Rpi3b front-end 0.28 set-up experience and observations

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Manhole
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Rpi3b front-end 0.28 set-up experience and observations

Post by Manhole » Sun Mar 26, 2017 6:51 pm

I started talking about my experience in the segfault thread, but I am moving it here because my issues turned out to be totally unrelated.

I've had a 0.28 chromebox backend running for many months now. I've been using either osmc or libre-elec front ends on rpi3s, and one windows pc with kodi occasionally connecting. The performance has been good, but the video signal has been choppy at times, and only recently became totally unacceptable. I decided to try using myth front end lite on an rpi to see if that cleared up issues.

I used the setup wiki pages, and ran into an issue almost immediately with front end failing to connect to the database. Long story short, this turned out to be the bind address for the sql database (but I took a meandering road to determining that). With the database sorted out, I started the front end set-up for real. That process was fairly quick and painless, but resulted with even worse video quality than the kodi frontends (even with recommended settings). Freezes, video artifacting, audio drops and stutters etc. It was quite bad, and it seemed that certain channels were affected worse than others. The strange part was that none of the TVs (or the old tivo that's still hooked up) had any issues with the same signals. This ultimately became my clue for what the issue was...

My hd homerun connect tuner was basically high signal strength, but borderline signal quality on several (problematic) channels. After some digging, I discovered that many TVs apparently have some sort of signal processing or low level amplification before displaying the picture, which would explain the difference. When I put a super cheap amplifier right before the hdhomerun, video quality dramatically increased on all frontends, all channels. Kodi and mythfrontend are now working better than I've ever managed before. Now that I have this mythfrontend set up to play with, I'm going to explore it a bit further to see what I prefer.

Ultimately my mythfrontend setup became the recommended:
  • 256GB vid memory split (had this higher, but I believe it led to freezes after roughly 30 mins, and it's just not necessary)
  • openmax high quality video (had to use normal when my video memory was too high)
  • alsa default for audio

Strange things I've encountered:
  • Theme Chooser populated a list with many options to choose from, but after downloading/installing one (aeon nox), the list was reduced to the already installed themes. I no longer have access to the other options listed before.
  • Several setup options have missing images in the menu. This isn't important but I figured I would mention it.
  • I'm getting a bit of strange video artifacting that looks related to interlacing if I had to guess. I haven't found any options that seem to affect it. It's minor and something that my household can deal with. But I think it's worth mentioning. It basically looks like slightly offset horizontal shifts in the image in certain spots (so a straight line becomes zigzagged). This ultimately may not have to do with myth tv specifically, but the problem is not there when watching a stream directly from the tuner to vlc.
I'll update more if I discover anything. In the end, I've had a lot of fun toying with these set ups, and I'm grateful for all the work that's gone into it. It's pretty amazing that someone like me can throw something like this together. Great work!

Manhole
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Re: Rpi3b front-end 0.28 set-up experience and observations

Post by Manhole » Sun Mar 26, 2017 6:59 pm

oh and thanks PGBennett, your responses have been very helpful!!

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pgbennett
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Re: Rpi3b front-end 0.28 set-up experience and observations

Post by pgbennett » Mon Mar 27, 2017 4:45 pm

Theme Chooser populated a list with many options to choose from, but after downloading/installing one (aeon nox), the list was reduced to the already installed themes. I no longer have access to the other options listed before.
In the theme chooser screen, try pressing M and select the refresh option.
Several setup options have missing images in the menu. This isn't important but I figured I would mention it.

This may be a problem with the theme you are using. Which theme do you see this in?
I'm getting a bit of strange video artifacting that looks related to interlacing if I had to guess. I haven't found any options that seem to affect it. It's minor and something that my household can deal with. But I think it's worth mentioning. It basically looks like slightly offset horizontal shifts in the image in certain spots (so a straight line becomes zigzagged). This ultimately may not have to do with myth tv specifically, but the problem is not there when watching a stream directly from the tuner to vlc.
Is this tearing? (example http://jmichelgarcia.com/wp-content/upl ... earing.jpg). I have never seen this on raspberry pi. It can happen with some VDPAU setups if you have composite enabled and in other situations where the display driver is too slow. Are you seeing this with OpenMax video profile?

Manhole
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Re: Rpi3b front-end 0.28 set-up experience and observations

Post by Manhole » Wed Mar 29, 2017 9:49 pm

Theme chooser was indeed "fixed" for me by hitting M. Thanks

The theme with missing menu images was terra, the default one.

The video issue is not tearing as in your example. The image looked like it had tiny sine wave distortion (if a vertical line was drawn on screen, it would look sort of wavy) but it wasn't perfectly rock solid. What I mean by that is that it would sort of shift around as the image changed. Also it was most obvious on sports, and there was more to it because the crowd in the background would often be weirdly artifacted and the player being tracked would be less of an issue.

As it turns out, I do believe my issue was due to an interlace setting on an rpi running kodi with mythtv plugin. It was not saving my interlace option from "off" to "auto" for some reason. I had to go to another channel that had it set to "auto" and hit "apply setting to all media" or something like that to fix it on the problematic channel. In retrospect I think it may have never been happening on the mythtv frontend unit I was setting up, I was just messing with too many things at once. In any case, I believe this is now a non issue in my setups.

However, I did start getting slight drop outs (video cuts to silent black screen briefly) on the mythtv frontend that I was not experiencing on the kodi box which is also still running. I seem to have better results going back down to openmax normal. Does this make sense or is it just placebo? The dropouts happen to be on some of my weaker stations (100%+ signal strength, 75%+ signal quality, 100% symbol) which are my go-to test cases. After dropping to openmax normal the micro dropouts have not been occurring on any channel I try.

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Re: Rpi3b front-end 0.28 set-up experience and observations

Post by pgbennett » Thu Mar 30, 2017 8:19 pm

Terra has always been missing a bunch of images, on all frontends. I suggest using another theme.

I do not know what would cause your blank screen dropouts. I do not think that openmax normal vs high quality would cause that. With Openmax normal the On Screen Display will be inferior in quality. With Openmax normal it will use less GPU memory. I suggest you switch back to Openmax High Quality and see if you still have problems. There may be something wrong with the specific recordings. Try them again and see if the blank screen always happens at the same place.

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