[opendtv] Re: 625 video quality is good enough....
- From: "Alan Roberts" <roberts.mugswell@xxxxxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Mon, 18 Oct 2004 18:20:28 +0100
I should point out that NHK was the co-producer on both occasions, and they
made no comment on softness. I know that they claim to have a spectacularly
good 50/60 converter in Tokyo, although I've seen no footage through it.
Also, I should point out that part of the argument in Europe over
*transmission* formats, is that material shot in 1080/50i would be converted
to 720/50p for *transmission*. That strikes me as daft since much of the
1080 programme production in Europe is in 1080/25psf, so we'd be
downconverting to 720p ,then frame repeating it. Hardly an efficient use of
bitrate.
The EBU's latest statement (R112, IIRC) is that there will be no single
*transmission* standard in Europe. It expresses a laudable aim to go
progressive, but admits that 1080/50p isn't practical yet. The initial
position that 720p would be the unique standard has been dropped, and a
system is envisaged where individual broadcasters may *transmit* 720p or
1080/50i ad hoc, perhaps even programme by programme. To me, that seems the
best compromise until a means is found of sending 1080/50p. It avoids
unnecessary standards conversion, which has to be a good thing.
None of this refers to programme *production*, only to transmission. On
current evidence in Europe, I'd put at least 95% of production being at
1080/50i or 25psf, mostly because much more of the installed base of
production kit is 1080 than 720, Varicam is the exception.
My 2 pen'orth.
----- Original Message -----
From: "Craig Birkmaier" <craig@xxxxxxxxx>
To: <opendtv@xxxxxxxxxxxxx>
Sent: Monday, October 18, 2004 3:57 PM
Subject: [opendtv] Re: 625 video quality is good enough....
> At 11:43 AM -0700 10/17/04, Dale Kelly wrote:
> >You might recall a recent posting suggesting that HDTV might be of
> >little value in countries using the 625 line system since that
> >system's quality was likely good enough. My position was, that as
> >good as that image might be relative to other analog based
> >standards, it could not compete in quality with true HDTV video
> >displayed on a 720 or 1080 large screen display.
> >I'm revisiting this subject only because I saw a very graphic
> >illustration supporting my argument last evening when viewing the
> >BBC production of "Last Night at the Proms", on the Discovery HD
> >channel. This is an excellent program in every way but it was
> >produced in the 625 (580? DTV) 16X9 format* and compared to other
> >HDTV programming on the same network was noticeably softer,
> >particularly on the medium and long shots which are such an integral
> >part of that program. Clearly the viewers in Britain would have
> >noticed and wanted the difference.
> >
>
> There is an obvious explanation, one that has significant relevance,
> as the ITU considers whether it should approve 720P for international
> program exchange, and the inclusion of 720@50P into the international
> standards.
>
> I cannot reproduce the submission to the ITU directly, however I can
> paraphrase the key points that the advocates of 720P have made:
>
>
>
> - Progressive formats make compression work better (one company
> estimates a 10%to 30% increase in the required bit rate for MPEG 2
> compressed interlace video as opposed to progressive scan video),
> preserving bandwidth and providing the best quality to viewers.
>
> - Emerging display technologies are progressive friendly and are
> dominated by 1Mpixel types.
>
> - 1280x720 is friendly to modern post-production techniques, which
> often need to de-interlace source for processing, such as spatial
> scaling and rotational manipulations.
>
> - Conversion from 720p to any other format is simpler and provides
> better quality because there is no source de-interlacing involved.
> This is the key to why Dale saw a "soft" picture. In order to present
> the content here in the U.S. the original 1080@50i source (thanks to
> Alan Roberts for this very useful clarification) had to be standards
> converted from 50i to 60i for broadcast by Discovery Networks. This
> requires a de-interlacing step, then frame rate conversion, then
> re-interlacing.
>
> Welcome to the realities of standards conversion. It does not get
> better with HDTV, if we are trying to do frame rate conversions on
> interlaced source. We are trying to create information that was not
> sampled, using samples that have been compromised by interlaced
> acquisition. The net result is that to cover all of the artifacts of
> the standards conversion, we give up significant resolution.
>
> Contrast this with a 50P to 60P conversion or visa versa. We do not
> need to de-interlace the source, and we have excellent spatial detail
> available to do the frame rate conversions. The results are obvious
> on a progressive display.
>
> So bottom line, Dale was seeing the "kinder, gentler, softer" side of
1080i.
>
> It's time to get rid of interlace. PERIOD!
>
> There is NO GOOD reason for this archaic compression technique to be
> concatenated with digital compression. This is equally true for
> SDTV(525 or 625 line), as better results can be obtained with a high
> quality de-interlacing system, before the source is subjected to
> MPEG-2 compression. Expecting a cheap de-interlacing chip in a
> consumer display to do as good a job as a $75K to 100K deinterlacing
> system is ludicrous. On the other hand, it is dirt simple to convert
> progressive source for interlaced display using noting more than a
> convolution filter to remove the details that would cause offensive
> artifacts on an interlaced display.
>
> If we only put progressive source into the DTV channel, the use of
> interlaced acquisition would
> disappear quickly, in favor of progressive HD and EDTV acquisition.
>
> Regards
> Craig
>
>
> ----------------------------------------------------------------------
> You can UNSUBSCRIBE from the OpenDTV list in two ways:
>
> - Using the UNSUBSCRIBE command in your user configuration settings at
FreeLists.org
>
> - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
unsubscribe in the subject line.
>
>
----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:
- Using the UNSUBSCRIBE command in your user configuration settings at
FreeLists.org
- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
unsubscribe in the subject line.
Other related posts:
