Thank you very much, Carl!
The 2009 spec for the BEXT chunk was the latest I could find. What I did
find that was that the BWF implementation in Samplitude extended the
sampling frequencies at least to 192000 and the bit depth to 32. This
implementation, and other comments I received, suggest that there is no
differentiation in the bit depth between float and fixed, but I THINK
the vast majority of 32 bit audio is float and not fixed. My install of
Windows File Explorer has a hover-over info box that does show "32 bit
floating point." It also shows the data in the BEXT chunk. This pop-up
info box shows "dbpoweramp" which is 3rd party software I have
installed, not Windows native.
To reiterate, Samplitude used 32 for 32 bit float in the coding history.
Also, thanks for the references to the BWF and RF64 file specs, below. I
don't think they address the content of the BEXT chunk, but I will check.
On 2018-08-08 8:21 AM, Carl Fleischhauer wrote:
> There are newer-than-1999 versions of relevant EBU specs, as reported on the Library of Congress Format Sustainability site (https://www.loc.gov/preservation/digital/formats/fdd/fdd000357.shtml), which itself is a little old in the tooth (last updated in 2012). That formats-page update coincided with the publication of the revised FADGI audio metadata guideline (http://www.digitizationguidelines.gov/guidelines/digitize-embedding.html).
> I have not time just now to look at the newer EBU specs (apologies!) and thus cannot report if they are at all helpful re: sampling frequencies, bit depth, or floating point math. Perhaps another reader will help us out. The bullets below highlight the most obvious aspects of these two specifications.
> From the LC formats web page:
> Format specifications
> • EBU Tech 3285 - Specification of the Broadcast Wave Format (BWF) - Version 2 - (2011) (https://tech.ebu.ch/docs/tech/tech3285.pdf). Version 2 of BWF is a substantial revision that incorporates Loudness Metadata (in accordance with EBU R 128) and which takes account of the publication of Supplements 1 – 6 and other relevant documentation.
> • EBU – TECH 3306: MBWF / RF64: An extended File Format for Audio (2009) (http://tech.ebu.ch/docs/tech/tech3306-2009.pdf). Permits file sizes greater than 4 GB and various types of multichannel audio.
> Best from Carl Fleischhauer
Richard L. Hess email: [log in to unmask]
Aurora, Ontario, Canada 647 479 2800
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