[opendtv] Re: The old 720p/1080i argument again
- From: Eory Frank-p22212 <Frank.Eory@xxxxxxxxxxxxx>
- To: "'opendtv@xxxxxxxxxxxxx'" <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 3 Aug 2004 11:22:00 -0700
>From: "Cliff Benham" <cliff.benham@xxxxxxxxxxxx>
>To: <opendtv@xxxxxxxxxxxxx>
>Date: Tue, 3 Aug 2004 09:56:56 -0400
>I think you are wrong about where this is happening.=20
>
>The cable companies don't do the statmuxing of the
>digital SD signals they carry.
>
>The originating programmers do it.
>
>
>All the cable companies do is receive the multiplex with an IRD and
>feed it to a QAM modulator in the headend without any further
>processing.
True statement if you add the following caveat: "...without and further video
or audio processing." The cable TS is obviously not identical to a broadcast
TS, but those differences (SI vs. PSIP, changing PIDs, etc.) have no effect on
A/V quality.
>And for HD over cable, it's the same. The cable companies generally use
>an ATSC receiver that produces a DVB-ASI output which drives a QAM
>modulator
>directly without any further processing, so the bit rate of the HD
>signal
>is again set by the programmer.
Exactly as I have observed with comparisons of local HD stations on cable vs.
local HD broadcasts. The quality and bitrate differences between various local
HD channels originate at the source -- the broadcaster.
Cox cable here, like most MSOs, is promoting "HDTV" as a new service. They have
specific criteria they apply when evaluating addition of new HD channels to
that tier, such as % of prime time content that is broadcast in HD. For various
reasons, they don't want to advertise something as "HDTV" when it really is
not. For these reasons, they won't be carrying my local FOX affiliate's DTV
channel until the FOX network feed is 720p and the local broadcaster is passing
it along as 720p. Soon, I hope.
>As for decimated picture quality for both HD and SD, take a look at the
>two DBS
>systems. There you will see a far more serious lack of resolution and
>blocky mosaics.
This is one of the main reasons I stay with digital cable. Picture quality
sucks on satellite by comparison, especially for SD channels.
>What's the common thread here?
>
>Satellite transmission. The programmers try to squeeze as much as is
>possible into and out of
>each transponder.
Every MVPD has financial incentives to use his bandwidth efficiently. The
difference is that cable MSOs -- at least those with 750 MHz or higher systems
-- have some breathing room to add more services, like more HD channels,
without crushing picture quality in the process. Satellite transponders, on the
other hand, are squeezed pretty hard already.
-- Frank
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