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Client wants Windows PCM, not Raw PCM - huh?

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Jean-Christophe Boulay
Client wants Windows PCM, not Raw PCM - huh?
on Sep 18, 2012 at 6:36:15 pm

Hi guys,

I've just received some specs that had me raising an eyebrow and would like a second (and third and fourth) opinion. It's for a batch of telephone system prompts. Most of the files are required in the usual mu-Law 16-bit/8kHz format, no problem there.

Then, for two files, they ask for "Windows PCM File (Not RAW PCM)". That's got me a bit puzzled. Either 1) I've missed something somewhere or 2) they want WAV files. Compounding the puzzlement is the requirement that the sample rate be 10025Hz, not the more usual 11025Hz (44.1kHz/4). I strongly suspect they want WAV at 11025Hz but I know telephone distribution systems like I know how to knit, which is to say not very much.

Opinions? Is there some special Windows-specific form of pulse code modulation at particularly non-standard sampling rates I've yet to learn of or are the specs perhaps... foggy? Getting to speak to the person who wrote these would imply wading through a few levels of clients and providers.

Thanks in advance,

JC Boulay
Technical Director
Audio Z
Montreal, Canada

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Michael Paul
Re: Client wants Windows PCM, not Raw PCM - huh?
on Sep 18, 2012 at 10:02:56 pm

My guess would be they're looking for a WAV file, like you suspect.

As for the sample rate, 10025Hz seems like a misprint and what they mean is 11025Hz. I don't think there is any wiggle-room in the WAV spec for 10025Hz.

If you can't get ahold of anyone who wrote the spec, I'd just go with 16-Bit/11025Hz WAV file.

Somewhere in the bowels of a government building, a disinterested functionary in the Dept. of Assembly Instructions and Recording Specifications is typing another Spec Sheet for your next job.

Or maybe I've just seen "Brazil" too many times

Michael Paul
Location Sound Corp

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Noah Kadner
Re: Client wants Windows PCM, not Raw PCM - huh?
on Sep 18, 2012 at 11:37:45 pm

Send them a test WAV with those specs- I suspect they'll be fine with it. Chances are the specs were cut/pasted from another spreadsheet someplace and something was lost in the translation. That said- that's a pretty low quality sampling rate- might want to advise them...


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Ty Ford
Re: Client wants Windows PCM, not Raw PCM - huh?
on Sep 19, 2012 at 2:41:37 am

Noah's right. 11k 8 bit files are hugely ugly for audio quality. Some phone systems are pretty gnarly though.


Ty Ford
Cow Audio Forum Leader

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Peter Groom
Re: Client wants Windows PCM, not Raw PCM - huh?
on Sep 19, 2012 at 8:26:30 am

I have seen the PCM wav option in a drop down in Cool edit pro waay back in ADDITIOn tot he Raw setting.
I think the sample rate is a error tho.


Post Production Dubbing Mixer

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David Watson
Re: Client wants Windows PCM, not Raw PCM - huh?
on Sep 19, 2012 at 5:54:00 pm

I agree with everyone else that the client wants a WAV file. I know in Audacity you can export to AIFF (Apple) PCM, but from what I can see there's no such thing as a RAW PCM. There are however options for signed, unsigned, U-Law, A-Law, Microsoft ADPCM, etc. encoding. Also, I took a 22050Hz/16-bit mp3 and resampled it to both 10025Hz and 11025Hz. Audacity reported the track after resampling as being at the sample rate I set (ie, 10025 or 11025). However any difference in sound quality was negligible and I'm not entirely sure if I perceived a difference due to "expecting" a difference. If you send the client a sample of WAV at 11025Hz, you may want to tell them that 10025Hz is an unusual sample rate and to double check if they want 10025Hz or the more common 11025Hz.

David H. Watson
dEhiN Entertainment

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