't think youtube supports 32bit audio. but if if an adobe engineer doesn't pop in here, just make a 32 bit white noise in izotope and compare against adobe media encoder. for downsampling, you should see dither in both.