Filetype issue; Broadcast Wav, RF64 (ProTools and WavLab)

[JohnRichard]

Greetings,

In my job, I digitize media all day long.
I use a Macintosh computer, Audacity version 2.0.5

Using ProTools I export files routienly over 4Gb.
Using the 64-bit wav extension/BWE broadcast wav platform I have no problem importing these files into WaveLab until I export a file over 4Gb. WaveLab will not read the file.

However, Audacity will open these files no matter how large - the same files output by ProTools.
When I have this issue I open the files in Audacity and export as RF64, change the file extension to .wav and then import to WavLab which works fine.

Can anyone tell me why I need to "clean" a file through Audacity in order for WavLab to understand the file?

Why will Audacity open the file perfectly but WavLab not?
Why will WavLab open the RF64 file that is the same file size?

It certainly has to do with either the way ProTools exports the file (header?), or the type of information WavLab is expecting to see (again header/wrapper?)

Can anyone shead any light on this issue?

[Gale Andrews]

Using the 64-bit wav extension/BWE broadcast wav platform I have no problem importing these files into WaveLab until I export a file over 4Gb. WaveLab will not read the file.

You mean BWF. If WaveLab chokes on the file over 4 GB that suggests it thinks the file has RIFF WAVE headers and not RF64 WAVE headers. Perhaps ProTools is not writing strictly correct RF64 headers. RIFF WAVE (and AIFF) are limited to 4 GB (and many applications can't open RIFF WAVE or AIFF above 2 GB).

However, Audacity will open these files no matter how large - the same files output by ProTools. When I have this issue I open the files in Audacity and export as RF64, change the file extension to .wav and then import to WavLab which works fine.

Sorry, but we do not make WaveLab or offer support for it. All we can say is that if you choose "Other uncompressed files" in Audacity, click "Options..." and change the header to "RF64", then the file will have RF64 WAVE headers whether you leave the extension as RF64 or change it to WAV.

Some apps will only play RF64 with WAV extension.

If you wish to compare file headers you can look in a hex editor http://stackoverflow.com/questions/8273 ... or-the-mac.


Gale

[JohnRichard]

Yes, BWF, my apologizes.

And, thank you for your reply - I understand that you do not produce nor support other software. Let me try to rephrase my question.

How does Audacity deal with large file sizes in wrappers that may not necessarily support large file sizes?
Has Audacity been programmed to cope with things outside the norm?

[steve]

The 4 GB size limit is a consequence of 32 bit header information. At 4 GB, 32 bit runs out of numbers needed to keep track of all of the samples - basically it is an addressing problem. If a WAV file has 64 bit headers, it can be very much longer than 4 GB. Although Audacity does not fully support BWF, it is able to read 64 bit headers, and can therefore support WAV files with 64 bit headers that are over 4 GB. Your question is really one for WavLab - why can't their program open WAV files that have 64 bit headers?

[Gale Andrews]

How does Audacity deal with large file sizes in wrappers that may not necessarily support large file sizes? Has Audacity been programmed to cope with things outside the norm?

No. If you import a RIFF WAV file into Audacity that is over 4 GB Audacity will truncate it, from what others have said (unless you import it as Raw Audio in which case the headers are ignored).

Your files therefore almost certainly have RF64 headers in the first place. As I said, you can examine the headers in a hex editor if you are curious.


Gale

[steve]

A couple of informative articles:
http://en.wikipedia.org/wiki/Resource_I ... _Info_Tags
http://en.wikipedia.org/wiki/Interchange_File_Format

In the second article:
"This is followed by a 32-bit unsigned integer (all integers in IFF files' structure are big-endian) specifying the size of the following data (the chunk content) in bytes."
In (32 bit) RIFF, the audio data is all in one "chunk". The size of that chunk is specified by a 32-bit signed integer. The largest 32 bit number is 4294967296 (decimal), so that is the maximum size of the RIFF data (audio) chunk.