[opendtv] Re: Get rid of Interlaced Media?
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 24 Jan 2007 08:26:11 -0500
At 9:27 AM -0800 1/23/07, dan.grimes@xxxxxxxx wrote:
I have been working on a project that requires transforming our
interlaced video into MPEG-2 files. I know I'm stating the obvious,
but compressed interlaced media looks much worse than progressive
pictures in the MPEG-2 format no matter what encoding program I use.
And de-interlacing the video makes it much worse. When all the
planning went into the ATSC formats, was the way the formats would
be compressed and the resulting quality ever considered?
Yes, we fought a PROLONGED war over the use of interlace, both within
the ACATS process and later in the ATSC.
The position of the computer industry and even some of the system
proponents that were being evaluated for the U.S. standard was that
there was no need for interlace in a system that uses digital
compression. I might add that there were similar battles in ISO/MPEG
about the inclusion of interlace in the MPEG-2 and H.264 standards.
The fundamental argument against allowing interlace in the ATSC
standard was that the proper place to de-interlace is at the source,
not in the receiver. A TV station could easily justify the cost of a
high quality de-interlacing system from Teranex, Snell & Wilcox et al
ahead of the MPEG-2 encoder; it is not possible to justify the use of
an ~$80K de-interlacing system in an ATSC receiver.
One of the major reasons for the protection of interlace was the huge
investment by Japan Inc. in the 1125/60 (interlaced) HDTV system. In
the end they agreed to increase the number of active lines in the
standard from 1035 to 1080, as long as interlace was included in the
ATSC standard.
Interlace provided the CE industry with a wonderful tool to retrench
all kinds of IP that was either expired, or about to expire. They
took over the MPEG-2 standards process in the early '90s, adding all
kinds of tools to handle interlace to the standard; there are a large
number of patents issued in the early '90s that are referenced in the
MPEG-2 standard. When H.264 was created in ISO/MPEG the same suspects
did it again, entrenching the tools to handle interlace in the
standard.
In 1995 when SDTV formats were added to the ATSC standard we once
again fought to keep interlace out...
And once again we lost.
Regards
Craig
P.S. the other major reason that broadcasters fought so hard to keep
interlace was that it placed a significant barrier in the way of a
rapidly growing computer industry. Essentially, interlaced video
worked (still works) just fine on interlaced displays. But making it
look good on a progressive display added significant cost and the
results are NEVER perfect.
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