[opendtv] Re: Olympics picture quality
- From: <tjharvey@xxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>, <opendtv@xxxxxxxxxxxxx>
- Date: Fri, 20 Aug 2004 12:04:43 -0400
Perhaps you could call what NBC is doing 'transcode'. However, the NBC
affiliates are decoding to uncompressed baseband from the 40Mb/s compression
and re-encoding to 18Mb/s for transmission to the consumer.
We are having to go through the decode/encode cycle at our broadcast station.
However technology is catching up and there are now 'economical' devices which
allow us to seamlessly splice and to insert logos on the MPEG-2 video without
decoding.
I would be curious to find out if NBC is decoding to baseband at New York. I
don't think they would be constricting the feed to the US. I would suspect that
everything incoming to New York for DTV network distribution must be decoded to
pass NBC's DTV network control.
Terry Harvey
>
> From: "John Willkie" <johnwillkie@xxxxxxxxxx>
> Date: 2004/08/20 Fri AM 12:12:44 EDT
> To: <opendtv@xxxxxxxxxxxxx>
> Subject: [opendtv] Re: Olympics picture quality
>
> From what I was told by the CE at an NBC o&o station in a brief telecon
> (we'll have a sit-down after the show is over) the only things coming out of
> New York is the news. His station's analog and HDTV feeds are COME DIRECTLY
> OUT OF ATHENS. New York is upstream from Athens in this configuration, not
> downstream.
>
> Here's how I understand it: MPEG-2 elementary streams are encoded in Athens,
> live, and they're decoded in the MPEG-2 section of digital TV sets in
> millions of homes.
>
> I haven't taken the time to check with the folks I talk to at the network,
> but this is the first time I've heard of a non-CBS network doing something
> like this: controlling stations from remote venues, not the TOC. Oh, yeah,
> TOC's control networks (legacy mode) and not stations.
>
> The biggest complaint one hears about this from CBS stations: "How come
> just the o&o's get this degree of control?" I've been told -- and not from
> official CBS folks handling this, who I've talked to more than a few times
> this year on "another" topic -- that all the stations could have this
> technology this year, after the o&o's work out the bugs.
>
> I can't say -- at this point -- that is exactly what NBC is doing. I will
> know within a week or two of the end of the games.
>
> Distribution and contribution are 45 Mb/sec. Transmission is 18 Mb/sec.
>
> And, of course, the stations do have to "decode" the 4:2:2 MPEG-2 signals to
> make them 4:2:0 for transmission. That's still required. But, you used the
> word "decode." Maybe I'm being pedantic/technical, but I tend to call that
> "transcoding." And, since it requires one to throw away bits, of course
> data is lost.
>
> When one takes a DS-3 feed down to baseband, unless I'm missing something,
> one should not assume that a single bit is lost.
>
> John Willkie
>
> -----Original Message-----
> From: opendtv-bounce@xxxxxxxxxxxxx
> [mailto:opendtv-bounce@xxxxxxxxxxxxx]On Behalf Of Terry Harvey
> Sent: Thursday, August 19, 2004 8:01 PM
> To: opendtv@xxxxxxxxxxxxx; opendtv@xxxxxxxxxxxxx
> Subject: [opendtv] Re: Olympics picture quality
>
>
> But are the NBC commercial inserts coming from Athens?
>
> It seems to me that the MPEG-2 video is going through three encode-decode
> cycles:
>
> Encode Athens, decode/encode New York, decode/encode affiliate, decode
> consumer.
>
> Even at two cycles at 45Mb/s coupled with an 18Mb/s cycle there will be
> sufficient loss to give MPEG blocking when there is sufficient motion in
> the picture (eg. swinging Olympic logo).
>
> I don't think NBC New York is passing the video through from Athens without
> decoding.
>
> Terry Harvey
>
>
>
> At 01:56 PM 8/19/2004 -0700, John Willkie wrote:
> >During the Olympics, NBC is being run out of Athens. Indeed, in the case
> of
> >o&o's, the local station is being switched out of Athens.
