[linux-audio-user] sndfile-info and lots

[R Parker]

Hi,

--- philicorda <philicorda at ntlworld.com> wrote:

> Hope it all turned out right in the end!

I'm pretty confidant. As you may recall the order was
to achieve greater volume across a 13 song album. I
definitely accomplished that.

I installed Bitscope. Its numerical report for decibal
level of "Largest sample" combined with metering in
all the stages helped push the levels towards 0db.
I've always been nervous about hot levels but I think
we've got enough usable tools to confidantly do this
type of work.

After completing the first version, I referenced
against some "million dollar" masters and discovered
that my results are louder.

This was a useful discovery because it allowed me to
back the limiting off of several songs and minimize
the "munge" affect.

My overall review of mastering with Linux tools is
that we have what's needed to do acceptable work. All
of the tools have the expected bugs. No big deal. The
real upside to usability is that jack enables us to
configure routing scenarios that are perfect for this
type of work.

I used an Ardour session with 26 stereo tracks as the
source for JAMin. Thirteen of those tracks were for
existing masters and the other thirteen for the
unmastered control room mixes. At the hardware mixer,
I was able to use the mute button to switch between
the two sources and have the perfect A to B
comparisons.

When Ardour stabilizes and all its features become
usable, it and JAMin create an ideal setup. One of the
guys, Uwe, has written a LADSP module to automate the
scene changes in JAMin--I think it can be seen in
Rezound. Anyway, as things flush out I'm sure we'll
produce some documents describing how to setup an
ideal mastering environment.

Another studio owner friend stopped by and saw what I
was doing. He was impressed and said he's gonna buy an
x86 box and check out the linux stuff.

I've still got plenty to learn but with all the help
from everyone on this list I've been able to produce
an accepted product. Thanks much!

ron

> >There's been reference, on this list, to
> documentation
> >that explains file formats-- I don't recall the
> >document title or where to find it. Ultimately, I
> need
> >a resouce that explains things like; the number of
> >available samples for the different bit depths
> (16bit
> >range from -ABC to +XYZ, 24bit...), DC offset is,
> peak
> >amplitude is, RMS is, etc.
> >
> >I need to know if samples are syncronous with
> decibel
> >level, is maximum samples equal to 0db?
> >  
> >
> Yes. Though 0dbfs is perhaps a better way to put it.
> 
> Samples in 16bit= 2^16 Samples = -96dbfs range.
> Samples in 24bit= 2^24 Samples = -144dbfs range.
> Samples in 32bit float = I'm not sure if you count
> the Mantissa or not = 
> Shockingly massive dynamic range. (Almost exactly :)
> ).
> 
> >Of course another challange is tools like
> sndfile-info
> >assume that a file exists. This is not always the
> case
> >and in my situation it's almost never true. I
> return
> >JAMin output to an Ardour return bus and don't
> produce
> >a file until the return bus is exported. Printing a
> >track to the file system and then analyzing it is
> no
> >way to save time.
> >  
> >
> 
> I guess the only way some of those figures can be
> found is for the file 
> to be printed. Ie, you can only tell what the peak
> sample is if you have 
> compared it to every other sample in the file. To do
> it in real time, 
> you would have to have 'Peak Sample so far', 'RMS so
> far' etc, and reset 
> the figures manually when you started playback
> again. Not to say such a 
> facility would not be useful. It would be nice if
> Jamin had a statistics 
> page that showed you how many overs there had been,
> how many of them 
> were consecutive etc.
> 
> There is a new program called'Jackbitscope'
>
http://www.ecs.soton.ac.uk/~njl98r/code/ladspa/bitscope/
> this has displays for highest and lowest sample so
> far. (And lots of 
> other useful looking things I don't really
> understand. )
> 
> >Anyway, I appreciate all the responses to my past 
> >questions and am hopeful that someone can look at
> the
> >current mumbo jumbo and prescribe some effective
> >medications; coffee, sleep, black bear
> gallbladders,
> >urls to useful documents, etc.
> >  
> >
> Ground lion's teeth are effective in 90% of these
> cases in my 
> experience. If not.....
> 
> "0dbfs+ levels in digital mastering"
>
http://www.studio-systems.com/audiofeatures/SepOct2002/Audio%20Article/0DBFS+%20LEVELS%20IN%20DIGITAL%20MASTERING/78.htm
> It's a couple of years old but still interesting, in
> that it covers what 
> can happen when very hot digital levels hit the
> analog world.
> 
> Also, the rec.audio.pro faq is chock full of useful
> stuff...
> http://www.faqs.org/faqs/AudioFAQ/pro-audio-faq/
> 



	
		
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