[BC] IBOC AM Quality

[Craig Bowman]

Frank,

I do not think anyone would argue that having good clean source material 
is the key to making low bitrate codecs sound tolerable (in the short 
term).  In this day and age most agencies, other stations, etc 
distribute spots in MP3 format.  Should you be discriminating enough to 
use uncompressed music, your codec falls apart during spot breaks not to 
mention talks stations have MP3 audio encoded programming via Starguide, 
etc.  I hear it now in analog and it can only be exacerbated by 
cascading data reduction algorithms.  In todays undereducated society 
(and I mean at radio stations) converting to .WAV files is the fix.  
Does DRM have the same low bitrate codecs?


Craig Bowman
Durand, MI


padrino wrote:
> Broadcasters' Mailing List <broadcast at radiolists.net> writes:
>   
>>> All of that being said, however, if you feed quality audio in, and 
>>> process carefully - by which I mean keeping the sound open, not 
>>> dense, and being careful about how you handle the high bands - AM 
>>> IBOC can sound quite nice.
>>>       
>> You have to have a continual supply of very good weed to believe the 
>> same grunge processing won't be used on the digital signals. It has 
>> to be. Otherwise the constant mode switching in cars will drive the 
>> listener nuts. Bad processing habits are very hard to break. The 
>> minute the General Manager hears his signal softer than the 
>> competition the order will go out to make it loud.
>>     
>
> No amounts of 'whacky-tobacky' needed. :)
>
> Processing for lower bitrates requires that the audio processing is NOT
> what we've come to know. Research has shown that low bitrate codecs DO NOT
> like clipping...NOR...limiting that contains high levels of
> intermodulation distortion (IMD). Most dynamic peak limiters exhibit high
> IMD and this causes added 'artifacting' in the coder. Just spent a good
> year working on this, and the proof is in the processing algorithms.
>
> Processing for HD does allow level normalization that eliminates
> discrepancies when the receiver switches back-n-forth.
>
> -Frank Foti
>
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