sd2 audio file conversion

[Sarah Newhouse]

Hi all, 

This isn't the best venue for this question, but would appreciate any help, even vague help.

I need to convert some sd2 audio files from circa 2001 into WAV/MP4 for researcher access. I have been able to find a few tools that will actually recognize the filetype and do the conversion, but the resulting WAV files are too fast/the audio is sped up. I don't have enough experience with digital audio specifically to know whether it's something in the conversion process that needs adjusting or something I can fix in the WAV in a tool like audacity.

Additional info: I've been able to get playable test files with SDTwoWAV (http://www.railjonrogut.com/sdTwoWav.htm), convertio (https://convertio.co/sd2-wav/), and filestar (https://filestar.com/). When possible, I've tried with both 48kHz and 44.1kHz sample rates, with the same result -- audio still too fast. The original filetype is old and proprietary enough that I'm unsure how to get information about the original sample rate (but I'm hoping someone knows a tool or trick!).

Thanks,

Sarah Newhouse

Digital Preservation Archivist

Science History Institute

[vma...@ucsd.edu]

Hi Sarah,

I had some sd2 files in a collection I just finished working on, do you have the resource forks for the original files? Those should have the info you need. (I didn't - had to guess sampling rates/other settings based on an included readme and hope for the best. I had good luck with sdTwoWAV.)

Anyone else have any ideas?

[Joe Carrano]

Hey Sarah,

I'm not familiar with sd2 or the conversion process. Maybe you've
tried this already but MediaInfo looks like it supports that container
type and could possibly give you the correct sample rate
https://mediaarea.net/en/MediaInfo/Support/Formats

Best of luck,
Joe

[Sarah Newhouse]

Just a bit of an update for anyone searching for similar issues in the future:

 I do not have the original resource forks. These files were copied onto CDs with no other information or readmes, alas. And so MediaInfo doesn't give me any helpful information -- just the filename and file size -- I assume because sd2s don't have much info in their headers.  

I tried changing the sample rate during conversion with sdTwoWav with no effect -- I don't know what the original sample rate was (or even if that's really the issue), but none of the standard sample rates produced a WAV file that sounded like normal speed. This is extremely hacky, but I had to get listenable MP3s to a researcher on a deadline, so I just manually tested a lot of different speed adjustments in Audacity until I found the one that sounded closest to "normal" (based on other available audio in the collection and just what sounded too fast/slow like breath intake and drawn out sounds in this spoken narration).

If anyone stumbles across this in the future and has suggestions, please reach out!

Sarah

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[co...@digitalsleuth.ca]

Hi Sarah, are you able to share one of the files to attempt recovery or perform analysis?

[Sarah Newhouse]

Further update, courtesy of Corey, and for anyone else working with sd2s:

It turns out Audacity can handle sd2 if you import as data, not as audio. So that solves every problem I was having without the hacky workaround. 

Thanks, everyone! (but especially Corey)