[opendtv] Re: Interlace Artifacts
- From: Ron Economos <k6mpg@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 12 Jan 2005 06:09:10 -0800
Comments in-line.
Tom McMahon wrote:
>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?
>
>
Agree that it's very much apples and oranges. I guess the reason
I responded was that most FOX 480p video bitstreams I've analyzed
(when they were doing 480p) were coded at around 10 Mbps. Quite
a bit higher than your typical 480i bitstream.
>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.
>
>
To use a Tom Barry phrase, I couldn't parse that sentence. Can you give
me another clue as to what you were getting at?
>Interlace has many dimensions. (Most of them bad.)
>
>
I get the feeling that folks on this list consider the interlace tools
in MPEG-2
(field DCT, field predictions, alternate scan) to be not adequate. In
another
post you said:
It is interesting to note that H.264/AVC has much improved
interlace tools that help mitigate the gas-guzzling problem,
but improved codec performance for the transmission channel
does nothing for the display problem.
As an old MPEG-2 guy, I haven't quite wrapped my head around
H.264 yet. Can you describe how the H.264 interlace tools have
improved over MPEG-2? I've also been told that the interlace
tools in VC-1 are a complete afterthought.
Ron
>-----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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