[QLab] Mixing bit rates

[jackarky]

Hey Gang,

I'm new to Qlab and just wondering if there are any issues mixing
audio bit rates in one cue list (or even within one cue)?
I recall in the past with other programs that mixing bit rates could
cause drop outs and other weirdness.
So far I haven't heard anything out of the ordinary, but just would
like confirmation on this.

Thanks,
Jack
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[Christopher Ashworth]

Hi Jack,

Correct, there are no problems with mixing bit rates in one cue list.

For codecs that support variable bit rate within the file, that is
also not a problem. (Note that with MP3s, which are the one codec
that off the top of my head I know for sure does this, there is
currently a bug where long MP3 files will be truncated.)

Best,
Chris

[jackarky]

Hey Chris,

CORRECTION: I meant to say bit DEPTH not bit rate.
Meaning, mixing 16 bit and 24 bit files in the same cue.

Good to know about mp3 as well though.

But mixing bit depths I'm assuming is okay as well correct?

Thanks,
Jack

[Christopher Ashworth]

Yup, variable bit depth is fine too. Everything gets converted to
CoreAudio's native format internally, which is 32 bit floating point.

Just a point of pedantic clarification: you can only have one file per
cue, where "cue" means a QLab cue. (Naturally, what "cue" means to a
stage manager could be multiple QLab cues.)

(mobile)

On Jul 25, 2009, at 1:35 PM, jackarky <jack...@earthlink.net> wrote:

> Hey Chris,
>
> CORRECTION: I meant to say bit DEPTH not bit rate.
> Meaning, mixing 16 bit and 24 bit files in the same cue.
>
> Good to know about mp3 as well though.
>
> But mixing bit depths I'm assuming is okay as well correct?
>
> Thanks,
> Jack
>

[Andy Dolph]

this discussion makes me wonder - what if you were to mix sample rates
in a qlist where files of multiple sample rates might be playing at
the same time.

Andy

On Sat, Jul 25, 2009 at 2:11 PM, Christopher Ashworth<ch...@figure53.com> wrote:
> Yup, variable bit depth is fine too.  Everything gets converted to
> CoreAudio's native format internally, which is 32 bit floating point.

[Christopher Ashworth]

Same as with bit depth. All files are converted on the fly (if
necessary) to match the sample rate of the audio device that is
receiving the file.

[Steven Devino]

Even so it would seem like best practice would be to pre-format everything to a single sample rate if possible.

Steve Devino

http://graniterockslive.com

603-867-6843

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[Christopher Ashworth]

If you're seeing high CPU loads, perhaps. Otherwise I'm not sure
you're buying much with the extra effort.

On Jul 27, 2009, at 10:19 AM, Steven Devino wrote:

> Even so it would seem like best practice would be to pre-format
> everything to a single sample rate if possible.
>
> On Jul 25, at Jul 25, 2009 2:33 PM, Christopher Ashworth wrote:
>
>> Same as with bit depth. All files are converted on the fly (if
>> necessary) to match the sample rate of the audio device that is
>> receiving the file.

________________________________________________________

[Jeremy Lee]

But you *are* sure of the quality of the SRC. I haven't compared
Quicktime/ CoreAudio SRC vs other tools, but there's likely a reason
that Peak's Quality 10 SRC algorithm takes FOREVER. Doing this in
real time is possibly sacrificing quality for expedience.

--
Jeremy Lee
Sound Designer, NYC - USA 829
http://www.jjlee.com

[Christopher Ashworth]

Fair point. I guess each person will have different standards for
different scenarios, and there will be different files involved. So
at the end of the day: use your ears, use the stuff between them, and
then act accordingly.

[jackarky]

Duly noted Chris! Personally, I think it's always good practice to
have all of your files conform to one standard and set your output
device to that standard. But on the off chance that you have an "oops"
or you're in a time crunch position where you just gotta throw the
file in as is, it's really nice to have the confidence that it's not
going to break your show.

Great discussion guys thanks!