Subject: Re: [linux-audio-user] sndfile-info and lots of questions
From: Mark Knecht (mknecht_AT_controlnet.com)
Date: Fri Apr 16 2004 - 21:01:52 EEST
R Parker wrote:
>
> I need to know if samples are syncronous with decibel
> level, is maximum samples equal to 0db?
Probably not. It all depends on how your system is calibrated. We've had
these discussions in the Pro Tools camp. The most standard final answer
is that you need to record a reference signal on your own and then
figure it out from there.
<SNIP>
> Signal Max : 25922
>
> Is Signal Max a measurement of used samples?
I *think* this is what the maximum number is in the file. 16-bit audio
is 65536 values. I suspect, based on some comments Steve Harris made the
other day, that this goes from something like -32767 to 32768, but
that's a total guess. There's one-complement and twos-complement stuff I
don't understand anyway, so it's likely a wrong guess. This would tell
me that you are at 25922/32768 % of max volume. Would that be about
right? This is a total guess though.
>
> One of the problems I've confronted during mastering
> is JAMin, Ardour and hardware meters tell me that a
> track is peaking around -0.5db but the hardware mixer
> indicates overload. Of course metering balistics being
> what they are this is understandable. The mixer
> documentation doesn't tell me at what level the
> overloads are set to go off at and I haven't found a
> configuration interface.
What sort of interface are you using between the PC and the mixer?
Analog? s/pdif? ADAT?
>
> With this metering and overload discrepancy I'd like
> to read a sndfile-info report that tells me; of the
> available samples, this file uses a minimum of X and
> maximum of X.
Again, I think that you should record some known values and then go from
there. One of the very first things I asked Paul to implement when I
first joined up maybe 18 months ago, was markers on the Ardour faders
that mean something. Pro Tools doesn't provide these. I think, how ever,
that their accuracy is probably dependent on the hardware you are using
(you're RME, right?) and may have never been verified for accuracy.
Don't know.
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