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How exactly does one insert a logo for station or network branding without decoding the 720p MPEG stream back to HD-SDI then re-encoding it?
 

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It looks like they are going to send the signal out at less than 45mbs. Makes sense with this splicer system. Maybe Foxeng can explain this. He has been saying for some time that Newscorps has invested millions in ways to optimize hd transmission. My local affialiate has the specs and told be about this splicer system a few weeks ago. It sure makes sense to send the signal at 19mbs if it doesn't need to be re-encoded - also the engineer told me by doing it this way they can't really screw a lot up on thier end.



Excerpted from www.uemedia.net


Fox Network Installs Thomson HD Splicer Systems in Newsrooms


Those stations are currently broadcasting 480p widescreen content, but, in September, they're expected to begin 720p broadcasts. The 720p signal requires more bandwidth, which usually means higher transmission costs for the network and greater equipment costs for the stations. Fox is hoping to change that.


The splicer systems will allow the local stations to receive a more highly compressed HD signal and then insert, or "splice," local HD content, branding and data into the network stream without having to decompress it at the station. Removing that step ensures optimal signal quality because each decode and encode of an HD signal introduces the opportunity for artifacts and other quality problems.


For the network, the use of splicers means greater satellite bandwidth efficiencies and cost savings. HD network feeds are typically done via satellite at roughly 45 Mbps. And, if the Fox network requires multiple outbound signals--for example, during NFL telecasts--that 45 Mbps per feed becomes not only a cost issue but an issue of available satellite capacity. By using splicers at the stations, the network can compress the satellite feeds at rates below 45 Mbps and not compromise the quality of the signal.

http://www.uemedia.net/CPC/videograp...cle_6403.shtml
 

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I will try and explain this in layman's terms without getting too technical so some of my wording (for those in the know) may not be exactly Queen's English, but will hopefully get the point across.


OK, here is how it works.


FOX Net will "create" a 19.3 mps ATSC compliant 720p digital signal with DD5.1 already embedded, the same basic thing HDNet does. It will arrive at the stations over the current satellite receivers where it will come out into a special device that "insert" the FOX Net 720p signal into the stations 720p signal and on to the transmitter. You could say that FOX is mixing two 720p encoder streams together between the stations 720p encoder and the transmitter. This stream splicer uses a from of stream deconstruction that breaks the station's 720p stream down to a point that the 720p net stream is then mixed with in or out depending on what the station is trying to do, go to net, go to local. It isn't a hard cut because it if was, you would not have parts of the 720p stream in sync on reconstruction so different parts have to be deconstructed at different times and reconstructed in the proper order to be sure everything is synced up. Since this device can do all this, it would appear (I haven't seen it yet, the devices are not being delivered until March) that stations can "insert" their own branding (bugs, ID's, crawls, etc) within the 720p stream even if net is not on line.


The advantage to this system is it doesn't take a whole HD build out to pass network HD, just a 720p stream to the transmitter. In theory, a station really doesn't need a 720p encoder for this to work. A station could have just a 480i SD encoder, this splicer device and it could go between the 480i local and the network 720p. But the problem is, most receivers do not like the format switching on the fly like that and it could (would) cause receiver lockup at worst and very long periods of nothing between the switches while the receiver relocks in the least. In both cases, not good. Plus if a station doesn't have a digital link to their transmitter, this will not work. It isn't a panacea, but for those stations who only have an A/D converter and and upconverter into a digital link, it will cost them nothing to pass network HD/DD 5.1 and for those stations who have to do some money spending, it is CONSIDERABLE LY cheaper doing it this way than to have to build out a HD master control center with all the converters and such it would take. Cost savings to the stations ARE HUGE (cost to FOX is HUGE) thereby hoping that stations who otherwise would not have gone HD from net (due to money constraints), would now be able too. It also has the added advantage of uniform quality of the network signal from station to station, not this "every station has a different PQ" that everyone here bitches about. (see I told you the FOX people lurk here!) Another advantage is this technology was not available 2 years ago, but because of state of the art, it is now. The concept has been around for about 8 years (Sony developed it), but the hardware to make it all work at this advanced level (all this branding, etc) reliably (it takes a load of CPU power to deconstruct and reconstruct the stream in real time at 720p) is fairly new.


Now that is it in a nut shell. If you have additional questions, I will be happy to try and answer them.
 

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Foxeng -


I'm still not sure what deconstruct & reconstruct are. Do those involve decoding and recoding? Or are you saying it is possible with this equipment to insert a station logo without having to re-encode the signal?


- Tom
 

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Quote:
Originally posted by trbarry
Foxeng -


I'm still not sure what deconstruct & reconstruct are. Do those involve decoding and recoding? Or are you saying it is possible with this equipment to insert a station logo without having to re-encode the signal?


- Tom
No. The technical term is called "SPLICING" and you are really taking out and replacing. I guess the best way is to say splicing like you would with a genome, but I don't know if that is a better analogy (I don't know that much about gene splicing), or maybe interweaving like you do with different types of rope when you add rope or insert rope into another rope. Does that make any sense?


Anyway it isn't like how the other networks are doing with it where they have everything at 1.2 Gbs and cutting hard in and out to reroute signals. It is more like merging on an Interstate from an on ramp kinda thing where some traffic mergers in and then immmediately some other traffic leaves on another off ramp at the same interchange. Does that make any sense?
 

