[mythtv-users] Getting lots of jitter with version 0.24

Justin Johnson justin.johnson3 at gmail.com
Tue Nov 23 04:13:52 UTC 2010


On Mon, Nov 22, 2010 at 6:36 PM, John P Poet <jppoet at gmail.com> wrote:
> On Mon, Nov 22, 2010 at 4:23 PM, Justin Johnson
> <justin.johnson3 at gmail.com> wrote:
>> On Sun, Nov 14, 2010 at 4:06 PM, Justin Johnson
>> <justin.johnson3 at gmail.com> wrote:
>>> On Sat, Nov 13, 2010 at 8:25 PM, Kevin Ross <kevin at familyross.net> wrote:
>>>>
>>>> Unfortunately, no I haven't.  I haven't had time to try to diagnose the
>>>> problem, so I've just been putting up with it.  I wonder how many other
>>>> HD-PVR users are observing the same.
>>>
>>> I've investigated this a little further, after having a couple
>>> recordings take place. I only see the jitter in LiveTV on progressive
>>> scan video, my recordings are fine. In fact, if I enter livetv, I
>>> observe the jitter. If I then hit the record button, then play the
>>> same recording from the recording list, the jitter is gone. I've
>>> confirmed this in the logs as well as visually.
>>> It looks like the framerate in LiveTV is being detected as 25fps, and
>>> the display is set to match. But the video is actually 30fps and so
>>> the display is at the wrong refresh rate. If I force the display rate
>>> to 60Hz then it displays fine, of course 24fps content is wrong.
>>> So, the question is, why does myth incorrectly detect the framerate of
>>> progressive content in LiveTV only?
>>> As a temporary workaround, I've removed the 50Hz modeline from
>>> xorg.conf and the issue is fixed. Since I don't plan on watching any
>>> PAL content, I don't think this should be a problem, but it would be
>>> nice if it were fixed in the future.
>>>
>>> --Justin Johnson
>>>
>>
>> OK, I lied, this does not work around the issue, at least not fully. I
>> still see the same behavior when playing back at 1.5x (I like to watch
>> most shows sped up, it dramatically decreases the amount of time in
>> front of the tv). Again, only with progressive content. Mythfrontend
>> drops a number of frames every 0.02 seconds, which causes significant
>> stutter. Any ideas for troubleshooting, users?
>
>
> Try these patches against 0.24:
>
> http://svn.mythtv.org/trac/attachment/ticket/7964/mythtv_smoothsync.13.patch
> http://svn.mythtv.org/trac/attachment/ticket/7964/smoother-vsync-audio.11.patch
> http://svn.mythtv.org/trac/attachment/ticket/7964/smoother-vsync-vsync-opt.11.patch
>
> They do wonders for progressive frame-rate timestretch playback.
>
> Unfortunately, something in trunk has broken the effectiveness of
> these patches, but they work great with 0.24.
>
>
> John
> --
> A: Because it messes up the order in which people normally read text.
> Q: Why is top-posting such a bad thing?

While the log still shows a number of frames being dropped, these
patches do remedy the problem. Thanks!
--Justin Johnson


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