[BC] I got my HD radio

[Robert Meuser]

I think someone conciously made sure the signals sounded identical. My 
comment was more my surprise they would leave that much clipping in the 
L/R domain rather than composite which would only address the analog 
channel.

R

Robert Orban wrote:

> At 04:17 AM 12/8/2005, you wrote:
>
>> From: Robert Meuser <robertm at broadcast.net>
>> Subject: [BC] I got my HD radio
>> To: Broadcast <broadcast at radiolists.net>,       Broadcast Radio 
>> Technical
>>         Forum <radio-tech at broadcast.net>
>> Message-ID: <4397B00D.5000700 at broadcast.net>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>> I just purchased a Boston Acoustics receptor. Look for more detailed
>> reports in other forums. Initial reaction - disappointment. By the time
>> I got home with my purchase it was too late to evaluate AM.  For FM WNYC
>> (PBS) and most of the Clear Channel stations where 'perfect' if you
>> considered blend. The bad part is that means the blend is so subtle that
>> there is no real discernible difference. WPLJ (ABC) also fits that
>> category and remains the loudess most obnoxious station in the market.
>> Their IBOC signal seems to proove that there is a lot of L R clipping
>> happening.
>
>
> If there is ANY L/R clipping appearing in the HD channel processing of 
> a station, then someone made a big mistake setting up the facility or 
> the processing. In Optimod HD processors, there are no clippers in the 
> HD channel so you couldn't purposely add L/R-domain clipping even if 
> you wanted to. L/R clipping is just about the worst thing you can do 
> to a low bit rate codec because the codec starts wasting bits trying 
> to encode the clipping distortion.
>
> The only peak limiting in an Optimod HD processing chain is the 
> look-ahead limiter right before the output, and the output waveform of 
> the look-ahead limiter looks nothing at all like the output of a 
> clipper. If you see clipping at the processor's output, this would 
> have to be caused by clipping in the source mastering process, 
> insufficient headroom in the program chain somewhere before the on-air 
> processing, and/or overdriving the processor's A/D converter if the 
> unprocessed signal is analog, which is rare in major markets these days.
>
> (BTW, I am awaiting delivery of my Boston Acoustics Receptor. I order 
> it from Crutchfield and expect it by the end of the week.)
>
> Bob Orban
>
>
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