Roku Premier 4620RW software v. 9.20.4807. HDMI passively routed through A/V amp.
[Since I subscribe to Dish satellite service, I use a channel's Roku app to watch their material, not a streaming service like Hulu or the like. That's why I have to suffer through blocks of commercials when I watch their TV programming.]
I was watching some older TV program material on both FX and SyFy Roku channels yesterday and both channels exhibited exactly the same problem.
During a program, a few seconds before the start of a block of commercials, and then again a few seconds before the end of the last commercial, the audio and video will drop out and the TV shows "no signal." The audio and video will then resume on their own within another few seconds. In the case of the dropout at the end of the last commercial, the recovery occurs late enough that the first second or two of the program audio and video are missed. The same probably happens at the start of the commercial block, but being a commercial, I really never notice what I might have missed.
Occasionally, on the return to the program material at the end of a commercial block, the image colors are wrong. The only way I've found to restore the colors is to stop the playback, go back to the app and then resume playback.
Once the audio and video have recovered, the program material display is clean until the next commercial block.
I've rebooted the Roku, the A/V amp and the TV with no effect on the problem.
Since I don't use the Roku device to watch TV programming very often, this problem may have existed for some time without my ever running into it.
I've never seen anything like this on the HBO Now or Amazon Prime Video apps.
Took your suggestion and had some interesting results.
The original setting was "Automatic" and In testing, I saw that the program data was 24p, while the commercials were at 60p. Just guessing that in "automatic" any change in the data caused the device to do quite a bit of fiddling to determine what the proper mode should be, which probably took a fair amount of time.
Switching the mode to be fixed at 1080p, there was still an audio and video dropout, but it was much shorter and the switch to 24p at the end of the commercial block was clean without any loss of program video or audio. So I'm going to mark this problem as solved.
I don't know what will happen if I ever run into 720p programming; it seems unlikely that the Roku box can upconvert on the fly. I'll wait until that happens to try to find a solution.
Thanks!