[mythtv-users] trouble with nvidia and bob x2 deinterlacing

[Inor Kuo]

>> I have searched for and read every thread I could find on bob deinterlacing
>> but I am still experiencing significant shaking or jitter when using bob x2
>> with sd and hd recordings (NTSC). Originally I was using a modeline I found
>> in the mythtv wiki for my tv and the refresh rate came out to just under 60
>> so myth wouldn't use bob x2. In my reading I had come across threads where
>> people suggested using xvidtune to adjust the modeline so that the refresh
>> rate was just over 60.
>>
>> Modeline from wiki "1368x768 at 85" 85.50 1368 1414 1526 1798 768 771
>> 777 795 +hsync –vsync
>>
>> Modeline tweaked "1368x768 at 85" 85.50 1368 1400 1720 1792 768 783 791
>> 795 +hsync –vsync
>>
>> Xvidtune wouldn't let me adjust on the fly so I used a modeline calculator
>> http://xtimingsourceforge.net/cgi-bin/xtiming.pl and put in
>> my tv's specs and made adjustments until the refresh rate was over 60.
>> after a reboot with my tweaked modeline in xorg.conf, xvid showed the
>> following.
>>
>> Pixel Clock: 85.50 MHz
>> Horizontal Sync: 47.71 kHz
>> Vertical Sync: 60.02 Hz
>>
>> My tv is a Vizio 50" Plasma that I got from Costco about almost 2 years ago.
>> The specs from the manual are as follows.
>>
>> Resolution Refresh (Hz) H.Freq (kHz) V.Freq (Hz) H.Sync V.Sync Pixel Freq (MHz)
>> 1366x768  60               47.7             60.00          P         N         85.500
>>
>> At this point, myth let me use bob x2 but like another user reported here
>> http://www.gossamer-threads.com/lists/mythtv/users/310039?do=post_view_threaded#310039,
>> it looked like there was an earthquake going on, moreso for sd than hd
>> recordings.
>>
>> I am running mythtv version 0.21 compiled from source on Ubuntu 7.10 Gutsy
>> with an onboard Nvidia GeForce 6150 gpu using nvidia driver version 169.12,
>> 1gb of ram, 2gb of swap, and an Amd Athlon 64 X2 Dual Core 4200+ processor.
>> The plasma tv is connected to the computer via vga.
>>
>> Nvidia settings
>> 0/OpenGLImageSettings=1
>> 0/XVideoTextureSyncToVBlank=1
>> 0/XVideoBlitterSyncToVBlank=1
>> 0/XVideoSyncToDisplay=1
>>
>> In mythfrontend, I have "enable OpenGL vertical sync for timing" checked.
>>
>> I have a total of 3 combined frontend backend machines and I tried getting
>> bob x2 to work on the other two as well with the same shaky results.
>>
>>             Monitor                                GPU Nvidia          Driver Version     Processor
>> Setup 1 50"P50HDTV Vizio Plasma onboard nvidia 6150 169.12 AMD64X2 DC 4200+2.2ghz
>>
>> Setup 2 42"GV42L Vizio LCD TV     onboard nvidia 6150 1.0.9639 AMD64X2 DC 3800+2.0ghz
>>
>> Setup 3 19"Samsung 920NW LCD nvidia geforce 7300LE 100.14.19 Intel C2D 6420 2.13ghz
>>
>> On all 3 machines I had to adjust the modelines to get the refresh rate
>> above 60 using the native resolutions of the screens (although 1368x768 was
>> the closest I could get to 1366x768 for the 2 vizio's).
>>
>> I've read that there is some jitter to be expected with bob x2 enabled but
>> what I am seeing is unwatchable for sd recordings. It's better on hd
>> recordings but it gives you a headache after a while.
>>
>> I would really like to get bob working correctly but I am fairly new to all
>> of this deinterlacing and refresh rate stuff. I feel that I have done as
>> much as I can on my own and at this point I don't know what else to do so
>> I'm turning to the community for help. If anyone can offer any suggestions
>> it would be greatly appreciated.
>
>
>
> Inor,
>
> You're probably on the right track... I suggest you take one box and
> do a scientific approach only changing one setting at a time.
>
> First of all you need to get some debugging going however:
>
> mythfrontend -v playback>/tmp/frontendlog 2>&1
>
> should provide you with some nice logs.
>
> Check that you are indeed using bob deinterlace (it'll say so in the
> logs). That myth has recognized the refresh rate correctly etc...
>
> My personal idea is that you might need to turn off "enable OpenGL
> vertical sync for timing" .
>
> Cheers
>
> Steve


Thanks for the advice.  I disabled the option for "opengl vertical sync for timing" and ran mythfrontend as you suggested.  i played an hd recording for a while and then an sd recording.  i will attach the two log files in separate emails because the server rejected my first attempt due to size.  It does indeed use bob deinterlacing.  Before i adjusted my modeline, it would tell me that my refresh rate was too low and drop back to using kernel deinterlacing which is set as my fallback deinterlacer.  

One thing to note is that when i generated the log file, i did it from work via vnc.  the video/audio sync messages seem to happen only while i am remotely connected via vnc so as soon as i hit play, i killed my vnc session, and after a few minutes, logged back on to stop playback.  when i ran mythfrontend -v playback from home, i don't remember seeing any of the video/audio sync messages.

I've read that a mismatched refresh rate between the tv and what the computer puts out can cause jittering.  I can try adjusting my modeline but i don't know what to change because the one i am using now is as close to 60Hz as i could get.  Maybe i am focusing on the wrong number though.
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