[opendtv] Re: Interlace Artifacts
- From: "David Workman (WINDOWS MEDIA)" <dworkman@xxxxxxxxxxxxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Wed, 12 Jan 2005 09:35:46 -0800
The decoders in the Media Player are backwards compatible with all
downlevel bitstreams. The 4:1:1 decoder is not part of VC1, but as far
as I know this format has never been deployed outside of the PC
environment.
>>I've also been told that the interlace tools in VC-1 are a=20
>>complete afterthought.
No, the main motivation for developing VC-1 was to properly support
interlace. The progressive encoding has some incremental improvements
over Main Profile, but all the big changes are in the interlace
encoding.
David Workman
QA Manager
Core Media Processing Technology
Microsoft Corporation
-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx]
On Behalf Of Tom McMahon
Sent: Wednesday, January 12, 2005 9:07 AM
To: opendtv@xxxxxxxxxxxxx
Subject: [opendtv] Re: Interlace Artifacts
So those encoders and bitstreams cause decoders to blow up?=20
-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx]
On Behalf Of David Workman (WINDOWS MEDIA)
Sent: Wednesday, January 12, 2005 8:57 AM
To: opendtv@xxxxxxxxxxxxx
Subject: [opendtv] Re: Interlace Artifacts
>>I read somewhere once on the MSFT site that they encode in=3D20
>>4:1:1 when you say you want to keep interlace. Dunno if=3D20 that is =
>>still true.
No. The original interlace mode encoding of Windows Media 9 "Main
Profile" was 4:1:1 but this has been superseded by the interlace
mode in "Advanced Profile", which is 4:2:0. The 4:1:1 mode is not
supported any longer.
David Workman
QA Manager
Core Media Processing Technology
Microsoft Corporation
-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx]
On Behalf Of Tom Barry
Sent: Wednesday, January 12, 2005 6:23 AM
To: opendtv@xxxxxxxxxxxxx
Subject: [opendtv] Re: Interlace Artifacts
Ron Economos wrote:
>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.
I read somewhere once on the MSFT site that they encode in 4:1:1 =
when=3D20
you say you want to keep interlace. Dunno if that is
still true.
- Tom
> Comments in-line.
>=3D20
> Tom McMahon wrote:
>=3D20
>=3D20
>>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?
>>=3D20
>>
>=3D20
> Agree that it's very much apples and oranges. I guess the reason I=20
>responded was that most FOX 480p video bitstreams I've analyzed (when=20
>they were doing 480p) were coded at around 10 Mbps. Quite a bit higher
>than your typical 480i bitstream.
>=3D20
>=3D20
>>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.
>>=3D20
>>
>=3D20
> 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?
>=3D20
>=3D20
>>Interlace has many dimensions. (Most of them bad.) =3D20
>>
>=3D20
> 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.=20
>In=3D20 another post you said:
>=3D20
> It is interesting to note that H.264/AVC has much improved interlace=20
>tools that help mitigate the gas-guzzling problem, but improved codec=20
>performance for the transmission channel does nothing for the display=20
>problem.
>=3D20
> 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 =20
>improved over MPEG-2? I've also been told that the interlace tools in=20
>VC-1 are a complete afterthought.
>=3D20
> Ron
>=3D20
>=3D20
>>-----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:
>>=3D20
>>
>>
>>>480p@60 uses the same bitrate or less as 480i@30? That would be a
very=3D20
>>>magical MPEG-2 encoder.
>>>
>>>Ron
>>> =3D20
>>>
>>
>>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
>>=3D20
>>
>=3D20
>=3D20
> =3D20
> =3D20
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