Re: [LAD] meterbridge 0.9.2 IEC-scale bug & fix

2012-09-26 Thread Chris Cannam 
[This went rather in one ear and out the other when you posted it (if
that's possible for email) but I did eventually realise I'd seen it.]

On 11 June 2012 18:47, Robin Gareus  wrote:
> Anyway, some of you who package or copied code from meterbridge may be
> interested in this as well.
> [...]
> //   def = (db + 60.0f) * 0.5f + 5.0f;  //  5.0  ..  10.0 // bug? v0.9.2
>  def = (db + 60.0f) * 0.5f + 2.5f;  //  2.5  ..   7.5 // fix!

You're quite right -- I just double-checked the standard and your fix
is the right one. I have cargo-culted this code into a couple of other
places myself without ever seeing this mistake, so I'll have to fix
those.

Thanks for spotting this.


Chris
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[LAD] LAO scheduled downtime

2012-09-26 Thread Robin Gareus 
Hi all,

Ico - director of linuxaudio.org - arranged to quadruple the disk-space
for our servers.

Amongst other things, this will allow us to host large
sample-collections (an endeavor Nils has started) as well as prepare for
videos from the upcoming Linux-Audio-Conference.

linuxaudio.org services will be offline for 5-10 mins later today
(around 45 min from now).

26/Sept - 16:00 UTC

thanks for your understanding.
robin
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Re: [LAD] meterbridge 0.9.2 IEC-scale bug & fix

2012-09-26 Thread Fons Adriaensen 
On Wed, Sep 26, 2012 at 12:08:00PM +0100, Chris Cannam wrote:

> On 11 June 2012 18:47, Robin Gareus  wrote:
> > Anyway, some of you who package or copied code from meterbridge may be
> > interested in this as well.
> > [...]
> > //   def = (db + 60.0f) * 0.5f + 5.0f;  //  5.0  ..  10.0 // bug? v0.9.2
> >  def = (db + 60.0f) * 0.5f + 2.5f;  //  2.5  ..   7.5 // fix!
> 
> You're quite right -- I just double-checked the standard and your fix
> is the right one. I have cargo-culted this code into a couple of other
> places myself without ever seeing this mistake, so I'll have to fix
> those.

There is more to fix.

The meterbridge website still claims that those meters 'almost' conform
to some standards while in fact they even don't come close. 

According to the standard, a VU measures the average of the absolute
value. For a steady input signal around 1 kHz, it must rise to 99% of
the real value in 300ms and overshoot it by 1 to 1.5% before falling
back to 100%. The one from meterbridge measures RMS and rises to the
final value in around 5.3ms, that is more than 50 times too fast (at
a sample rate of 48 kHz, and worse for higher sample rates). 

According to the standards, a PPM or IEC meter must have a controlled
rise time of 5 or 10ms (depending on the standard). The one from
meterbridge indicates peak sample values instead.

Ciao,

-- 
FA

A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)

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Re: [LAD] LAO scheduled downtime

2012-09-26 Thread Robin Gareus 
On 09/26/2012 05:12 PM, Robin Gareus wrote:
> Hi all,
> 
> Ico - director of linuxaudio.org - arranged to quadruple the disk-space
> for our servers.
> 
> Amongst other things, this will allow us to host large
> sample-collections (an endeavor Nils has started) as well as prepare for
> videos from the upcoming Linux-Audio-Conference.
> 
> linuxaudio.org services will be offline for 5-10 mins later today
> (around 45 min from now).
> 
> 26/Sept - 16:00 UTC
> 
> thanks for your understanding.
> robin

Back online. All systems go.

Cheers!
robin
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Re: [LAD] LAO scheduled downtime

2012-09-26 Thread Robin Gareus 
On 09/26/2012 05:12 PM, Robin Gareus wrote:
> Hi all,
> 
> Ico - director of linuxaudio.org - arranged to quadruple the disk-space
> for our servers.
> 
> Amongst other things, this will allow us to host large
> sample-collections (an endeavor Nils has started) as well as prepare for
> videos from the upcoming Linux-Audio-Conference.
> 
> linuxaudio.org services will be offline for 5-10 mins later today
> (around 45 min from now).
> 
> 26/Sept - 16:00 UTC
> 
> thanks for your understanding.
> robin

Back online. All systems go.

