[mythtv-users] CALM Act in US

[David Brodbeck]

Brian Wood wrote:
>
> Commercials are produced using many forms of audio processing, usually 
> resulting in the audio being more "dense" (for want of a better term). This 
> processing makes it even harder to equate "level" with "volume" 
> or "loudness", especially when compared to the wide variety and quality of 
> program sources, which may or may not have processing of differing types 
> applied to the audio.
>   
I've noticed that another popular trick in commercials these days is to 
send a lot of audio to the back channels on Dolby Pro Logic systems, 
which effectively increases the loudness at the same volume level 
compared to a program that is mainly using the front and center channels.
> Much research was done in the 70s by the Orban Company, they made something 
> called an "Optimod", initially for AM radio, then FM and finally TV. Back 
> then the idea was to be the loudest station on the AM dial of course.
>   
Is this basically like the 'speech compressors' that SSB communications 
radios sometimes use to increase the average power level?
> AM Radio actually has an FCC-mandated spec of no more than 100% downward 
> modulation, now there's a great law: you're not allowed to reduce the power 
> below zero.
Well, sure, then they'd be stealing power from everyone else. ;) ;)

I used to live pretty near a big AM station in a rural area, and you 
could tell they ran their modulation level as high as they possibly 
could get away with.  You could hear brief bits of 'buckshot' splatter 
all up and down the dial on modulation peaks.