[mythtv] Mythtv and kernel 2.6.25

[Paulo Cavalcanti]

On Wed, Jun 25, 2008 at 6:09 AM, Paulo Cavalcanti <promac at gmail.com> wrote:

>
>
> On Tue, Jun 24, 2008 at 2:31 PM, Andrew M. Bishop <
> amb at gedanken.demon.co.uk> wrote:
>
>> "Paulo Cavalcanti" <promac at gmail.com> writes:
>>
>> > On Sun, Jun 22, 2008 at 6:56 AM, Andrew M. Bishop <
>> amb at gedanken.demon.co.uk>
>> > wrote:
>> >
>> >> "Paulo Cavalcanti" <promac at gmail.com> writes:
>> >>
>> >> >> > I am having problems to make mythtv work with kernel 2.6.25
>> (Fedora 8).
>> >> >> >
>> >> >> > The problem seems to be my capture card, a Prolink Pixelview.
>>
>> >> I had the same problem and stayed on kernel 2.6.24 with my bttv cards.
>> >> I did some investigation and the problem seems to be related to the
>> >> changeover to V4L2 in 2.6.25.
>> >>
>> >> This message http://lkml.org/lkml/2008/1/6/83 describes a patch to the
>> >> bttv driver, but if you look at the 2.6.25 kernel source you will see
>> >> that it isn't there.  If you apply this patch (like I tried) then it
>> >> will get further, it won't lockup but I didn't get any video either.
>>
>> > I rebuilt video4linux from ATrpms using today's snapshot,
>> > and it worked.
>> >
>> > Well, almost. If I try mythtv Live TV after rebooting, I get a green
>> screen
>> > (but no lock).
>>
>> This is what I got when I tried my home-made patch with the raw 2.6.25
>> kernel - a green screen instead of a picture.
>>
>> I enabled all of the debugging that I could find and this was the
>> error message that I was getting:
>>
>> v4l1-compat: VIDIOCMCAPTURE / VIDIOC_S_FMT: -16
>>
>>
>> To bring this back on topic for mythtv-dev: I think that the problem
>> is that mythtv uses partly or mostly V4L1 and with newer kernels this
>> is provided only by a compatibility layer.  The VIDIOCGMBUF and
>> VIDIOCMCAPTURE ioctls (which are the ones causing the two problems
>> here) are both V4L1.  If the V4L1 layer ever goes away then mythtv
>> will need to switch over.
>>
>>
>> > However, If I run mplayer before using mythtv, Live TV works just fine.
>> > Maybe this is related to the nvidia driver I am using. I did not try the
>> > latest one (173.14.09).
>> >
>> > I will ask Axel to make video4linux (20080622) available to the public.
>>
>> Probably this configures the tuner in some way that is different from
>> mythtv and the settings stick.
>>
>
>
> Hi,
>
> ATrpms has the updated video4linux tree (20080622).
> Therefore, it is easy to test without getting locks. One just need
> to install the appropriate video4linux kmdl.
>
> I also contacted Mauro Chehab:
>
> > Hi, Mauro
> >
> > I almost got mythtv working again with bttv and kernel 2.6.25
> >
> > http://mythtv.org/pipermail/mythtv-dev/2008-June/062323.html
> >
> > http://mythtv.org/pipermail/mythtv-dev/2008-June/062325.html
> >
> > However, I have to run an mplayer (second link above) script before
> > using mythtv with Live TV. Otherwise, I get only a green screen.
> >
> > Can you give me a clue why the script fix the problem?
>
> >> Weird. There are some possible reasons for a green screen:
>
> >>        1) xv troubles. This sometimes happens if you are using a
> proprietary
> >> driver, like ati or nvidia. Don't use those drivers, or you'll have
> troubles
> >> displaying tv;
>
> >>        2) Tuner didn't load firmware properly (if you're using
> xc2028/xc3028
> >> or xc5000);
>
> >>        3) Some analog tuners only work if you set it first to a high
> channel.
> >> Kernel driver already sets freq to 400KHz, so I suspect that this is not
> the case;
>
> >>        4) There are some failure at the negotiation process between
> MythTV and
> >> your board. Since boards like bttv supports several different formats,
> maybe a
> >> bug at MythTV is preventing it to select the proper format. Maybe some
> API
> >> non-compliance could prevent MythTV to find the proper format;
>
> >>       5) a kernel bug ;) Since it is working with other userspace apps,
> I
> >> don't think this is the issue.
>
> >> I've just added a small patch at linuxtv repository that will allow you
> to
> >> enable ioctl debug at the driver.
>
> >> Please try first to use the non-proprietary driver (if you're using).
>
> >> If still not working, you'll need to retrieve the last version of the
> driver at:
> >>        http://linuxtv.org/hg/v4l-dvb
>
> >> after compiling/installing, you'll need to do:
> >>        modprobe bttv bttv_debug=3
>
> >> Please try to run mythtv without using the mplayer command and send us
> the
> >> output of "dmesg" command.
>
> >
> > Thanks, and keep up with the very good work at video4linux.
>
> >> Anytime.
>
> As I said before, running mplayer for watching TV just once (after
> rebooting),
> fix the myth Live TV.
> My myth seems to be working very well with kernel 2.6.25 after doing that.
> I can record, edit, etc ...
>
> I tried running other programs, such as xawtv, tvtime, but only mplayer
> fixed the
> issue with the Live TV.
>
> Probably, I will only have time to debug the bttv driver next week.
> Although I use an nvidia card (GeForce 7600 GS), I do not think the problem
> is
> because of the proprietary driver. If anyone can run without loading the
> nvidia driver (but using the nv driver), I would like to hear the result.
>
> Thanks for the info.
>
>
>
This issue is fixed. I submitted a patch for ATrpms that avoids the "green
screen".

It is also necessary to use the latest kernel 2.6.25:

Linux version 2.6.25.10-47.fc8


> Hi, Axel

> I am attaching a patch that
> fixed my problem with the bttv driver and mythtv,
> when using kernel 2.6.25.

> The latest versions of the kernel do not lock
> mythbackend anymore, but the screen was completely green
> while watching Live TV (or recording).

> The patch is very simple (just comments a test) and forces v4l2 for all
bttv models.

> In fact, I got it from here:

> http://www.gossamer-threads.com/lists/mythtv/users/337685<http://www.gossamer-threads.com/lists/mythtv/users/337685>

> Axel, can you apply it in future mythtv releases?
> I am also attaching the new spec file.

> Thanks.

-- 
Paulo Roma Cavalcanti
LCG - UFRJ
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