CBS (maybe others) Poor Cable Quality?


#1

For whatever reason, CBS through a Comcast cablecard is showing up as if it's a poorly tuned OTA station. Constant pixelating, freezing, skipping, etc. No other channels that we watch have done this. Can anybody shed some light and provide a solution? It's happened on both recent Fire TV devices (pendant and new stick).


#2

You can check my.hdhomerun.com for the tuner status and contact your cable provider if it shows a bad signal


#3

I have noticed this too with fox. I can watch the channel side by side with a cable box that the company rents to you and I don't have issues on the box but still have issues on the channels app. Also noticed that fox isn't as clear as some other channels sometimes.


#4

Strange. What about in the HDHR app?


#5

Might be a network issue. The lower channels on Comcast (CBS, FOX, ABC, CBS, NBC, etc..) require more bandwidth because they aren't x264/Mpeg-4. I would try to record the channel (assuming you have a DVR setup), and see if you have issues at the same spot every time. Once you see pixelation, rewind and see if the pixelation is there again, or open the file in VLC to confirm the pixelation. If the pixelation occurs at the same time stamp every time, it's an issue with your cable connection. If not, it's likely a network issue.


#6

Well I can tell you for certain that it gets recorded that way and the glitches are "burned" in to the recording. It's not on and off nor different depending on the connection. That didn't really indicate to me that it was a cable issue, though. Couldn't that just as easily be the network, or a device on the network involved with the Channels process, struggling to deal with the higher bandwidth and resulting in degradation? It does appear to happen on the Fire TV as well as the Shield TV that does the DVR legwork, which are both in the same room, away from the HDHR. I may have to run some tests and see if the location/point is the issue.

It seems like I'm not the only one, so if others could chime in so we can diagnose this, that would be very much appreciated. My elderly father has been getting quite frustrated with his daily Colbert recordings all having some sort of glitch that many times makes portions literally unwatchable.


#7

Aman, I'll run some more tests, but it appears as if my CBS streaming rate tends to drop from 12-18mbps down to 3-6mbps when the glitches seem to occur. I haven't yet figured out why, or if that is in fact what's happening here. Any ideas or thoughts would be great.


#8

A drop in the rate means some packets are getting dropped over the network, which also explains why the picture gets corrupted.


#9

By now it's probably clear that this isn't a Channels related issue, so I don't expect a resolution to be provided, but assistance would definitely be appreciated as I've hit my wall on what I'm able to figure out, whether from Aman or anybody else who may be able to steer me in the right direction. To recap, one of the smoking guns is a major drop in streaming bandwidth on only the MPEG2 channels at or just prior to the glitches, indication a thus far inexplicable issue with streaming the high bandwidth (150mbps speeds at home).

I moved my Shield TV, so now I have my primary Google Wifi router hardwired to HDHR Prime which then wirelessly transmits to my Nvidia Shield TV. All of these devices are now right next to each other. It didn't change a thing. All MPEG2 stations are still frequently coming across as poorly-placed-antenna-like quality. It doesn't matter if it's live or recorded. Same glitches.

So now I'm trying to figure out if it's the Shield, the decoding of the clients (primarily new Fire TV 4K sticks), or wifi (hardware or software) configuration. Any direction I should go from here?


#10

Was the DVR wireless before too? First step would be to see if you can reproduce the issue on a fully wired network off the same switch. You can use http://x.x.x.x:5004/auto/v<ch> to download the stream to a computer that's wired to the same switch as the HDHR, and see if the streaming rate is constant and if the downloaded file has any glitches.


#11

Still love the speed at which you respond, shows just how much you enjoy what you do.

Yes, Shield TV (DVR) was always wireless. I had to eliminate the use of switches because it was causing issues (may have been VoiP related but I don't recall at the moment), but I suppose I can use it to at least troubleshoot just to see if it is in fact only happening over wifi. It's an inconsistent and unpredictable issue, so it takes some time and patience to troubleshoot, but I'll reply when I have something new to report or if I can't figure out how to do what you suggested.

I really, really appreciate your help with this. My parents get quite frustrated when trying to watch Colbert do his monologue, lol. They can't quite understand why things don't "just work". I'm not about to have a conversation with them about MPEG2...


#12

IMO you're trying to do things in the most problematical, most trouble-prone ways possible.

#1 - HDHR tuners must always use a wired connection.

