Multicasting is a bad word around here, and even if you don't know what it means, we'd bet that you've seen it before. You know, your kicking back watching your favorite team and just when the action really gets goin', your beautiful HD picture turns into big ugly blocks as all the players move towards the ball. At that point all the expensive equipment at the stadium and your entire investment in your HDTV is all for naught, as your local affiliate decided it'd rather provide a useless 24 hour weather channel than deliver you the big game, sans blocks. We've all seen it happen and the beauty of the situation is usually the cable co' or satellite provider gets the blame instead of good 'ol News Channel 8. If you're one of the lucky few who doesn't know what this is like, according to a survey of broadcasters there's a good chance that you will, as 55 percent of those broadcasters surveyed said it had plans to multicast. The same survey indicated that only 66 percent planned to upgrade its facility so it could actually generate some HD content -- rather than just pass on the network feed. Unfortunately no one surveys us because no one cares, and the only thing we can do in protest is to not watch the useless channel -- like we need another 24 hour weather channel.
posted Feb 23rd 2008 6:52PM
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As someone who works in the field of broadcast television engineering I can say from first-hand experience that broadcast groups and owners are working to try and find some form of revenue stream from their (relatively) new DTV transmitters and you can expect more of the same picture quality degradation forthcoming.
In fact, when broadcasters settle on a winning mobile technology from the Open Mobile Video Coalition even more bits (between 4Mb and 5Mb) will be torn away from the primary (sometimes HD) channel and any other channels muxed into the stream.
In addition, there are datacasting providers like Building-B.com that look to grab bits from broadcasters in an attempt to create an improved form of the now-dead USDTV service.
It would not surprise me in the least if you see 1080i get swapped for 720p to allow the broadcasters more headroom for these endeavors in the somewhat near future.
Right now the over-the-air DTV broadcast is usually more robust than the molested, bit-rate reduced version on cable or satellite. As these new broadcast services roll out six months to a year from now the reverse may be true as the station could provide a higher bit-rate version via fiber to the cable head-end while squashing (multiplexing) HD, SD, Mobile Video and Pay TV/Data to fit in the 19.39Mbit pipe out the digital transmitter.
Boo. You know, when I heard that some broadcasters were switching from mpeg2 to mpeg4, i first thought
"hey great! better quality at the same bitrate!"
but they were thinking
"hey great! more stations at lower bitrate!"
not sure which is better.... i suppose more stations is worth it, when we actually get them.
As for multicasting... is this OTA only? or do cable and dish do this?
I'd think it'd be beneficial if one station had a commercial, they'd give more bitrate to the other station.... boost whichever program isn't in commercial. But that'd never happen...
I don't know of any U.S. broadcaster using MPEG-4 (although I would love that!) since MPEG-2 is the defacto standard of the ATSC, 8-VSB system. Other countries (like in Europe) are starting to use MPEG-4/h.264 to achieve lower bitrates for their HD offering.
It is possible to send MPEG-4 packets through the U.S. 8-VSB system to 'special' receivers as a form of datacasting, but the standard digital TV in the U.S. would only pay attention to and decode the MPEG-2 packets described in the PSIP (metadata). The average digital TV would/will ignore MPEG-4 or IP data packets and throw them away.
In the future, if manufacturers build in the capability for MPEG-4 or h.264 decoding into the sets it is conceivable that broadcasters could upgrade their encoders and 'flip a switch' to be broadcasting in MPEG-4. However, it would make the present ATSC MPEG-2 receivers in people's homes go dark - sound familiar?
It seems that here in Canada the CRTC is against multicasting, which might turn out to be nice when the broadcasters actually decide to stop twiddling their thumbs and start producing the majority of their content in HD.
Although having multiple channels of PBS is nice. It would be nicer if they weren't boxy quite often.
Newschannel 8? Ben, you wouldn't happen to be in the Tampa Metro Area?
Yep, I do and so I can't ever enjoy Sunday Night football without blocks.
