[opendtv] Re: Time to give up on 1080i for football
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 8 Dec 2009 15:22:05 -0600
Tom Barry wrote:
> dan.grimes@xxxxxxxx wrote:
>> "If we are really to believe that 1080/60p takes up no more
>> channel capacity than 720/60p, then we are also claiming that
>> 720/60p takes up no more channel capacity than 480/60p, and
>> by logical extension, 1080/60p takes up no more channel
>> capacity than 480/60p." -Bert
>>
>> Your "If A=B and B=C then A=C" logic is infallible. But
>> your premise that anyone thinks A=B is absurd.
>
> I don't at all think A=B in that case.
>
> But, even if it did, that does not at all imply the second
> step, B=C. Imagine the case where for some reason there was no
> fixed overhead and yet NOTHING was ever encoded with an
> effective source resolution greater than that of 720p. This
> could happen because of poor cameras & telecines or simply
> because everything in the world was for some reason brick
> wall filtered to 720 rez, even if encoded at 1080p.
>
> In the above extreme case and without extra per block overhead
> it could (almost) be claimed 1080 = 720. But that would still
> say nothing about whether 720 = 480.
>
> So it was the second step of the logic I was disputing since
> B=C appeared as an intermediate conclusion, not a premise.
Whoa, Tom, I think you missed the point of my original reply. It was meant to
be a "reductio ad absurdum."
The comment has been made MORE than once, on this list, that 1080i is "less
efficient" than 720p. Fine.
The argument has also been made more than once that because progressive is
"more efficient," might as well code 1080/60p instead of 1080i. This is the
kind of vague semantics that get people in trouble.
THAT is what I was addressing.
Yes, 1080p is "more efficient" than 1080i by certain measures, but that's NOT
to say that 1080/60p takes up less channel capacity than 1080i for the same
quality images.
Proof:
Assume it is true that 1080/60p takes up equal or less channel capacity than
1080i, for same quality.
We already know that 720p takes up similar or less channel capacity than 1080i
for the same quality, right?
So if 1080/60p takes less capacity than 1080i, and
720/60p takes less or similar capacity than 1080i,
it MUST follow that 720p/60p takes up less or equal capacity than 1080/60p.
Which is absurd. (Modulo the bit about prefiltering to dumb down 1080p.)
Bert
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