[QLab] External word clock and pitch problems, again...

[Nick Kourtides]

Hey list,

A month later, I've got a similar problem, with a different rig.  Here's the gist:

I'm in DC with a mine/theirs hybrid rig.  My computer and accessories, their sound cards mined from an ancient desktop running SFX 5.6.  It's a Mac G5 dual 2.0GHz with 3 Gigs of Ram, running QLab 2.3.3 (older versions have the same issue), with 2 Echo Layla 3G PCI cards installed.  The Laylas are locked to external word clock from a Yamaha DM1000.  The clock is running at 44.1KHz.

In December, I was in NY with an Intel Mac Mini, RME Fireface 800, DM1000, and everything clocked to an Apogee Big Ben.  Also QLab 2.3.3.  

In both cases, certain sound files will not play at the correct pitch.  In NY, with the clock at 48KHz, 48KHz wavs or aiffs would play fast.  In DC, I'm getting 44.1KHz files playing slow.  No kidding, I'm now running preshow music from a CD player.  

Is there something funny going on with how CoreAudio reacts to the sound card?  I thought that all media was resampled to match incoming sync.  Even so, I'm careful to keep the media at the same sample rate as the clock.  All files play just fine in Quicktime or iTunes.  The source of the media is either commercial music or recordings made in ProTools or Logic.  

baffled,

Nick

Nick Kourtides Sound Design

   

(215) 915 0159 cell

(215) 413 9501 home

nickko...@gmail.com

www.nickkourtides.com

 SN4149

[Christopher Ashworth]

On Jan 29, 2011, at 3:15 PM, Nick Kourtides wrote:
>
> Is there something funny going on with how CoreAudio reacts to the sound card?

Sounds possible. Do you get the same behavior out of the built-in output?

> I thought that all media was resampled to match incoming sync.

Yes, all media is converted on the fly to match the sample rate reported by the output device.

-C
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[Charles Coes]

Do all of the file headers look the same in soundhack?  Is any once source more likely to play at the wrong rate?  Commercial, Logic or PT?

Can you get one file to playback at the wrong speed simultaneously with a file playing at the right speed?

On the same system, using the internal sound output do you have the same issue?  Is it just the laylas?

Hoping he never runs into the issue...

Charles Coes
cco...@gmail.com 
www.charlescoes.com
"When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." - Buckminster Fuller

On Jan 29, 2011, at 3:15 PM, Nick Kourtides wrote:

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 SN4149

[Nick Kourtides]

Thanks Chris,

Built-in line output has no pitch problems.  Any thoughts? 

Nick

[Christopher Ashworth]

Things to check:

- Do only certain files play back at the wrong pitch? (And do they always do so?) If so, Charles Coes suggested checking the header information for those files in Soundhack, which seems like a good idea.

- If playing at the wrong pitch, is it all files or no files? (Can some files play back correctly while others do not?)

- If you simplify the system by turning off word clock, and just direct the audio to a single Layla that is not clocked, does it change the behavior?

On Feb 2, 2011, at 10:15 AM, Nick Kourtides wrote:

> Thanks Chris,
>
> Built-in line output has no pitch problems. Any thoughts?
>

> On Jan 29, 2011, at 4:10 PM, Christopher Ashworth wrote:
>
>>
>> On Jan 29, 2011, at 3:15 PM, Nick Kourtides wrote:
>>>
>>> Is there something funny going on with how CoreAudio reacts to the sound card?
>>
>> Sounds possible. Do you get the same behavior out of the built-in output?
>>
>>> I thought that all media was resampled to match incoming sync.
>>
>> Yes, all media is converted on the fly to match the sample rate reported by the output device.
>>