Do cable operators re-compress channels

Discussion in 'TiVo Coffee House - TiVo Discussion' started by nrnoble, Nov 12, 2017.

  1. nrnoble

    nrnoble Active Member

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    Full question: Do cable operators (ie Comcast) re-compress some or all channels?

    Example 1: Taking a OTA HD channel and increase the the compression so that the video quality is lower than what is received OTA

    Example 2: When I watch a rerun of some TV show, such as "Friends", on a cable channel, the video quality is noticeably lower than the video quality when streamed from netflix, hulu, etc.

    Example 3: HBO and other pay channels all have high quality video than other channels, and local OTA channels have the lowest quality.

    I am trying to understand if these differences in video quality is based on decisions made by cable operators, or are they just "passing-through" the video quality they receive from the source.

    I am assuming that the my Bolt is writing the channel stream directly to the HDD without processing it in such a way that would lower the video quality.
     
  2. JoeKustra

    JoeKustra in the other Alabama TCF Club

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    I don't believe my cable feed compresses anything. There has been threads on MPEG-4 with 720p conversion (Comcast) causing poor quality. I would check your bit rate and see if it's really low. Also, the cable signal can't be better than the source. My CBS and NBC channels added two sub-channels a year ago and I could see the change. One hour of 1080i was about 8GB and then dropped to 6GB.

    Busted! Comcast Down-Converts native 1080i Channels to 720P!!!

    Examples:
    NBC SNL 11.40Mbps
    CBS Bull 13.33Mbps
    TNT Major Crimes 13.52Mbps

    None are near the best cable should perform, about 18Mbps. Don't even ask about ABC.
     
    Last edited: Nov 12, 2017
  3. BigJimOutlaw

    BigJimOutlaw Well-Known Member

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    Tivos copy the stream they receive with no additional compression.

    Virtually all cable providers "transmux" some or most of their channels. Many channels that are broadcast in the 15-18 mbps range from the provider are compressed to 12-ish so that the cableco can cram more channels into their limited bandwidth.

    As mentioned in the previous post, comcast is notoriously bit-starving channels and downgrading them to 720p in the hopes you won't notice. :rolleyes:
     
    Last edited: Nov 12, 2017
  4. Diana Collins

    Diana Collins Well-Known Member TCF Club

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    Virtually every operator processes virtually every channel they carry. HBO, for example, distributes to the operators in MPEG4, and most of them convert it to MPEG2, since they have that kind of stat-mux processors. Stat-mux (statistical multiplexing) is a process that dynamically compresses the channels assigned, balancing the amount of compression across several channels. For example, if a carrier can support 36 Megabits/sec, and has 4 HD channels assigned, each gets a nominal 9 Mbits, but one channel may get 12 at times, while the rest get 8. It adjusts based upon the volume of data in each raw feed.

    To know if your cable operator is causing poor OTA quality, you'd need to see a direct OTA feed. Some locals multiplex several channels into their broadcast carrier, which can reduce the quality of the main feed.
     
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  5. powrcow

    powrcow Active Member

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    I started a thread about low bitrates on Cox a while ago: Cox Bitrates

    Like others have said, OTA *shouldn't* be compressed but delivered same as OTA. Bit rate can be reduced if your OTA channel has sub-channels.

    Some cable operators severely reduce bit rates to the point where it takes away from the content. I was seeing shows on FX on Cox at 5.6 Mb/s for MPEG-2 encoding. Another user had FX at around 13 Mb/s.

    TiVos record the bit stream as received.

    So your cable company can't do anything about OTA but can do whatever they want for cable channels. Mine (Cox) is continually degrading the picture. It's now at the point where almost all streaming services look better. The bonus is that my TiVo now has more storage capacity.
     
  6. kbmb

    kbmb Well-Known Member

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    Those are similar to my bitrates on Comcast in NH since the move to 720p (locals still at 1080i). Here are some examples I posted before:

    ABC 13.84 Mbps
    CBS 14.20 Mbps
    FOX 11.89 Mbps
    NBC 15.46 Mbps
    FXX 5.83 Mbps
    NBCSN 4.05 Mbps
    PBS 6.28 Mbps

    AMC before: 7.93 Mbps
    AMC after: 3.66 Mbps

    Just awful what Comcast is doing to cable channels here. 3-4 Mbps look like garbage on our 1080p set and are embarrassing on our 4K TV.
     
  7. aaronwt

    aaronwt UHD Addict

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    Comcast in my area further compresses the local broadcast stations> but FiOS doesn't. My Fios recordings are the same size as my recordings from OTA. Which is nice that FiOS doesn't futher compress the local stations yet. Because FiOS is certainly doing it with many of the cable channels. The quality of many of the FiOS cable channels is nothing like it was ten years ago.
     