Cheers!
robin
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Re: [LAD] meterbridge 0.9.2 IEC-scale bug & fix

2012-09-26 Thread Gene Heskett 
On Wednesday 26 September 2012 12:58:35 Fons Adriaensen did opine:

> On Wed, Sep 26, 2012 at 12:08:00PM +0100, Chris Cannam wrote:
> > On 11 June 2012 18:47, Robin Gareus  wrote:
> > > Anyway, some of you who package or copied code from meterbridge may
> > > be interested in this as well.
> > > [...]
> > > //   def = (db + 60.0f) * 0.5f + 5.0f;  //  5.0  ..  10.0 // bug?
> > > v0.9.2
> > > 
> > >  def = (db + 60.0f) * 0.5f + 2.5f;  //  2.5  ..   7.5 // fix!
> > 
> > You're quite right -- I just double-checked the standard and your fix
> > is the right one. I have cargo-culted this code into a couple of other
> > places myself without ever seeing this mistake, so I'll have to fix
> > those.
> 
> There is more to fix.
> 
> The meterbridge website still claims that those meters 'almost' conform
> to some standards while in fact they even don't come close.
> 
> According to the standard, a VU measures the average of the absolute
> value. For a steady input signal around 1 kHz, it must rise to 99% of
> the real value in 300ms and overshoot it by 1 to 1.5% before falling
> back to 100%. The one from meterbridge measures RMS and rises to the
> final value in around 5.3ms, that is more than 50 times too fast (at
> a sample rate of 48 kHz, and worse for higher sample rates).
> 
> According to the standards, a PPM or IEC meter must have a controlled
> rise time of 5 or 10ms (depending on the standard). The one from
> meterbridge indicates peak sample values instead.
> 
> Ciao,

You are very correct, Fons.  However, as a BC engineer, I have observed 
severe clipping of the waveforms because they exceeded the headroom of the 
DA's, which in this case was _+28 dbm, while the true vu meter sitting on 
that same line was reading -3dbm peaks.  For average loudness readings the 
legal and pricey vu meter is fairly accurate, but it fails to detect the 
transients in todays music, or even in tv's spoken dialog during a soap, 
where the human ear as assaulted by the clipping cracklies the 70 year old 
analog std meter simply doesn't detect.  To that end, the best production 
audio boards are also equipt with the much faster LED setups that latch 
such a peak condition excursion for at least 100 milliseconds to make it 
obvious a peak has been exceeded.

To that end, the operators under my control have always been instructed to 
take it down a snudge until the overload LED at +16dbm only blinks at 5 
second or more intervals.  Listener fatigue can be very apparent in much of 
todays audio streams when the old 'vu' meter is peaking at _+4.

And it shows in the ratings books when those instructions are being 
ignored, folks might be fans of the program but something they only 'feel' 
makes them channel hop looking for a more pleasant experience.  When 1 
point in the ratings is as important as it is to a facilities cash flow, we 
look for every conceivable advantage.  Bad audio hurts.

Cheers, Gene
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
My web page:  is up!
Gary Hart:  living proof that you *can* screw your brains out.
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Re: [LAD] meterbridge 0.9.2 IEC-scale bug & fix

2012-09-26 Thread Fons Adriaensen 
On Wed, Sep 26, 2012 at 01:23:48PM -0400, Gene Heskett wrote:

