[opendtv] Re: Closer

  • From: "John Shutt" <shuttj@xxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Tue, 4 Jan 2005 10:35:38 -0500

This brings up an interesting discussion we've been having here at our 
station for quite some time.  We decided to transcode PBS's 1080i HD feed 
down to 720p for transmission, because our experimentation showed fewer 
macroblocking artifacts on challenging scenes over the air using 720p at a 
lower bitrate (to make room for an SD subchannel.)

One of the arguments made against this was that since most displays (at the 
time) were native 1080i, those viewers would have to rely on the upconverter 
chip inside their sets or inside their ATSC STB to transcode the 720p back 
to 1080i for display.  Another argument was should we use the transcoder 
built into our Digital Vision Bitlink IRD, or should we purchase a high end 
transcoder to do the conversion.  An easy pocketbook decision said to go 
with the the Bitlink converter for the near term.

Which brings me to the nut of my question:  Have there been any studies on 
the relative quality of transcoder chips in various consumer devices such as 
Cable STBs, OTA STBs, and Consumer displays?  Is Sony's chip better than 
Panasonic's, or do they both purchase off the shelf solutions from a third 
party?  We know there are performance differences among ATSC demod chips, 
are there similar performance differences with transcoding chips?

How long before a high end video manufacturer comes out with a stand alone 
transcoder for true videophiles? (To be connected to the display with 
outrageously over-gauged Monster Cable so the video signal can 'breathe.')

Just staying curious,

John Shutt

----- Original Message ----- 
From: "Tom Barry" <trbarry@xxxxxxxxxxx>
> Craig Birkmaier wrote:
>>
>> When the box arrived Monday morning there was not much to watch.
>> Going through the set-up controls for the STB I had to choose 1080i
>> output, as this box ONLY supports 480i, 480P and 1080i outputs. I am
>> assuming that it converts 720P to 1080i after decoding, and that the
>> Samsung converts this back to 720P.
>>
>
> I think most of the cable HD boxes like my Motorola 6208 allow 720p
> output.  You would think the native output should always look better,
> though others also have reported that it is sometimes best to output
> 1080i from the cable box and let the TV handle it.  But this might have
> been for DVI inputs where passing 1080i digital could possibly allow
> more chroma resolution after the TV converted it. I don't recall for sure.

 
 
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