XG1V4 box HDMI handshake problem

Right, i don't have a 4k tv.  it's LG, has 480p, 720p, 1080i, and 1080p options, and the x1 box automatically chooses: (as shown on the video output resolution) "1080p60hd (best available)"

i know the the x1 will upscale, by why make the box/tv upscale, when there are settings to choose that set the scale?  or, that the box finds and sets as "best available?"

I thought you said you didn't have a 4k TV.   So 720p is the best resolution for many/most things (for reasons too complicated to explain here - look up why it is used for sports broadcasts).  Even if you do have a 4k TV unless you are watching 4K content your expensive TV can generally upscale as well as the X1 box.    Xfinity only has a tiny amout of 4k programming (updated regularly here: https://www.xfinity.com/support/articles/uhd-4k-faqs) along with the Amazon/Netflix apps that are also probably available on your TV or other devices you own.

i'll have to change it to 720p tonight before i  shut the tv off, then in the mornin when i turn the unit back on see what happens?  but if it only works  on 720p, what's the sense?

Apparently your TV is offering a 'best available' that doesn't actually work.   Otherwise you wouldn't be having problems.   I'm suggesting trying something that might work.   And since most of the content from Xfinity is delivered at 720p, won't harm what you see.    Your local broadcast channels might be carried at 1080i but 1080p60 is something just made up by the box - which would be OK if the TV accepted it, but not really an improvement and not worth dealing with problems over.

as i said yesterday, "set the tv to 720p last night before turning the tv off for the night.  turned it on this morning and same flashing in and out for about 8 minutes before the picture locked.

i didn't think it would make much difference.  i have been comcast customer for 16 years, have never had an issue, have never had a connection issue, until about 3 weeks ago when this all started.  nothing different in the equation, other than the problem.

tv is wall mounted, only way to to check current hdmi cable at tv is to have someone remove tv from wall mount so that connection can be checked, but so no reason why the connection would all of a sudden change when nothing behind the tv has been touched/changed?

as to trying a different hdmi, i got to run to the store, pick one up, wait till tonight when i'm shutting down, turn tv off, unplug hdmi from box, plug new cable in to box and then to hdmi on side of flat screen.  and then wait till morning and turn set on and see what i get.  more then..thanxz so far for the conversation, regardless...lol

but isn't it strange that every morning there's this problem, for about 8 minutes, then the picture locks in.  no problems the rest of the day.  have turned the tv off for short periods, 30/45mins to an hour, no problem when turning baack on.  have shut it off for over 2 hours and no problem turning back on, picture instantly.  turn it off over night, back on in morning, same problem.

so will try the new cable in the morning.  hopes it not the hdmi, will have to call someone in to change it out for me.

I've had the HDMI ports go out on a TV - it happens.  I was able to continue using it for a while with component cables but eventually replaced it.

i would hope that it's not a  handshake problem, and a simple hdmi cable or port, but if my post isn't a handshake problem, then others in this thread aren't either i guess?  how did you come to this conclussion, just curious?

Real handshake problems would never display anything.  Most of the posts here are about having 4k settings and failing to display when the TV and/or X1 box have been in sleep/low power mode and have different timing as they wake up.  Generally they are OK if you power cycle one or the other or both, or just disconnect/reconnect the HDMI cable, or simulate that by switching the TV input to another port and back.  Some have found a permanent solution, some haven't.

brand new hdmi cable, plugged in to different hdmi port...............same problem, 9 minutes of flashing from black screen to picture, to black to picture every second, for 9 minutes.  so, what's the next guess?  hdmi motherboard ?  new oled tv on the horizon..............

refresher:  a little over 3 weeks ago, turning on the tv the first time in the morning, the problem started.  9 minutes of the flashing from black screen to the broadcast picture, flashing back and forth every second, for 9 minutes.  then the picture would lock in, and no problem for the rest of the day, even after turning the tv off at various times during the day, then back on when we got home or wanted to watch tv, no flashing, instant broadcast picture.  the next day, when i turned on the tv and the flashing started, i unplugged the x1 box, waited 20 seconds, plugged it back in, tv showed the restart process, and when it was done and booted up i had my picture.

the 3rd morning when it did that, i unplugged the hdmi from the box, plugged it back in, no change, still flashing.  unplugged box, plugged back in, boot process, broadcast picture there.

had comcast out on 4th day, swapped box out for the new one, next morning turned on tv, flashing still there.  so not the box.  did some searching online for other's with same issue, came here, started reading.  finally decided to swap hdmi cable out, and try new hdmi port, which brings me to where i am this morning, and will be looking for a good deal on a samsung 65" oled.