[mythtv-users] Display weirdness

Sat Oct 17 22:52:26 UTC 2020

On Sat, Oct 17, 2020 at 5:33 PM DryHeat122 <dryheat122 at gmail.com> wrote:

> On Sun, Sep 13, 2020 at 12:59 AM Stephen Worthington <
> stephen_agent at jsw.gen.nz> wrote:
>
>> On Sat, 12 Sep 2020 20:05:05 -0700, you wrote:
>>
>> [snip]
>
>
>
>> >Today a new problem cropped up.  From the program guide I started ESPN HD
>> >from the "watch this channel" menu item to watch Lakers v Rockets.
>> HDPVR2
>> >started fine but the picture was shrunk to about half the size of the
>> >monitor. Esc and try again, same result.  Rebooted, and same result.  I
>> >noticed when it was starting from the program guide it showed the ESPN HD
>> >icon, but another tv icon with SD below it.  So  somebody thinks they're
>> >getting a SD signal. You can get HD video off component video outputs of
>> >the HDPVR2, right?  Here's the kicker.  After watching the game on
>> another
>> >system, I went back and tried ESPN again on the Myth box as above. Now I
>> >still get the TV/SD idon on startup but the picture is full screen.
>> WTF?!?
>>
>> There can be a number of things that can cause this, including bugs.
>> But the things to look at are how you have the config set up for
>> playing video.  There are options that allow the video playback to
>> change the video mode separately from the GUI screens - see Setup >
>> Appearance > Separate modes for GUI and playback.  If that is set,
>> then whenever you are playing video, the content of the video is
>> matched against your playback profiles and the settings for the
>> matching profile are applied.  This can also cause xrandr commands to
>> be sent to the X display to get the display to change mode to a mode
>> that matches the video that is being played.  Such mode changes can
>> happen if the video being played changes mode in the middle (eg sport
>> is 720p, but it changes to 1080i for the ad breaks).  The available
>> mode changes are the modes that X lists in its Xorg.0.log file when it
>> starts up.  You can get a problem that there are modes available that
>> are not actually what you want for your screen.  So if the recording
>> is 576p, for example, the matching mode may be only for displaying on
>> 1/4 of the screen, when it should be set up to reprocess the frames to
>> a 1080 screen size.  I have just been fighting a slightly different
>> version of this problem where I do not want any interlaced modes used
>> as when there is onscreen GUI overlaying video output, the GUI part of
>> the display gets distorted by the interlacing.  The solution I am
>> currently trying for this is to tell X not to use the EDID sourced
>> modelines (and lots of other modeline sources) and just to use the
>> modelines I have specified in my xorg.conf file.  I turned on this
>> option:
>>
>> Section "Screen"
>>   Option    "ModeDebug" "true"
>> EndSection
>>
>> so that X logs details of all the modes it sees and edited the output
>> of that to create the modelines I wanted, then disabled all the other
>> modes.  Along the way, I had some modes from other sources still
>> enabled that caused exactly what you are seeing where the video only
>> used part of the screen.  After turning off those modes, it now seems
>> to be working well, but it has only been a few days so far and I need
>> to test it on various video files to be sure.
>>
>> You can find out what mode your screen currently is in by opening a
>> terminal and using xrandr.  I hate xrandr - it is difficult to use and
>> does not actually allow you to see the modes in the way they are
>> reported in X's logs, but the required information is there.  So when
>> you next have this problem, make sure you have the ModeDebug option on
>> first, then run "xrandr" and see which mode has the * character by it,
>> telling you that is the current mode.  Then match that to the modes
>> reported in the X logs, and see if there is a problem.  You may need
>> to disable that mode so a better one gets chosen, or you may need to
>> use an xorg.conf option to set scaling for that mode so it will fill
>> the full screen.  Your TV may also have a menu or remote key that will
>> get it to display information about its current screen mode.
>>
>> BTW You have not said what video card you are using.  I am using an
>> Nvidia GT1030, so things may work differently if you are using Intel
>> or AMD.
>>
>
> Found some time to get back to this issue.   All the problems with screen
> sizing were resolved when I updated my Nvidia drivers (video card
> is Geforce 8400 GS Rev. 2).  Now the issue is jankey/stuttering video/audio
> when watching live TV.   It's odd because if I record these same channels
> then play the recording everything is fine.  The only problem is when I'm
> trying to watch live.
>
> I am still getting the SD symbol when I "watch this channel" on HD
> channels where I encounter the stuttering.  Maybe it's occurring because
> the system is trying to down-sample the HD to SD and the processor can't
> keep up?
>
> I think this advice pertained to the screen size issue, but just in case I
> checked setup and  "Separate modes for GUI and playback" is not enabled.  I
> also had a look at  Xorg.0.log for modes listed, and there don't seem to be
> any except auto-select.  Here is the output of  cat Xorg.0.log | grep mode:
>
> [     7.808] (==) Matched modesetting as autoconfigured driver 2
> [     7.828] (II) LoadModule: "modesetting"
> [     7.828] (II) Loading /usr/lib/xorg/modules/drivers/modesetting_drv.so
> [     7.829] (II) Module modesetting: vendor="X.Org Foundation"
> [     7.832] (II) modesetting: Driver for Modesetting Kernel Drivers: kms
> [     7.841] (WW) Falling back to old probe method for modesetting
> [     8.331] (==) NVIDIA(0): No modes were requested; the default mode
> "nvidia-auto-select"
> [     8.331] (==) NVIDIA(0):     will be used as the requested mode.
> [     8.368] (II) UnloadModule: "modesetting"
> [     8.368] (II) Unloading modesetting
> [     8.375] (II) NVIDIA(0): Setting mode "DFP-0:nvidia-auto-select"
> [     8.550] (**) Option "xkb_model" "pc105"
> [     8.553] (**) Option "xkb_model" "pc105"
> [     8.571] (**) Option "xkb_model" "pc105"
>
>
> Maybe there are no modes because I don't have ModeDebug set as suggested,
> but I'm not sure how to do that.
>

MythTV has long had live TV issues with stutttering, etc.  Just a shot in
the dark - have you started live TV and immediately pressed back (left
arrow) to see if it stops?

Just making sure you have not tried this already - a lot of improvement was
made by Peter Bennett a while back, but it still plays best when you let it
(I'll call it, for simplicity) fill the buffers.

If you have tried this, then please, disregard.

-Greg

-Greg
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