Heh, News Channel 8 caught my eye too :P
HD really does suck in Tampa, at least WTSP actually started recording the HD primetime feed on Sunday mornings. A few years ago, if a scheduled Sunday Night game ran long, any programs that came on afterwards would be in SD :|
"Multicasting is a bad word around here, and even if you don't know what it means, we'd bet that you've seen it before."
Apparently you yourself don't know what the word means. Multicasting is the process of sending one digital/analog signal to multiple locations. This is opposed to unicasting (which is basically what's going on with plain ol' internet) where you send a signal to ONE location or broadcasting where you're sending one signal indiscriminantly over a network to theoretically an unlimited number of locations.
The term you're looking to use in this situation is most likely "multiplexed broadcasting" which is the process of combining multiple signals into one data stream.
While you are technically correct, the connotation of the word multicasting in this reference is shorthand for "multiplexed broadcasting."
Here's another example where it's used.
http://www.current.org/dtv/dtv0208multicast.html
As Ben said, you're both right. Multicasting is shorthand for multiplexed broadcasting although the confusion is justifiable.
My local Fox affiliate does the CW on its DT-2 and My Network TV on its DT-3 and the Fox HD picture still looks fine. And, I'd love to have NBC Weather Plus or the AccuWeather Channel in this market.
In theory I like this practice. Right now, I have no dish and no cable (the latter not being available at my house, in fact) which means limited programming, but on the bright side there's so little good programming in cable-space, plus there's no bill for broadcast TV for me, so woohoo! So the weather channel the local NBC affiliate runs isn't so useless to me.
Now, in practice...well, where I live, there's a number of hills, metal buildings, etc. so I also have problems with ghosting, which the American DTV standard doesn't handle well. In addition, afaik it's MPEG2-only, which means you have a need for a LOT more data.
The local PBS affiliate has four different digital channels running. FOUR. Three in standard def, and the fourth in high-def. I have no idea if the high-def channel is 1080 or 720, but they're running at such a low bitrate that it looks like poo.
I understand it's nice to have a weather channel OTA, but here in Tampa we have 3! Channel 8, 10 and 28 all have them, and for the most part it is the same thing on all three channels.
Our digital PBS channel is split into three broadcasts (two 480i SD and one 1080i HD). Ironically, they are the better looking of all the digital OTA channels I get even though they are being split up like that. The 1080i portion still suffers from bad macroblocking whenever there is movement, but you don;t notice it as much because PBS is not exactly known for its action packed programming.
The local ABC and CBS channels only have 1 additional channel being tacked on (both local weather radar feeds) but they often look worse than the digital PBS channels.
None of the digital OTA channels are what I would show friends to impress them with a great HD picture.
lol
Fox is 720p, which requires less bandwidth than 1080i. IMHO, all Fox transmissions are overtly soft and I suspect they are broadcasting a soft image to get by with a reduced bitrate from the beginning, similar to the bit shaving DirecTV does on their MPEG2 channels. Basically, it's either get a soft image or get pixellation with any fast motion when dealing with reduced bitrates. Now that I have Blu-Ray I see that OTA broadcasts are, well, crappy, with the possible exception of ABC/CBS in my market (but even they have some pixellation sometimes, but typically when flashes happen in the screen and not just fast motion).
24-hour weather? The local public station here in Minneapolis, the only one that broadcasts 24 hours of, non-stretched, but sometimes up-scaled (Nature), HD programing multicasts 6, 6! freaking channels...intermittent blocking is the least of it, here we have constant motion blur and ghosting. It looks as if like I'm watching my plasma through an LCD set...
Unfortunately, this type of multi-channel "capability" is obviously what broadcasters feel is the major selling point of the whole digital scene...One of the major stations here, WCCO Channel 4, apparently feels the the whole HD aspect of it is so hyped and overblown that they just recently stated that their news broadcast won't go HD for 1-2 years--after the dig switch over! The bizarre thing is their promotional adds feature the slogan "think inside the box" with the news anchors standing inside large stylized boxes, totally lost on the irony that they broadcast between pillar bars...