[mythtv-users] Obama Recommends Delay in Digital TV Switch

David Brodbeck gull at gull.us
Mon Jan 12 00:25:48 UTC 2009


Drew Tomlinson wrote:
> OK, I have to ask.  Now while I agree that sending "all the signal to 
> the rich neighborhoods" is silly, there certainly appears to be 
> occasions when commercials are much louder than the programming.

My guess is the peak level is no higher, but that they're compressing 
the dynamic range so that more of the audio is at peak loudness.  This 
is perceived as louder and "punchier" than uncompressed audio, because 
our idea of how loud something is is related to the average level more 
than the peak level.  Also, if you're watching a movie, movie 
soundtracks often have dialog and such at a fairly low level so that 
they have room to go louder for things like explosions.

Sometimes commercials also use Dolby Pro Logic encoding to send audio to 
the back channel speakers, if you have surround sound.

Now, in the case of locally-inserted commercials on cable TV systems, 
there may actually be a difference in peak level.  I've noticed that 
most cable TV systems do a really incompetent job equalizing the volume 
levels between channels and between locally-inserted content and network 
content.



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