[mythtv-users] MythTV 29.1 nVidia video jump hesitation with 5.15 kernel

[Tom Dexter]

On Tue, Jan 25, 2022 at 10:57 AM faginbagin <helen.buus at gmail.com> wrote:
>
> On 1/24/2022 2:16 PM, Tom Dexter wrote:
> > This is a tough one, and I tend to doubt anyone will have any ideas,
> > but I figured I'd throw it out there:
> >
> > For reasons I won't get into, I'm still running MythTV 29.1. This is
> > under Gentoo and the frontend is an x86 (32 bit) machine with a GT 430
> > nVidia card, using nvidia-drivers-390.147, and using vdpau. Currently
> > I have both the 5.10.93 and 5.15.16 Linux kernels installed. When I
> > use the 5.15 kernel...and ONLY with that kernel...I'm getting odd
> > video/audio hesitations when jumping forward or back, and only in
> > MythTV. That is, I can't reproduce this in xine or mpv. This occurs
> > both with TV records as well as h264 videos in browse mode reading
> > from the local disk.
> >
> > Specifically, when I jump forward or back, there's a momentary
> > hesitation before the audio kicks in, and during that short time, the
> > video gets a little wonky, like it's slowing down for a second. In the
> > 5.10 kernel everything's fine. Sort of really sucks. For now I'm just
> > sticking with the 5.10 kernel. If anyone has any ideas I'd appreciate
> > it. Thanks!
> >
> > Tom
> >
> This sounds like a kernel regression. If you're interested in a
> challenge that may or may not pay off in a solution, I think you'll need
> to do some kernel bisecting. By that I mean, first test if the problem
> exists in 5.13. If it does test 5.12, otherwise test 5.14. Once you know
> which kernel introduced the problem, then do a git bisect on that kernel
> branch. If you can identify an offending commit, you can report it to
> the appropriate kernel development arm and hope someone is interested in
> fixing it.
>
> I actually had some luck in getting a problem fixed with an intel igp on
> a 32 bit laptop at the end of 2018. Here's the bugzilla link:
> https://bugs.freedesktop.org/show_bug.cgi?id=107600
> But that was three years ago.
>
> I also had a problem with a radeon igp on a different 32 bit laptop. I
> went through the bisecting process and found a workaround with a kernel
> command line option as a result of tracking down the offending commit.
> So, I never needed to report what I considered a bug, because it was
> clear from mailing list and bugzilla discussions, that the kernel
> developers involved didn't think it was a bug, that the real problem was
> old buggy hardware.
>
> I'm still on v29 because I've still got hardware that works and isn't
> supported by newer versions of mythtv or kernels. BTW, kernel 4.19 is
> under long term support and might be a more reliable kernel option for
> older hardware. Debian bullseye is on 5.10, and still supports 32 bit,
> so that should bode well for its use on gentoo with 32 bit hardware.
> I've got a circa 2002 pentium 4 desktop I use as a mail, web and file
> server. I've done some testing of it with bullseye. So far, so good.
>
I suspect that the issue is likely more about flaky support for 5.15
in that legacy 32-bit nVidia driver, and my odds of getting anywhere
with that are probably very slim.

As to the kernel version, 5.10 is under long term support as well, so
I'm probably best just sticking with that to resolve this one. Thanks!

Tom