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WHNE 13 subchannels

The technical side of broadcasting. Think IBOC is a sham? Talk about it here! How about HDTV? Post DX reports here as well.
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Circle Seven
Posts: 414
Joined: Fri Nov 13, 2015 10:53 am
Location: Fishing somewhere

WHNE 13 subchannels

Unread post by Circle Seven »

km1125 wrote: Fri Apr 01, 2022 11:04 pm It would be nice if they could allocate a few more bits to those subchannels that have motion video and less to those shopping channels
I moved this quote from the Detroit Metro discussion thread. As most know, the discussion entails multiple subchannels. The discussion apparently has sequined into the capacity of different subchannels.

Could someone explain how this works?
km1125
Posts: 3789
Joined: Thu Mar 14, 2019 3:09 pm

Re: WHNE 13 subchannels

Unread post by km1125 »

I'm not sure I understand your question. Is it "how do they allocate bandwidth to different subchannels?"?
Circle Seven
Posts: 414
Joined: Fri Nov 13, 2015 10:53 am
Location: Fishing somewhere

Re: WHNE 13 subchannels

Unread post by Circle Seven »

km1125 wrote: Sat Apr 02, 2022 11:43 am I'm not sure I understand your question. Is it "how do they allocate bandwidth to different subchannels?"?
Pretty much what I'm asking. How can one subchannel be faster than another. I think you're response on the other forum asked about some subchannels that streamed video be "quicker" or have more bits than the others that don't.
km1125
Posts: 3789
Joined: Thu Mar 14, 2019 3:09 pm

Re: WHNE 13 subchannels

Unread post by km1125 »

Of the total BW available - say 19MBPS, they have to divvy up those bits to each of the subchannels (and the corresponding audio channels). You also have some management "bits" like EPG that take up some bandwidth.

Usually, the bulk of the bits are allocated to the primary channel, which is also usually and HD channel and could be 1080I or 720P. That could be half the available capacity at around 9MBPS. The remaining amount (about 9MPBS) could be split between a couple SD channels, giving them about 4.5MBPS each. Those three channels wouldn't need to be compressed much and would deliver a pretty decent quality picture.

Now, lets say you add 8 more channels, all SD. You have to get those bits from somewhere, so you "steal" some from the primary channel and some from the two SDs. Even if you only allocated 1 MPBS to each of these 8 channels, (which would result is some pretty poor quality signals), you're taking HALF the bandwidth from the HD and the two SDs, making those pretty miserable to watch as well. WHNE doesn't have an HD in the whole group, but they're running 12 channels. Taking the max of 19MBPS and allocating evenly, that's about 1.5MBPS each, which is low but not unwatchable until you start getting a lot of motion or detail, then it gets to be a real problem.

So it's not about "quicker", it about the amount of bits every second. The bits are coming across still at 19MBPS, but each second each channel only gets 1.5 megabits, then it has to wait for the next second to get more. If the picture changes more than that from one second to the next, the viewer will notice it quickly.
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