TV channel bandwidth question?

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  • #51933
    mwdxer1
    Participant

    We have a new Weigel translator on the North Oregon Coast, K36LI-D. It runs 5 SD feeds (1-H&I, 2-Start TV, 3 Movies!, 4 Decades 5 METV+). I have been watching the channels for a few days and the SD pq is pretty good. better than some of the regular TV stations, where they have to add the SD channels to an HD channel. I have no idea how much bandwidth the 5 streams are using. If they were divided up equally, which they may be, any idea what the bandwidth would be on each stream? I was guessing 3-3.5 each. That would get out between 15-17.5. Thanks.

    #51934
    Andy Brown
    Participant

    There is not a unique answer to that question as there are numerous variables that can effect the number including but not limited to frame rate, encoding, actual resolution and compression. Your guess appears to be higher than much of the information out there that’s recent. It is also constantly changing. SD is a range of resolutions just like HD is.

    #51935
    nosignalallnoise
    Participant

    any idea what the bandwidth would be on each stream? I was guessing 3-3.5 each. That would get out between 15-17.5. Thanks.

    Bitrate, not bandwidth. 44100 Hz is bandwidth, 320 kilobits per second is bitrate (throughput).

    The bandwidth of a terrestrial or cable TV channel in the USA is always 6 MHz, be it NTSC or any of the digital transmission systems. No more, no less.

    There are various devices and computer peripherals on the market that can analyze a multiplex and show the bitrate of all the streams in it. In fact I think a few of the higher-end sets and set-top receivers can do it. Time to hit Amazon. Sorry, but this is something probably only you would be able to tell us since I don’t believe any of the rest of us are within observable range of K36LI; I definitely am not.

    #51937
    radiogeek
    Participant

    This reminds me of a quote some of my friends have shared;

    “The good thing about standards is how many there are”

    Ed

    #51938
    mwdxer1
    Participant

    Thanks for the replies. I figured anything would be a guess, and I did not take in the possibility of varying bit rates. I do know their pq is good. I also have no idea if a Portland station engineered the translator set up or, the engineers came from Weigel, maybe KFFV Seattle?

    #51942
    billmcf
    Participant

    You may be able to get this information from rabbitears.info. I just checked, and the new station is listed, but the data rates aren’t filled in yet.

    #51944
    Alfredo_T
    Participant

    In my recollection, somebody on this board stated that today, many DTV multiplexes dynamically assign the throughput allocated to each of the virtual channels. Thus, your answers would be ballpark figures, rather than exact numbers.

    #51949
    nosignalallnoise
    Participant

    Yes, most newer ATSC encoders are statmux-based. Basically the overall bitrate of each program stream (audio and video) is dynamically adjusted on-the-fly based on the activity of other MPEG-2 program streams in the same transport stream multiplex. (*a.k.a. “statmux” or “statistical multiplexing”) You can probably analyze a program stream over a period of say two hours and calculate an average bitrate figure. Otherwise it’s effectively a variable-bitrate scheme, like most commercial DVD-Video discs, so there is no fixed-bitrate figure to state.

    DVB-S and Direct-TV DSS have had that feature for a very long time.

    http://www.coolstf.com/mpeg/ — This page talks in great technical detail about this stuff. The page is almost 20 years old and is extremely DVB-S centric (ATSC was still early in its childhood then) but most of the same basic principles apply.

    #51983
    kleinmelody
    Participant

    I think television will disappear soon as YouTube appeared

    • This reply was modified 3 weeks, 3 days ago by kleinmelody.
    • This reply was modified 3 weeks, 3 days ago by kleinmelody.
    #51993
    Alfredo_T
    Participant

    YouTube has been in existence for about 15 years, yet TV is still with us.

    #51998
    mwdxer1
    Participant

    I think OTA TV will be around for a long time. New stations & translators (like here) are come on often. Weigel Broadcasting believes in OTA. I am glad they do too!

    #52000
    radiogeek
    Participant

    This video reminds me of this thread, with it’s predictions of OTA becoming obsolete.

    It’s somehow related …

    Ed

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