> On Wednesday 26 September 2012 12:58:35 Fons Adriaensen did opine:
> 
> > There is more to fix.
> > 
> > The meterbridge website still claims that those meters 'almost' conform
> > to some standards while in fact they even don't come close.
> > 
> > According to the standard, a VU measures the average of the absolute
> > value. For a steady input signal around 1 kHz, it must rise to 99% of
> > the real value in 300ms and overshoot it by 1 to 1.5% before falling
> > back to 100%. The one from meterbridge measures RMS and rises to the
> > final value in around 5.3ms, that is more than 50 times too fast (at
> > a sample rate of 48 kHz, and worse for higher sample rates).
> > 
> > According to the standards, a PPM or IEC meter must have a controlled
> > rise time of 5 or 10ms (depending on the standard). The one from
> > meterbridge indicates peak sample values instead.
> > 
> > Ciao,
> 
> You are very correct, Fons.  However, as a BC engineer, I have observed 
> severe clipping of the waveforms because they exceeded the headroom of the 
> DA's, which in this case was _+28 dbm, while the true vu meter sitting on 
> that same line was reading -3dbm peaks.  For average loudness readings the 
> legal and pricey vu meter is fairly accurate, but it fails to detect the 
> transients in todays music, or even in tv's spoken dialog during a soap, 
> where the human ear as assaulted by the clipping cracklies the 70 year old 
> analog std meter simply doesn't detect.  To that end, the best production 
> audio boards are also equipt with the much faster LED setups that latch 
> such a peak condition excursion for at least 100 milliseconds to make it 
> obvious a peak has been exceeded.
> 
> To that end, the operators under my control have always been instructed to 
> take it down a snudge until the overload LED at +16dbm only blinks at 5 
> second or more intervals.  Listener fatigue can be very apparent in much of 
> todays audio streams when the old 'vu' meter is peaking at _+4.
> 
> And it shows in the ratings books when those instructions are being 
> ignored, folks might be fans of the program but something they only 'feel' 
> makes them channel hop looking for a more pleasant experience.  When 1 
> point in the ratings is as important as it is to a facilities cash flow, we 
> look for every conceivable advantage.  Bad audio hurts.

All very true. But that's no reason to claim that something that
just looks a bit like a VU meter but behaves *very* differently
actually is a VU meter. Same for the PPMs.

The code to this correctly has been available and GPL licensed for
4 or 5 years now (jmeters), so there's no excuse. 

Ciao,

-- 
FA

A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)

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Re: [LAD] zretune app added to libzita-resampler

2012-09-26 Thread Arnold Krille 
Hi,

On Tue, 25 Sep 2012 11:43:36 + Fons Adriaensen
 wrote:
> For example 
>   zretune --cent 50 input.wav output.wav
> will result in a file that sounds a quarter tone higher
> and is about 1.5 percent shorter.

Somehow I expected the above line to trigger an easter egg that takes
the input-music and does a cover-version as 50cents would do it;-)


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Re: [LAD] meterbridge 0.9.2 IEC-scale bug & fix

2012-09-26 Thread Chris Cannam 
On 26 September 2012 16:39, Fons Adriaensen  wrote:
> There is more to fix.
>
> The meterbridge website still claims that those meters 'almost' conform
> to some standards while in fact they even don't come close.

I'm not sure whether you're addressing me, but I have nothing to do
with meterbridge. My interest was limited to the IEC 268-18 extension
curve. Which I apparently should have done due diligence on.

Not sure whether Steve would be applying patches? If he isn't placed
to update it, it might be a better idea to tell people to use
something else (jmeters? with a link?) than to spend too much time on
specific issues with meterbridge. Especially if they've been described
before and if there is no way to get a fix through to anyone who picks
up the program from the obvious location or through a search.


Chris
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Re: [LAD] meterbridge 0.9.2 IEC-scale bug & fix

2012-09-26 Thread Gene Heskett 
On Wednesday 26 September 2012 23:48:57 Fons Adriaensen did opine:

[...]

> All very true. But that's no reason to claim that something that
> just looks a bit like a VU meter but behaves *very* differently
> actually is a VU meter. Same for the PPMs.
 
No argument here.  Most are better than nothing, but still lie like a rug 
under dynamic conditions.

> The code to this correctly has been available and GPL licensed for
> 4 or 5 years now (jmeters), so there's no excuse.

I wasn't aware of that bit of code, thanks Fons.

Now that I've been retired for over a decade, lots of that stuff goes right 
on by I'm sorry to say.  What does it use for its A/D converter?  Not all 
audio cards have sufficient depth to pull that off w/o the converter 
showing what a POC it is if the input level is off 3 to 6 db from ideal.  
My audigy2 value I would call just usable with its 24 bit range.

> Ciao,


Cheers, Gene
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
My web page:  is up!
Now I lay me down to sleep
I hear the sirens in the street
All my dreams are made of chrome
I have no way to get back home
-- Tom Waits
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