High Network Usage / Streaming Rate

ATSC 3.0 Forum
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tzr916
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High Network Usage / Streaming Rate

Post by tzr916 »

Just got my new 4k OTA tuner. I'm surprised that the "streaming rate" for the tuners is always ~20Mbps/channel, no matter what channel I go to HD or SD! I know the actual bitrate of these channels is far less because they have several sub-channels. This means, if I'm recording 4 channels from this device, my network usage will be +80Mbps! Meanwhile, when using HDHRP cable card, network usage / streaming rate of a tuner ranges from 3Mbps to 6Mbps per channel (more accurate to the actual bitrate).

So, how and why is the "streaming rate" always ~20Mbps/channel with this device? Is there some re-packing being done? Why is not the actual bitrate of the tv station? And when the 4k channels arrive, will this go UP even more?

EDIT: Never mind, I guess the device just streams the entire 19Mb station (all subchannels), regardless of which subchannel is actually being watched/recorded.

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NedS
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Re: High Network Usage / Streaming Rate

Post by NedS »

I believe the plan is to try and make it possible to stream at least two channels per ATSC 3.0 tuner, so what you're seeing might be the result of that starting to be set up. Nick will have a better (and more accurate) answer, though.

nickk
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Re: High Network Usage / Streaming Rate

Post by nickk »

Which app are you using?

tzr916
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Re: High Network Usage / Streaming Rate

Post by tzr916 »

Jriver Media Center on Win10.

tzr916
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Re: High Network Usage / Streaming Rate

Post by tzr916 »

nickk wrote: Wed Oct 14, 2020 1:40 pm Which app are you using?
Jriver support says this is due to "Microsoft's bda architecture". Is this really the case? Does all third party software behave this way for Silicondust ATSC antenna tuners? Maybe there's some secret sauce you can give them on this topic?

https://yabb.jriver.com/interact/index. ... #msg883215

signcarver
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Re: High Network Usage / Streaming Rate

Post by signcarver »

Typically only the way jriver does it, though some other software may or may not also choose to (and may give users a choice). Most modern software with modern tuners won't even need the bda drivers as they use http streaming.

nickk
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Re: High Network Usage / Streaming Rate

Post by nickk »

The Microsoft BDA architecture supports PID filtering and the HDHomeRun driver supports this feature, but most apps don't make use of the feature.

Nick

tzr916
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Re: High Network Usage / Streaming Rate

Post by tzr916 »

So it seems any windows 10 software that uses MS BDA (eg JriverMC) should be able to implement PID's so that only the subchannel's stream is sent to the PC. Now, if they choose to utilize this method, would that somehow prevent simultaneous recording of two subchannels from the same channel using one tuner? example:
Tuner 0 - record ch 35.1
Tuner 0 - record ch 35.2

jasonl
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Re: High Network Usage / Streaming Rate

Post by jasonl »

If PID filtering is used, the app can add and remove individual PIDs or ranges of PIDs, so they could in theory stream 35.1 and 35.2 but not 35.3 and 35.4, saving that bandwidth. Most apps don't bother because the bandwidth savings rarely matter and it's a ton of work to implement.

tzr916
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Re: High Network Usage / Streaming Rate

Post by tzr916 »

Personally I don't have any use for subchannels whatsoever, and wish they had never come about. All they've done for me is reduce the quality of the picture on the Main HD channel. That ship sailed a long time ago. Today, I am much more interested in why an app would stream the whole 19Mbps channel when PID's can be used to filter just the one that's being requested for use. Is it really that much more work to implement?

emveepee
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Re: High Network Usage / Streaming Rate

Post by emveepee »

Perhaps less important when there are 4 tuners but from a PVR experience it there is obvious benefit to being able to record or watch multiple sub-channels at the same time.

Martin

jasonl
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Re: High Network Usage / Streaming Rate

Post by jasonl »

tzr916 wrote: Fri Oct 30, 2020 3:59 pm Personally I don't have any use for subchannels whatsoever, and wish they had never come about. All they've done for me is reduce the quality of the picture on the Main HD channel. That ship sailed a long time ago. Today, I am much more interested in why an app would stream the whole 19Mbps channel when PID's can be used to filter just the one that's being requested for use. Is it really that much more work to implement?
Yes. Instead of just tuning a channel and being done with it, the application has to tune the channel, request to receive the lowest level data, parse that to find the mid-level data, request that, parse that to get the information for the audio and video tracks, then request those. When supporting multirec, it has to keep an internal record of which ones are in use for which channel, so when you change channels or have a recording end, it can drop those without affecting anything else that might be going. It also really only benefits the HDHomeRun, since no one cares about bandwidth usage for a USB or PCI-E tuner.

There's also an in-between method supported where the app can request just a single program and let the device set the filter, which is what SageTV uses. It's more work than not using it, but less working than the app implementing the filter. Of course, at that point, they might as well just use HTTP streaming and get something that's a bit more resilient.

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