#2 - DVRs must always use a wired connection

#3 - Those wired connections should be through Ethernet switches, not routers, and certainly not WiFi routers

#4 - I honestly don't know what a "Google WiFi router" is, but, knowing Google, it is not something upon which I'd care to stake the performance of my network--wireless or otherwise. If it's a Google WiFi Mesh router, that, right there, could be a good deal of the cause of your problems. Mesh networks and high-bandwidth video streaming are not a good combination.


#13

The problem is almost 100% due to WiFi. Low bandwidth h264 cable channels don't stress the WiFi much, but the high bitrate mpeg2 will put a strain on any WiFi system, and particularly on mesh based systems which have to download/upload the mpeg2 stream at the same time (thus doubling the bandwidth requirements).

When the WiFi can't keep up, it will drop some packets which is when you see the streaming rate go down (because some packets were lost) and why you will then see audio/video issues because parts of the stream are missing.


#14

I had typed something out previously to @jseymour but I'll get to that later. Instead, I had a question based on what you said.

We're all in agreement that it's likely wifi related. My question is, let's say I hardwire the DVR and record CBS. One would think that if wifi (or specifically mesh) is the issue, then the MPEG2 program would record perfectly. My question is, does the recording get saved as a different format than the original stream, or would the DVR then simply push out the EXACT same stream, at the EXACT same bandwidth, to the wifi clients when we try to play back, thus resulting in the same network strain and pixelation at that point?

(Hopefully that made sense.)


#15

The video stream is downloaded by the DVR and saved directly to disk with no modifications. If the DVR is hard-wired (or you use another computer to download the stream), it should record perfectly without issues. If it doesn't, then that means its not wifi but something with the wired network (bad cable, crappy switch/router, too many hops, etc).


#16

I'm referring to wireless playback of the recording via wifi-based clients (Fire TV) since those obviously can't be hardwired.

If it's still sent to them as a 14-18mbps MPEG2 after already being recorded, then it would likely still experience the same issue over the wifi mesh network, correct? If so, then my only answer, would be to eliminate the mesh network and move back to a slightly subpar single router.

(This is all assuming that everything works flawlessly for MPEG2 when I attempt it 100% wired, client included.)


#17

There is a big difference between live (i.e. coming from the HDHR) vs recorded playback (coming from a file on disk).

When watching live, there is a constant stream of bytes and no place to buffer them. So the only choice the HDHR PRIME has is to drop packets that cannot be delivered quickly enough. In this sense, the HDHR PRIME is very latency sensitive. So if your WiFi has a latency spike for any reason (weather, microwave turning on, neighbor using their hair dryer), the HDHR ends up dropping packets. If you're watching live you see pixelation, and if you're recording those glitches get recorded.

When watching recordings off of a disk, there is not the same problem with dropped packets. If there's a spike and some packets take longer, it's fine. The client can just wait and retry those packets, and if it takes long enough the player will pause to buffer. So if your recorded mpeg2 file is clean on disk, you will never have the same pixelation problem during recording playback. At worst, you will see the player pause/resume as it tries to buffer those bytes over the slow WiFi.

So the most important thing is that any clients that will be talking to the HDHR PRIME (i.e. definitely the DVR, and ideally also any other clients that will often be watching live tv directly) should be hard-wired and wired to the same ethernet switch as the HDHR.


#18

Ahhh, got it. That's a helpful bit of info on recorded playback vs live. That eliminates a lot of strain then. I've got the DVR hardwired now. Will test CBS recording quality and live quality using wired laptop, wired Shield client, and wireless Fire TV.

Last night I tested wireless live and wireless recording playback on MPEG2 networks using Fire TV in the same room as my main router and DVR (not a secondary mesh point) and it still glitched. Would this eliminate mesh in itself (not necessarily my wifi, though) from being the problem? I'm not familiar with the tech, but thought maybe since all equipment involved was connected wirelessly to the main router that in effect it was akin to standard wifi as opposed to being connected to one of the additional mesh points.


#19

If you're still having problems with the FireTV devices, Amazon does sell a wired ethernet adapter. (There are also other third-party ethernet adapters that work with the FireTV, but seeking them out isn't as easy as using Amazon's.8


#20

I wouldn’t think this would eliminate mesh as you can’t be sure exactly what the shield was associated to. Even if it’s in the same room, it may be associated to one of the mesh points.