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One other thing you have to remember is that HD-SDI is uncompressed at 1.2 Gbs, ATSC compliant is 19.3 mps. You have a 10:1 compression ratio. It is my understanding that this device IS NOT decompressing and then recompressing. It is just opening up the stream, pulling out what it is not being used and then inserting what it wants all at 19.3 mps. That is why you splice it and not mix it in the traditional sense.
 

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Foxeng:


At some point in time, is it likely that our Fox station currently transmitting 1080i (mostly upconverted 4x3 SD programming) will switch to 720p for everything?


I think I read some comments to that effect when the Fox HD announcement first hit the forum, but the equipment specifics were not announced then AFAIK.


BTW, Foxeng, you are a great contributor to this forum in terms of helping those of us who are technically well beyond lay person but fall way short of TV broadcast engineering, particularly of the ATSC variety. I appreciate your willingness to share and your ability to explain the technical concepts in easy-to-understand (at least for me) language, analogies and examples.


Your contributions here help make the AVSForum the best source of what is happening and what is upcoming in the HDTV arena.


THANK YOU VERY MUCH!
 

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It is as clear as mud, and I like to think I am a little brighter than most!


Doesn't matter though, as long as Fox is willing to do this for us, I am pretty happy! Especially being able to get the DD 5.1 from network.
 

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foxeng - Although you say this in "layman's" terms most of it is still gibberish to me. But it is you engineers that are making more and more HD available due to innovations such as this. Though FOX is late to the game they may have gained an advantage in the long-run due to better, less expensive ways to deliver HD content.


My local FOX affiliate seems to have no agenda to start broadcast of a digital signal. They did not even respond to my inquiries. I am sure there are other FOX affiliates that are more tuned into customer relations.
 

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Quote:
Originally posted by foxeng
No. The technical term is called "SPLICING" and you are really taking out and replacing. I guess the best way is to say splicing like you would with a genome, but I don't know if that is a better analogy (I don't know that much about gene splicing), or maybe interweaving like you do with different types of rope when you add rope or insert rope into another rope. Does that make any sense?


Anyway it isn't like how the other networks are doing with it where they have everything at 1.2 Gbs and cutting hard in and out to reroute signals. It is more like merging on an Interstate from an on ramp kinda thing where some traffic mergers in and then immmediately some other traffic leaves on another off ramp at the same interchange. Does that make any sense?
That made a little bit more sense, though I'm still trying to figure it out.
 

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foxeng,


Thanks for the explanation. (And thanks for saying I had a "valid point" on the multicast thread.)


-Reagan
 

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Reviewing some of Terayon's other products, this device simply decodes the MPEG video, does whatever is necessary to the video -- adding branding or text scrolls -- then re-encodes it. The "big deal" is avoiding having to do any of this in a different domain outside of the box. It'll also handle switching between different sources -- local video of whatever source for locally-originated programming, ad insertion, etc. It does this within the local station's ATSC stream, preserving other subchannels that may be generated locally.
 

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I have a friend who is a Fox Eng. [7 Fox Stations] I asked him about this splicer thing and his answer was this.



_______________________________________


Hi Bobby,




A splicer is a MPEG switch. This will allow FOX to distribute HD at a bitrate (Quality) that is air-ready as opposed to contribution ready. The contribution signals require much more bandwidth on the satellite than the air-ready signals. To the viewer there will be no difference in quality. The network and broadcasters have gains behind the scenes that will ultimately lead toward more HD for the viewers.
 

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Discussion Starter · #15 ·
Thanks for the info foxeng.


Can't say I understand all of the terms, but I appreciate the explanation. It does sound like FOX has an innovative system for HD distribution.
 

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I think I understand this splicing stuff. Let's see if I can get this right using Winzip as an example. Let say your local station receives the compressed winzip file (720p signal) from Fox Net. Instead of the station unzipping (decompressing) the zipped file (720p signal), then adding other files (logo data ect.) then rezipping (recompress) then transmitting the compressed file (720p signal) they just drag a file (logo, data, ect.) into the zipped file (720p signal) and transmit it without needing the equipment to unzip and rezip (decompress & recompress).


foxeng,


Am I anywhere near the ballpark with my analogy?
 

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Quote:
Originally posted by Budget_HT
Foxeng:


At some point in time, is it likely that our Fox station currently transmitting 1080i (mostly upconverted 4x3 SD programming) will switch to 720p for everything?
It is possible. The station's encoder would need to be set to 720p and if the station has a 1080i plant, it would have to converted from 1080i to 720p. That isn't hard to do as long as the converter will down convert 1080 to 720. Some gear will, some will not.

Quote:
BTW, Foxeng, you are a great contributor to this forum in terms of helping those of us who are technically well beyond lay person but fall way short of TV broadcast engineering, particularly of the ATSC variety. I appreciate your willingness to share and your ability to explain the technical concepts in easy-to-understand (at least for me) language, analogies and examples.
Well it is the same thing I do at work for my viewers. Thanks for the nice comments.
 

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Quote:
Originally posted by Daryl L
Am I anywhere near the ballpark with my analogy?
It is close enough. As some others said, it is "switching" but it is switching by splicing in the compressed domain and not disconecting and reconnecting as is in the non compressed domain, which isn't as easy as it sounds.
 

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Quote:
Originally posted by Rakesh.S
let's hope fox can fix their bug by this fall..it's in the 4:3 frame and pretty annoying
FOX hasn't said how the picture area will be formated on the HD stream.
 
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