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Posted by Jukka Aho on 12/05/06 21:49
Howard Brazee wrote:
>>>>> Okay, I'm shopping right now for HD tvs. I take it your set
>>>>> somehow senses the DVD anamorphic signal?
>>>>> If everything is configured correctly (no guarantee of
>>>>> that, of course), that's pretty standard.
>>>> How is that done in NTSC/ATSC land? You don't have SCART
>>>> connectors, so you can't use SCART pin 8 widescreen
>>>> signaling. You also can't use PALplus style line 23 WSS
>>>> signaling - at least not on line 23. So how does the set
>>>> know whether it is receiving full-screen 16:9 (16F16) or
>>>> full-screen 4:3 (12F12) signal from a DVD player?
>>> I get OTA digital HD to my Sharp Aquos, I don't want to pay for
>>> cable or sat. Shows that are widescreen come in widescreen, those
>>> that come in 4:3, come in regular. The tv changes everything on
>>> its own, as broadcasted.
>> That's understandable for OTA HDTV broadcasts. If the set has a
>> built-in ATSC (HDTV) tuner/decoder it can read the aspect ratio
>> flags straight off the digital stream.
>>
>> But what about playing back DVDs (which is what the original question
>> was about)? How does the DVD player tell the tv set "this signal is
>> full-screen 16:9" or "this signal is full-screen 4:3"?
> It wouldn't take much programming for a decoder to determine the
> aspect ratio.
DVD players and their MPEG-2 decoders can read the aspect ratio flags
straight off the MPEG stream on the disc. That was not the question. The
question was, as you can see from the above, how this information is
relayed to the tv set so that aspect ratio switching works
automatically. (Note: we're talking about full-frame 4:3 and full-frame
16:9 signals here. There are no black bars in the incoming signal that
the tv set could detect.)
--
znark
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