[opendtv] Re: Interlace Artifacts
- From: "Tom McMahon" <TLM@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Wed, 12 Jan 2005 00:06:53 -0800
This discussion treads on the usual apples and oranges problem. How do you
comnpare these things when the parameters associated
with the acquisition devices, the encoders, the storage media, the transmission
media, the decoders and the display devices are all
different?
Different MPEG-2 encoders may employ vastly different strategies depending on
what they're told to do and what they're fed.
A key concept in this is whether or not the original image was captured
coherently as single sample point. In other words, whether
or not it was "sampled" as a two dimensional array of image values or whether
it was scanned out as a sequence of intensity values.
Interlace has many dimensions. (Most of them bad.)
-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] On
Behalf Of Craig Birkmaier
Sent: Tuesday, January 11, 2005 7:51 PM
To: opendtv@xxxxxxxxxxxxx
Subject: [opendtv] Re: Interlace Artifacts
At 3:12 PM -0800 1/11/05, Ron Economos wrote:
>480p@60 uses the same bitrate or less as 480i@30? That would be a very
>magical MPEG-2 encoder.
>
>Ron
I can point you to many tests done in the '90s that proved this exactly. But
there is one caveat. Most of the tests used source with
equal information content then measured the SNR at the output of the decoder.
Thus, comparing an SDTV source with the same source
deinterlaced and coded as 480P the 480P signal would have a higher SNR than
the 480i encoding.
As a 480P signal can carry more information, it is possible that you may need
more bits to encode the source with the same SNR as
the information content increases. I beleive that NHK was covering live sports
in Japan with native 480P cameras with an emission
encoded bitrate of about 8 Mbps. This compares with about 6-8 Mbps for 480i
source, but the 480P was of significantly higher
quality.
Regards
Craig
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