[BC] Balancing processing from analog to digital

[padrino]

Dana,

Theoretically speaking, you are correct. But, how many operators do this?
Not many from my vanatage point. How many VU meters did you replace
because board ops kept "pounding the needle into the red," and that drove
the console to the supply rails. 

In the real world, I just don't see it. As a matter of fact tey don't do
it with CDs. Discs today are mastered right up to 0dBfs, which really
means there's quite a few number of "dB's" of digital clipping going.

A well-designed peak limiter, and used properly, is non-obstrusive.

-Frank Foti

Broadcasters' Mailing List <broadcast at radiolists.net> writes:
>Frank,
>With 80 db of dynamic range, you don't need limiting at all. Or maybe at
>worst
>a protection limiter. 
>Run the level down 8-10 db, and you still have 70 db dynamic range.
>Eliminate
>pre-emphais, and 1 kHz's level increases 17 db over its level with analog
>FM.
>Just that will make level parity with analog pretty darn close.
>
>
>-D
> 
>------ Original Message ------
>Received: Thu, 21 Dec 2006 10:48:57 PM EST
>From: "padrino" <padrino at telos-systems.com>
>To: "Broadcasters' Mailing List" <broadcast at radiolists.net>Cc:
>"Broadcasters'
>Mailing List" <broadcast at radiolists.net>
>Subject: Re: [BC] Balancing processing from analog to digital
>
>
>Broadcasters' Mailing List <broadcast at radiolists.net> writes:
>>Agreed, Frank.
>>How much processing IS too much?
>>With FM, you do need processing for two technical reasons:
>>FCC peak modulation compliance and 75us pre-emphais (which makes the
>>former
>>even harder to do). The third reason that audio processing is used is for
>>the
>>subjective: "sound signature". This includes subsets of loudness,
>>brightness,
>>uniformity, etc., etc.
>>
>>
>>BUT...the main reason that peak limiting and or clipping is used is to
>>deal
>>with the first two.
>>
>>
>>These two are NON-EXISTANT with HD radio!!
>>
>>
>>That beng the case, why even bother woth limting and clipping?
>>They, more then anything else are the most destructive to audio. 
>>It seems to me that siing them is simply redundant.
>
>
>Dana,
>
>
>Actually, in HD Radio you do need a precision peak limiter. In this case a
>look-ahead version. Reason being is that, while you cannot overmodulate,
>you can bang into the headroom limit of 0dBfs. As most of us already know,
>digital clipping is nasty. Since HD Radio is operating at a 44.1kHz
>samling rate, any digital cliping of the system will cause aliasing of the
>audio, and couple that with a low (96kbps) codec and you *really* have
>problems.
>
>
>SO...You still need a precision peak limiter. Regarding your thread, the
>topic become, where or how much do you set that limiter. Look-ahead
>limiters do not offer the THD that clippers do, but dependent of their
>design, they can generate a LOT of IMD. Anyone who has ever dialed in more
>than 3dB of the limiter in the Harris Digit knows how bad that L-II
>limiter sounds. Nasty. But, al look-ahead designs are not as crude and
>rude as that. We offer an IMD masking network in ours and it does smooth
>things over considerably. (The prior was NOT meant as a commercial.)
>>
>>
>>
>>That said, the third reason (sound signature) is just as valid for HD as
>>analog. This by itself justifies processing for digital. I have no
>problem
>>with broadband and/or multi band AGC/compression. It's just the limiting
>>and
>>clipping that I have issues with.
>>
>OK, but you still need a precision peak limiter. See above.
>>
>>
>-Frank Foti
>>
>>
>> ------ Original Message ------
>>Received: Thu, 21 Dec 2006 01:09:50 PM EST
>>From: "padrino" <padrino at telos-systems.com>
>>To: broadcast at radiolists.net
>>Subject: [BC] Balancing processing from analog to digital
>>
>>
>>Dana,
>>
>>
>>I'm sensing that this thread is moving to the "processing vs no
>>processing" debate. Guess the question becomes, how much processing is
>too
>>much? Conventional FM will alwasys be too much, so to speak, due to
>>preemphasis. I'll bet that most folks do not realize that when they think
>>they're doing small amounts of processing on FM, they're still into "it"
>>more than they'd image, all because of the 17dB boost at 15kHz (75?s)
>here
>>in the USA, and 13dB (50?s) elsewhere. So, if you want to talk about
>>transients and punch, FM-Stereo basically offers an illusion to it. :)
>>
>>
>>What you desire, might play better on an HD-2 channel, at a higher
>>bitrate, like 48kbps, where that audio stream is not simulcasting the
>main
>>signal.
>>
>>
>>Sadly, while the discussion references the sound of CD audio, I'm sure
>>you've had a look at the dynamic range of those during the last 5+ years.
>>The processing done in mastering is almost on par with FM-Stereo.
>>
>>
>>An idea to ponder here, would be to employ META data with HD Radio. Then,
>>the consumer can choose the type of listening environment they desire.
>>
>>
>>-Frank Foti
>>
>>
>>Broadcasters' Mailing List <broadcast at radiolists.net> writes:
>> >Yes, cutting peak limiting back from perhaps 6-10 db to five will make
>> >things
>> >have more 'punch'. BUT...eliminating it all together will make it even
>> >punchier! Not to mention that conceptual coding algorithyms work best
>>with
>> >uncompressed audio as their source.
>> >
>> >
>> >Now, I understand how look ahead limiting works - and it's a good
>> >invention
>> >and innovation...BUT just like any good thing, it can be overused. 5 db
>> >of any
>> >limiting in a medium with a wide dymanic range like HD is about 4 db
>too
>> >much!
>> >
>> >
>> >The bottom line is this: I have heard all the HD stations in three
>major
>> >markets at length (NYC, Philadelphia and Boston). With a few standout
>> >exceptions, most HD audio sounds unimpressive. Why? BECAUSE of the
>> >processing!!  There's no "WOW!" factor!
>> >
>> >
>> >AND...In the case of the standout stations, EVERY ONE is a few db
>softer
>> >then
>> >their analog main channels. Secondaries too. I'm talking about audio
>>that
>> >sounds noticeably BETTER then the main analog channel. Who cares if I
>> >have to
>> >turn the radio up a bit? I'd do it anyway, because the music DRAWS ME
>IN
>> >when
>> >it sounds really good, instead of pushing me away, as crushed, clipped
>> >analog
>> >FM does.
>> >
>> >
>> >If we are going to claim 'CD like audio' for HD FM radio, we'd better
>> >deliver
>> >- and the crushed, limited MESS I hear on most stations just doesn't
>cut
>> >it!
>> >
>>
>>
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