Problems when playing recordings; corrupted recordings

Ugh.

Is your DVR connected via coax (black and circular) or ethernet (looks like a phone wire)?

I'd recommend switching to ethernet. If you can do this yourself, it's highly recommend.

If the problem still happens, I'd call 800-288-2020 and ask for technical support. As soon as you get an agent on the phone and have verified your account, let them know you're using ethernet and have already done the DVR swap. Letting them know this should save some steps.

I'm not entirely sure the problem is the DVR, considering yours was recently swapped.

But...an idea...how's the internet speed and reliability? Do speed tests continually show upwards of 270 Gbps?

The dvr is connected via ethernet. The dvr is used with a Roku TV, so I have a five port gigabit switch that supplies the DVR and the TV. 

We've been in our home ten years and have had U-Verse the entire time. This problem started about six months ago. 

I haven't been doing speed tests regularly but I will start doing that. Thanks for the suggestion. 

For troubleshooting purposes, could you connect the cable that leads to the switch from the Gateway directly to the DVR and allow a couple of recordings without the Switch and TV connected, then you can reconnect the switch back in line when you've done the test.  If the problem went away, then I'd try disconnecting the TV from the switch for a few recordings and see what happens.  Is there anything else connected to this switch, particularly a Wireless Router/AccessPoint or Extender?

Do you ever watch live TV through the DVR?  Do you not have any problems with that?

Can you confirm the link rate between the Gateway and your switch is 1000 Mbps (you could do that by checking that the transmit speed on the appropriate port is 1000000000 on this page: http://192.168.1.254/cgi-bin/lanstatistics.ha )

These are good suggestions that I will try. There are only two devices connected to the switch: the DVR and the TV. To me, the problem looks like the video player is trying to play a corrupted file, which is why I asked for the DVR replacement. We do occasionally see pixellation during live TV, but it's not the same effect we see when playing recordings. And how can you tell if the glitch is from the broadcaster or AT&T or from my internal network? 

My suggestions have been tempered by the fact that you've said you replaced the DVR already, otherwise that would be high on my list.  A bad replacement DVRs is not unheard of, though most of the stories of bad DVR replacements were when it just wasn't the DVR in the first place. ;)

It's hard to tell, which is why I usually ask to simplify to remove possibilities.  The non-DVR receivers, how well do they work when playing truly live content (by "truly live", I mean not paused/rewound/restarted, which relies on the DVR just like a recording)?

It may also be worth disconnecting the U-verse WAP and see if that corrects the issue... Again, simplify the network and see when the problem goes away.

If it happens when the DVR is connected with an Ethernet cable and that's all that's on the network, then see if you can swap the Ethernet cable (move the DVR to close to the Gateway for a few hours, maybe?).

The gateway shows that the link to the switch is 1 Gigabit. All Ethernet ports on the gateway are set to Auto-Detect. I connected the DVR directly to the gateway and recorded a few shows, which I still need to review but the first one I looked at plays back correctly. When the DVR is connected directly, the gateway shows the speed as 100 Mbps. The Speed Test page on the gateway shows four tests with upstream throughput of 375Mbps and downstream of 394. There is a large variance in latency, from a low of 8.5 to a high of 34.4. I noticed something on the LAN Statistics page. Port 4 is the DVR/TV/switch. Under "Detailed Ethernet Statistics" there are a huge number of discarded packets for the transmit side of port 4. Like 158 million! I don't know what time range that covers. Port 2 shows 1.2 million discards; the other ports have zero. I think I'll try swapping ports. 

Because this is such an intermittent problem, I need to change the network, record several shows and then watch them before I can tell if the change did anything.  

If your transmit dropped is more than 1% of your transmitted unicast+multicast, that's likely reflecting some sort of issue.  My Gateway has been up for a couple of months and I haven't reset the counters, and it looks like this:

The U-verse gear operates at 100 Mbps, so that's fine and doesn't actually use that much bandwidth, but I wanted to be sure that your link to the switch was at least that, and not 10 Mbps. :)

I've been running the DVR thru the switch, connected to port 3. The transmit discards are up to 8.1 million after four days. There must be a periodic reset of these stats because port 4 now shows zero discards. So far, all recently recorded shows have played correctly, as far as I can tell. The Roku TV is also connecting thru the switch, shared with the DVR. The latest speed test shows 375 upstream and 394 downstream. 

JefferMC said that discards greater than 1% of transmits might indicate a problem. Would that be a problem with the gateway? Should I ask AT&T to swap out the gateway? This gateway has been running for nearly ten years. 

On Monday evening, live TV on several channels was pixellating and freezing. We attributed that to solar storms, ha ha. Live TV looks normal today. 

I have not tried disconnecting the WAP since all the other TVs in the house run off wireless and I would be very unpopular. 

Thanks, everyone, for your help. 

It could be a problem with the Gateway, the switch or the Ethernet cable between them.  Typically it's the cable.  You can ask for a replacement Gateway to see if it's causing your video issues for that or other reasons.

An update for everyone: We have had no issues with corrupt recordings for several days. I've replaced the Ethernet cables between the gateway and the switch, and the switch to the DVR. I believe the major change that made a difference was switching the DVR to a new port on the gateway. However, the statistics page is showing transmit discards on port 3 are up to 24.5 million! It shows a total of 575 million packets transmitted, so the discard rate is 4.2%.  I may try to get on the phone with AT&T support and tell them about this. 

Thanks for all your help.