Using RTC for video timing

[cabbage]

Dear all,

I'm getting intermittent tearing on playback which I'm putting down to video timing issues as described here:

http://www.mythtv.org/wiki/Frame_display_timing

I'm running mythbuntu 9.04 with 0.21-fixes.

I'd like to get the RTC timing option working but I'm getting a permissions error:

RTCVideoSync: Could not open /dev/rtc, Permission denied.

Now /dev/rtc links to /dev/rtc0 which has owner and group of root 770.

So how do I change the group on /dev/rtc0 to include mythtv?


Thanks,

Cabbage.

[cabbage]

OK... Thanks to inspiration from this thread:

http://ubuntuforums.org/showthread.php?t=168221

I've created a udev rule to modify the group permission on the rtc0 device:

KERNEL=="rtc0", ATTR{name}=="rtc_cmos", GROUP="mythtv"

This works... but now I get the following error from mythfrontend:

RTCVideoSync: Could not set RTC frequency, Permission denied.


I've already modified sysctl.conf and set:

dev.hpet.max-user-freq = 1024

What else do I need to do?

[xinix]

I'm not sure I can see a difference while using RTC. But I did get past this error. RTCVideoSync: Could not open /dev/rtc, Permission denied

I did this by changing the permissions for /dev/rtc0 so that all users have access to it. Not a pretty fix but it does give the results you want.

Use this command, as sudo/root, to do it manually:
chmod 666 /dev/rtc0

After doing this you will see something like this in your mythfrontend log:
2009-10-25 22:32:28.893 Video timing method: RTC