DirecTV Local Channel Acquisition and Encoding

Discussion in 'DIRECTV Programming' started by Bigg, Jan 20, 2018.

  1. Bigg

    Bigg Godfather

    568
    30
    Feb 26, 2010
    I can't find much on the topic, but is there a thread with good information about how DirecTV acquires and encodes local channels? Like how many of them are gathered via OTA versus fiber, is DirecTV encoding them directly from the broadcaster, or re-encoding the MPEG-2 feeds that are send OTA? Is all the national and regional content downlinked via C-band in El Segundo, and then uplinked to DBS?
     
  2. P Smith

    P Smith Mr. FixAnything

    26,146
    534
    Jul 25, 2002
    W.Mdtrn Sea
    too deep technically for the site - ask someone inside of DTV who in charge of OTA delivery
     
  3. Bigg

    Bigg Godfather

    568
    30
    Feb 26, 2010
    Where would you suggest asking that might know? If here, I don't know where would be better. I've seen a bit of discussion of it here and there on AVSForum, but never at length.
     
  4. studechip

    studechip Godfather

    1,824
    140
    Apr 16, 2012
    I remember seeing a list of what stations were gathered ota and which were by fiber. That was years ago, I don't know if it's still out there.
     
  5. studechip

    studechip Godfather

    1,824
    140
    Apr 16, 2012
  6. P Smith

    P Smith Mr. FixAnything

    26,146
    534
    Jul 25, 2002
    W.Mdtrn Sea
    that's was only "IMO"s, no real facts ...
     
  7. jamieh1

    jamieh1 Hall Of Fame

    1,573
    47
    May 1, 2003
  8. slice1900

    slice1900 Well-Known Member

    10,757
    1,569
    Feb 14, 2013
    Iowa
    Directv uses a combination of methods. There is one LRF per DMA as in the above list which are almost always on-site for at least one local station (check the addresses they list and you'll see) Some stations that aren't local to the LRF are delivered by fiber (which I'm pretty sure the station has to pay for) and the remainder are picked up OTA.

    The ones they get a direct on-site feed for and the ones delivered remotely via fiber are mostly getting the same MPEG2 feed that goes out for broadcast. Supposedly some channels get better quality feeds than what they broadcast by getting the MPEG2 encoded channel before it passes through the statmux to have its bandwidth trimmed to make room for all the subchannels in the 19.2 Mbps OTA broadcast signal. If they do get such 'raw feeds' it would allow for the possibility of getting better quality on Directv than what you can pick up OTA, otherwise you get the same quality or worse.

    Whichever method is used to get them, they then pass through an MPEG2 to MPEG4 transcoder, are sent via the LRF's link to one of six uplink sites (four regional uplink sites, in Arizona, Minnesota, New Hampshire and Washington, plus the two main broadcast centers in LA and Colorado) where they are uplinked to satellites at 99W and 103W, and finally broadcast to customers via the 99s and 103s spot beams you see on your receiver. Technically there are 12 uplink sites since each of the six has a backup, but that's not important for understanding the process.

    Unfortunately there is no way we can find out how a particular station is delivered to Directv, i.e. if they are picked up OTA, via fiber, etc. At least not from Directv; contacting the station's engineer is probably your only shot if you really want to know.
     
  9. trainman

    trainman Hall Of Fame

    1,715
    65
    Jan 9, 2008
    Sherman...
    If they're not at one of the local broadcast stations, LRFs will likely be found in a building that houses data centers and other colocation equipment. (That's what I found in several cities I checked -- aside from Los Angeles, where DirecTV uses their own facility, the LABC.)
     
  10. longrider

    longrider Well-Known Member

    4,181
    216
    Apr 21, 2007
    Elizabeth, CO
    That is exactly what the Denver LRF is, it is about 1/4 of a building near me and the rest is a data center. The LRF is maybe 2 miles from the diversity uplink for the CRBC (not that it matters for anything)
     
  11. James Long

    James Long Ready for Uplink! Staff Member Super Moderator

    50,327
    2,079
    Apr 17, 2003
    Michiana
    Interesting - in my market DIRECTV is in a building downtown, not near any of the towers (but line of site to all of them). The closest TV station is a couple of blocks away (the local PBS affiliate which purchased the CBS affiliate's former building).
    "AT&T Building, 307 S Main St, South Bend, IN 46601" Probably a coincidence.

    DISH's facility is a few blocks away and again not at any TV station's site. DISH backhauls on a private fiberoptics network operated by Echostar. Excess capacity on the network is available to TV stations and others who need to transfer video around the country, so I assume that some stations have fiber to the LRF just to be part of that network.
     
