RE: How to use Loudness Feature

[JohnB1]

Hi,

Is there a way to use the loudness feature in the Workflow?

My workflow looks like this, and don't know if it is right.

Folder ---> A/V Media ---> XDCAM-HD ---> Loudness ---> Folder

Someone, please guide me.

Thanks

[momocampo]

Hello John,

Ok, you have to understand that the loudness node just analyse the audio stream. You must use a conditional node after the analyse : f ex :
Folder>loudness(analyse)>conditional> loudness ok> delivery
> loudness no ok> ?(mail or delivery elsewhere)
Example for a stereo file: In your loudness analyse, populate a variable called (%loudanalyse% for ex) in "set level". Then, in conditional :"if %loudanalyse%" larger or equal to "[22.9,22.9]" (a parameter in each stream audio). At last, if loud is ok then delivery somewhere and if not, delivery elsewhere or do something else.
The loudness is -23 but I prefer to have a small margin.
I think it's not necessary to use av media even if you encode in xdcam.
Try and tell me if ok.



Benjamin

[admin]

If all you want is to make sure your XDCAM-HD files are within the loudness specs you only need this:

Folder ---> Loudness ---> XDCAM-HD ---> Folder

Otherwise, the use of conditionals in this regard is usefull for reports. But you can't test if something is larger than "[22.9,22.9]" because it's a string. You can test if the string is equal to another string but that is not what you want. So in order to test data in an array you should use the new $readarray() function: $readarray("%s_loudanalyse%", 1). This reads the first instance in the array. Use the "Populate"-node and store it into a new variable, f.ex. %f_loud% and use this new variable to test the analyzed loudness:
If $abs(%f_loud%+23) > 1 then the loudness if out of specs.

-steinar

[momocampo]

Thanks for these precisions Steinar, always useful I add it's quiet clever as process, thanks.

[JohnB1]

Hi,

How do I create the readarray() function and apply it to the workflow?

Thanks

[momocampo]

Hi John,

I think you have to use analyse loudness node first, then populate variable (%f_loud% to $readarray("%s_loudanalyse%", 1)) and use conditional node (If $abs(%f_loud%+23) larger than (>) 1 ).
It's like that I understand the Steinar's help. The thing I don't understand is if we use the $abs function, the result will be only positive, and a positive number is almost always > 1...
F ex : if a audio stream = -30 with loudness analyse (so in loudness specs):
$abs(-30+23) = $abs(-7) but with $abs function = 7. And 7>1 so out of loudness specs.
I 'm afraid I don't understand the process

[admin]

Functions in FFAStrans are just text strings, a bit like programming. They are valid in the "Populate variables" and "Conditional" nodes. So you just use them literally: $function(some data)

The point of using $abs() is that no matter how you twist and turn your data, it will come out as positive number. So f.ex.
$abs(-30+23)=7 (too low)
$abs(-16+23)=7 (too high)

That means you don't need to test for negative values, only positive as -30 and -16 are both out of specs. Does that make sense?

-steinar

[momocampo]

Hello Steinar,

I understand what you wrote but I think (maybe I'm wrong, I must check) the out loudness is only when the value is above -23 (so -22, -21,etc). If you have a -25 value, the loudness is ok because loudness is to avoid too high volume, not too low.
OK, we have to be the most closer to -23 but if you have a film with very little noise, it could be ok to pass loudness.
Cheers.

[JohnB1]

Hi,

Thanks will try and make this work.

[admin]

Benjamin, I think you are a bit wrong regarding loudness. The whole point is to make sure the percieved volume throughout at programme is consistant. The EBU-R128 standard says a programme should at overal be -23 LUFS ±0.5 dB but no more deviation than ±1 dB. So -30 and -16 are both out of specs.

-steinar