> >
> >All the nets use 45Mb/sec contribution feeds, save Fox (when their stream
> >switcher goes on line) which will be using 19.29 Mb/sec transmission feed
> to
> >affiliates.
> >
> >John Willkie
> >
> >-----Original Message-----
> >From: opendtv-bounce@xxxxxxxxxxxxx
> >[mailto:opendtv-bounce@xxxxxxxxxxxxx]On Behalf Of tjharvey@xxxxxxx
> >Sent: Thursday, August 19, 2004 10:58 AM
> >To: opendtv@xxxxxxxxxxxxx; opendtv@xxxxxxxxxxxxx
> >Subject: [opendtv] Re: Olympics picture quality
> >
> >
> >Doug,
> >
> >I made mention of this last Sunday. I understand the pictures are incoming
> >to NBC affiliates at DS3 rate of 45Mb/s, so the origination encoding from
> >New York, or wherever else it is originating from in the US is sending it
> >out at 45Mb/s. Affiliates decode and re-encode to 18Mb/s for transmission
> >and so there is a generational loss but it should not be all that bad.
> >
> >My question is how is NBC receiving it at New York? I suspect a third
> decode
> >is occurring before its US distribution to insert commercials. Or else is
> >the encode from Athens at a different rate from NBC's DS-3 distribution
> rate
> >which necessitates a third decode/ re-encode cycle?
> >
> >Anyhow, I see the artifacts too. In future the viewer is regularly going to
> >have to put up with this as the broadcast 'bean-counters' force limited
> >bandwidth. So just live with it and treat it as an interesting special
> >effect.
> >
> >Terry Harvey
> > >
> > > From: Doug McDonald <mcdonald@xxxxxxxxxxxx>
> > > Date: 2004/08/19 Thu PM 01:03:46 EDT
> > > To: opendtv@xxxxxxxxxxxxx
> > > Subject: [opendtv] Olympics picture quality
> > >
> > > Somebody here may well be able to answer my question
> > > on the picture quality of the HD Olympics.
> > >
> > > Sinclair only turned on their true HD here for the
> > > Olympics ... it was ready days earlier, but they absolutely
> > > refused to let us see some regular HD programming before the
> > > Olympics, so that's all I have seen.
> > >
> > > For static pictures, the quality (1080i) is certainly OK.
> > > There seems to be zero detail that my 720p TV can't handle:
> > > no change when I adjust the "sharpness" control, except for the
> > > local bug, and at CC It saw no more detail on 1080i sets, including
> > > the Sony XBR 950 set for "pro" mode, but it looks fine.
> > >
> > > However, when fast motion starts, such as the flying rings logo
> > > they use for replays, all Hell breaks loose: the logo itself
> > > breaks up into blocks, and is fuzzy to boot. I see no problem
> > > with flying logos on MNF (720p). When they show from-above
> > > distant shots of swimmers, the foam breaks up into total pixelated
> > > mud.
> > >
> > > When they show fast gymnastics, when they pan to follow a running
> > > gymnast, the background seems to move smoothly, so at least that
> > > part of the 50i->60i conversion is passable. BUT ... when the
> > > gymnasts have wailing arms or legs ... they actually disappear
> > > entirely! No, they don't get blurry ... there is no blur, just
> > > background behind where they should be. Well sometimes there is
> > > some faint trace or blurry stuff in front of the background,
> > > but not much.
> > >
> > > Clearly the broken up flying logos is a local encoder issue, but
> > > what about the foam breakup and the missing arms? Is this local,
> > > or due to the 50->60 problem? Has any of you people seen what the
> > > un-19.3'd network feed looks like?
> > >
> > > Overall I would say that both swimming and gymnastics has moments
> > > of simply unacceptably bad pictures.
> > >
> > > Mark Aitken: are you sure that the WICD people have got their
> > > encoder set right? Are you using the same brand of encoders
> > > at all your 1080i stations?
> > >
> > > Doug McDonald
> > >
> > >
> > >
> > >
> > >
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