  12. P Smith

    P Smith Mr. FixAnything

    26,146
    534
    Jul 25, 2002
    W.Mdtrn Sea
    why everyone using the theoretical number ? there are PSIP, TS packet's headers, reserve for dynamic scenes, etc ... what max bandwidth noted for one main channel ? ~16 Mbps ... could be 18 max ?
     
  13. Bigg

    Bigg Godfather

    568
    30
    Feb 26, 2010
    Good information! So basically it's a hodge-podge and there is no way to know what's what.

    This is becoming more of an issue and a differentiating factor. Cable and OTA use the same stat mux, OTA one per 8VSB, and cable 2 per QAM, but with a lot of channels putting multiple HD channels or tons of SD subchannels into the stat mux before it's sent out, DirecTV would greatly benefit from either a direct HD-SDI feed, or a very high bitrate compressed feed that they could then use to make their own MPEG-4 mux for that market and spotbeam. With AT&T now owning DirecTV and operating a huge fiber network nationwide, I would think that more feeds would be going to high bitrate fiber? I see your point about being the same or worse if they're picking up OTA, in theory they could be slightly better if they have video processors that are out of the reach of consumers, but only marginally so, as they would be starting with a heavily degraded and compressed signal already in many cases.

    So then each of those 6 uplink centers re-uses the satellite bandwidth for uplink in a sort of reverse spot beam? With AT&T's nationwide fiber network, could the LRFs disappear, and each local station send a high bitrate MPEG-4 feed via fiber directly to their uplink site for encoding and uplink?

    That's too bad. It would be interesting to know, especially as ATSC 1.0 quality goes down the drain with channel sharing. ATSC 1.0 is capable of very high quality, but only with one HD and one or two SD channels in an 8VSB channel. Some are now up to 2HD/2SD in a single 8VSB, and the quality has taken a noticeable hit.
     
  14. slice1900

    slice1900 Well-Known Member

    10,757
    1,569
    Feb 14, 2013
    Iowa
    If they can get MPEG2 HD before it hits the stat mux, which would presumably be at 19.2 Mbps (minus the overhead for pedants like P Smith) I don't think there would be any noticeable improvement versus encoding raw HD-SDI to MPEG4. Directv is compressing MPEG4 HD channels down to an average of 6.5 Mbps so they are losing a lot of detail over what a full bit rate MPEG2 HD broadcast would have - I could easily tell the difference on the two channels I had that used to have no subchannels picking them up OTA versus what Directv broadcast.

    Around here my cable provider's quality exactly tracked what was being broadcast - because they're using MPEG2 anyway they simply pull all the video & audio streams from two local ATSC broadcasts and frame them in a single QAM channel. So just like OTA, cable used to be noticeably better than Directv on those two channels that didn't have subchannels. Directv was good but not as good, but now all sources are equally crappy since one of those channels has 3 SD subchannels and the other has 1 HD and 1 SD subchannel.

    While I agree that if they grabbed more channels before the statmux this really depends on what the station is willing to give them, and they aren't likely to spend money to change what they're doing now to improve quality.



    Yes exactly, from the four regional uplink centers it can use all 24 transponder frequencies even though the spot beams are only on 8 or 10 transponder frequencies depending on the satellite since they're "spot received". From the two national broadcast centers it can only use those 8 or 10 frequencies, because the other frequencies are used for uplinking CONUS transponders.



    I think the real solution will be with ATSC 3.0 - they'll have a (presumably) higher quality HEVC compressed main channel that Directv can transcode to MPEG4 at the maximum quality the MPEG4 bit rate they use will allow. Unfortunately whether the original source is 4K or HD the output will be the same 720p or 1080i on the Directv side since we'll never see 4K locals on Directv and they can't do 1080p because most of their hardware can't output 1080p60. The same is true with cable, except they will be able to deliver 4K locals if they come.
     
  15. jamieh1

    jamieh1 Hall Of Fame

    1,573
    47
    May 1, 2003
    My local stations have added quiet a few sub channels over the last year.

    My cbs now has 2 hd chs
    Cbs hd 1080i
    Cw hd 720p
    And 2 subs 480i


    Abc has
    Abc hd 720p
    3 sub channels 480i

    Fox has
    Fox hd 720p
    3 sub channels 480i

    Pbs has
    Pbs hd 1080i
    3 sub channels 480i

    Nbc hd 1080i
    2 sub channels 480i

    Ion hd 720p
    5 sub channels 480i

    And surprised pq is no bad.
     