  8. JoeKustra

    JoeKustra in the other Alabama TCF Club

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    I feel for you. As for the broadcast networks, I always check Wiki and see how many sub-channels have been added. I don't watch a lot of ABC, but your number is quite nice. I mostly record CBS and NBC, so when the sub-channels were added I noticed it right away. Until 4k becomes more available, I'll stick with my 1080p TV. I'd need a new AVR anyhow. Maybe next year. If somebody came out with 1080p HDR10 I would jump on it.
     
  9. kbmb

    kbmb Well-Known Member

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    Only network we still watch on Comcast is CBS. All ABC and FOX shows we watch on Hulu OnDemand (non live version). Those are beautiful 1080p streams (only downside is the 2.0 stereo). Premium networks (HBO, Showtime) we stream through the apps to get 1080p. We had to put up with the last season of Halt and Catch Fire on AMC in that awful bitrate.
     
  10. nrnoble

    nrnoble Active Member

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    How are you determining the bit rate? Downloading to a computer and using some video utilities?
     
  11. kbmb

    kbmb Well-Known Member

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    Just connecting via KMTTG will show the bitrate of the recording.
     
  12. JoeKustra

    JoeKustra in the other Alabama TCF Club

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    If kmttg is too much, this works -> OLED - ROAMIO PLUS & Comcast "Picture Quality"

    Size is at the end of a program's Info data.
     
  13. dlfl

    dlfl Cranky old novice

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    As @Dan203 has said:
    in this post:
    Cord Cutting Surprise
    I would doubt a statement made earlier in this thread that cable operators could or would never recode a terrestrial (OTA) signal to a lower bitrate.
     
  14. NashGuy

    NashGuy Well-Known Member

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    I would assume that *every* multichannel pay TV provider (cable, satellite, telco, OTT) is recompressing at least some, if not all, channels all the time. Some providers use more drastic compression than others and, within any given provider, some channels tend to look better than others. Google Fiber TV may be an exception to this since it's IPTV running through a network with lots of bandwidth. I've read that they don't recompress anything, although I'm not sure if it's true.

    I haven't tried any of the OTT "vMPVDs" but I've read good things about the picture quality of DirecTV Now. One user posted that it looked better to him than DirecTV satellite. Netflix, of course, looks better than any cable or satellite source I've ever seen.
     
  15. JoeKustra

    JoeKustra in the other Alabama TCF Club

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    Mine doesn't. But that doesn't stop its content providers from doing it.
     
  16. Dan203

    Dan203 Super Moderator Staff Member TCF Club

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    We have a customer who picks up the main network feeds using one of those big dishes. They're like 35Mbps H.264 with Dolby-E audio. Almost BluRay quality. By the time the local affiliate send it to you,or your local cable operator, it's been converted several more times and has significantly less quality then the original.
     
  17. kbmb

    kbmb Well-Known Member

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    For me, even though Comcast kept the locals at 1080i and the higher bitrates.....they still can't touch even the Hulu 1080p display. Everything on Comcast looks soft on the locals.
     
  18. NashGuy

    NashGuy Well-Known Member

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    Who is your TV provider? And are you saying that this provider transmits channels via QAM to the STB in a mix of both native MPEG-2 and h.264 MPEG-4? Because OTA stations, of course, broadcast in the former and most if not all cable networks provide their feeds in the latter.
     
  19. JoeKustra

    JoeKustra in the other Alabama TCF Club

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    After reading the earlier post (18), and seeing the dish farm at my headend, I can understand that the received satellite feed will undergo some changes. My locals come via fiber and they have a lower bit rate than my basic cable networks. All my channels are MPEG-2 but I also get SD mirror channels. There are OTA stations in my feed, but my cable office, like my location, has little chance of receiving them.
     
  20. reneg

    reneg Well-Known Member

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    Not sure this is an apples to apples comparison, but this is what I am seeing in Houston on both OTA & Comcast in Mpbs as reported by kmttg:
    Code:
    Mbps    OTA     Comcast
    ABC     ~8       ~8
    CBS     ~13     ~13
    CW      ~12.8   ~12.8
    Fox     ~15     ~15
    NBC     ~13.4   ~13.4
    PBS      N/A    ~5-10
            
    USA             ~4.2
    TNT             ~4
    AMC             ~3.8
    FX              ~3.9
    FXX             ~3.9
    BBC             ~3.7
    
    I seem to recall that after the Comcast MP4 change, bitrates on locals were much lower, but it looks like the bitrates are on par for the locals that I receive.
     

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