[rollei_list] Re: OT - HDTV, was Turbines

On Jan 29, 2005, at 6:46 AM, Bernard wrote:

>>  Also, Sony did not have a video tape
>> recorder capable of the bandwidth necessary for the full
>> 1050 line system.

Was that 1035 lines?

> <snip>....the
>> business heads of the various broadcast/cable companies have
>> chosen to transmit poor quality video as HD. Much of what
>> you see is very highly compressed digitally and shows
>> typical motion artifacts and other artifacts. DirecTV in
>> particular, has chosen to compress its video to the point
>> where it looks like EP VHS to me. Since we originate HD at
>> Fox (720P) I have a pretty good idea of what the format is
>> capable of when done right. It is all too often done wrong
>> and that will eventually kill HD for cable or satellite use
>> if there isn't a great deal of better material made
>> available.

I wonder if it's fair to compare the extremely high compression rates 
of mpeg2 video to the lower rates used in digital recording?
For example, the HD being broadcast at 19 Mb/sec is around 80:1 
compression, compared to the uncompressed 1080i data rate of 1500 
Mb/sec.  But, mpeg2 is not a normal recording, since the large majority 
of the frames are not actually being recorded, but are derived from the 
few frames that are recorded (except in the case of something like 
Betacam SX, where every frame is actually an I frame).  And yet, mpeg2 
can look pretty darned good, except when the limits of its encoding are 
reached.

One way to look at it is, what are the artifacts of bad recordings in 
various formats.  So, the artifact of a bad analog recording might be 
different kinds of noise, or dropouts.  The artifacts of a bad digital 
recordings might be blocking, or complete loss of signal for a moment.  
The mpeg2 artifacts, such as you see in DirectTV or on DVDs, are often 
the simple failure of a compression scheme to represent the image it's 
trying to reproduce.

On the whole, I think all the compression schemes work remarkably 
well.... until one recompresses them, and *that's* where the real ugly 
pictures begin.

>
> I am always amazed, when I go to an edit suite, to see just how good 
> video can
> be. Even S-VHS can look a lot better than anything you can get from 
> cable or
> satellite at home. If I recall, Fox's preference was to stay with 
> standard def
> and work on getting a better quality signal into people's homes, but 
> they were
> in the minority.
> HDTV is a lot like the megapixel wars for digicams. People assume that 
> higher
> resolution means better quality, which is not necessarily the case. 
> Most
> consumers would assume that 1080i is better than 720p, for instance.

I rarely watch broadcast TV these days, and don't have cable or 
satellite, so I don't know what Fox is broadcasting.  But when the HD 
thing started, I recall they had elected to broadcast 480P.  Have they 
switched to 720P?


>
> Bernard
>

Ed Rudolph
San Francisco

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