  16. P Smith

    P Smith Mr. FixAnything

    26,146
    534
    Jul 25, 2002
    W.Mdtrn Sea
    I would guess its your TV good video processing doing that PQ
     
  17. Bigg

    Bigg Godfather

    568
    30
    Feb 26, 2010
    Would it necessarily be 19.2mbps? I thought that they produced content at much higher bitrates, and then fed all the high bitrates into the stat mux to make the final 19.2mbps mux?

    So 6.5mbps MPEG-4 is definitely a downgrade from 19.2mbps MPEG-2, I agree with you there, but the reality is that some broadcasters are down to an average bitrate of under 8mbps because they are channel sharing. If DirecTV could compress a 6.5mbps MPEG-4 (stat mux with other in-market channels?) satellite feed directly from HD-SDI or even a 19.2mbps MPEG-2 feed of the main HD channel, DirecTV's VQ would be significantly higher than OTA.

    Yeah, Comcast does the same around here. So I have to jump really in the weeds, two 8VSBs are a few hundred kbps more than one QAM, what happens to that bandwidth, or do all the OTA channels split the difference and run slightly under the bandwidth of an 8VSB to allow cable to easily re-pack their muxes?

    Yeah, it probably comes down to the money and the geography of where they are grabbing signals from. I'm sure most broadcasters would have no problem handing them off a higher quality feed if AT&T wanted to pay the dough for the fiber transport.

    Spot received. That's some pretty cool tech they developed for HD LiLs. Ah, I see, the CONUS uplinks are re-used as well. I wasn't even thinking about that, since I was thinking of CONUS downlinks. That ends up working out, since there just aren't as many markets around CA or CO as there are in the eastern half of the US.

    I don't think broadcasters will go to 4k, but that's another issue entirely. Since ATSC 1.0 has been so badly downgraded, hopefully ATSC 3.0 ends up being much better. In DirecTV's particular case, being under AT&T's ownership, wouldn't they just go to fiber everywhere, and pull uniformly high bitrate feeds for every channel back to the regional uplink centers? AT&T is the largest commercial fiber provider in the US, it seems like a piece of cake to do everything via IP fiber. If they do continue to use OTA, if a 720p channel went 4k, couldn't they then transcode the 4k signal to a really good looking 1080i60 channel, doubling the quality over the current 720p?

    The encoding technology has gotten way better. In 1999, when HD launched, it required the full 19.3mbps to get good quality, today they can get that same quality in about 12mbps. The problem is, many stations are now taking that technology to share channels with 2HD + 2SD or even up to 2HD + 4SD, the HD bitrates are now sinking under 8mbps.
     
  18. slice1900

    slice1900 Well-Known Member

    10,757
    1,569
    Feb 14, 2013
    Iowa
    I don't know if it is 19.2 Mbps or what, but there would be no real point in them producing at a higher bit rate than a single ATSC channel can carry - and no benefit to giving more than 19.2 Mbps (let alone HD-SDI) to Directv since it will be trimmed down to less quality than a 19.2 Mbps MPEG2 stream could carry anyway.

    There is is various overhead in the ATSC stream like PSIP that won't go in a QAM channel so I'm pretty sure if you carve out just the video streams you can make two of them fit in a single QAM without needing to do any shaping. I imagine if you google around you can find out exactly how much bandwidth the audio and video streams consume on a typical ATSC channel, and how much overhead there is on a typical QAM channel and see how well it'll fit.
     
  19. Bigg

    Bigg Godfather

    568
    30
    Feb 26, 2010
    The higher the quality the feed you give the encoder, the more efficient of an encode you get. The network master feeds are something insane, like several dozen mbps MPEG-4. Some C-band feeds distributing from the content providers to the MSOs are 15-20mbps MPEG-4. HD-SDI would preserve the original quality of the network master feed for network content before hitting D*'s encoder. I'm not sure how much of a difference it would make, but in theory, there is an advantage.

    Ah ok, that makes sense. Strip the overhead and it fits. Makes things easy for the cablecos to keep adding all the crappy subchannels!
     
  20. slice1900

    slice1900 Well-Known Member

    10,757
    1,569
    Feb 14, 2013
    Iowa
    True, but what I'm saying is I don't think it matters if you are stripping 19.2 Mbps MPEG2 down to 6.5 Mbps MPEG4. If you looked at it frame by frame you might be able to pick up a bit of difference here or there, but I seriously doubt anyone could tell the difference between starting with HD-SDI and 19.2 Mbps MPEG2 going to 6.5 Mbps MPEG4 in a live double blind side by side test.

    Even if a few people could, Directv isn't going to invest in HD-SDI to MPEG4 encoders when they already have working MPEG2 to MPEG4 transcoders in place, just for those handful of people. This is like item #3745 on their list of "things we can do to improve customer experience with Directv".
     

Share This Page

spam firewall