[mythtvnz] 720p 30fps playback

[Stephen Worthington]

On Tue, 20 Sep 2011 20:53:35 +1200, you wrote:

>On 20/09/11 19:33, Stephen Worthington wrote:
>> On Tue, 20 Sep 2011 17:51:27 +1200, you wrote:
>>
>>> Anybody got smooth playback at the correct speed working for 720p 30fps
>>> video in mythvideo? I get rough and double-speed playback and found this
>>> in mythfrontend.log: "Video sync method can't support double framerate
>>> (refresh rate too low for bob deint)". Not sure why myth is trying to
>>> deinterlace progressive video anyway.
>>
>> What is your video card?  Some cards only support certain combinations
>> of frame rate and frame size.
>>
>> Have you checked using MediaInfo to make sure that your file is
>> actually 720p?
>>
>> Have a look at this page for how to set up Mythfrontend to change the
>> output format to match the video it is playing:
>>
>> http://www.avenard.org/media/Patches_%26_Add-Ons/Entries/2010/6/7_Matching_refresh_rate_with_input_framerate_to_reduce_judder_%3B_final_part.html
>>
>Thanks for the feedback Stephen. I have an Asus EN9400GT Silent. I think 
>it should do 60 Hz. I found a similar (identical?) web page 
>(http://www.mythtv.org/wiki/User_Manual:JudderFree) to the avenard one 
>and I did have a bit of play but no joy so far.
>
>Pretty sure my TV (Pana Plasma) will do 60 Hz but need to check this and 
>then xorg config and then yada yada .... Sigh. I banged my head against 
>refresh rates a couple of years ago when I first set up MediaPortal on 
>Vista (cringe).
>
>Certain the video is 30fps or probably 29.xx Hz NTSC. It's from my camera.
>
>Haven't got MediaInfo but ffmpeg say 30fps.

Yes, plasma TVs seem to be much less flexible about what they can cope
with.  My Sony LCD TV (KDL-35V5500) copes with most refresh rates,
although its native mode is 60 Hz, according to its EDID data.  One of
the reasons I chose it was for that ability.  I am sometimes surprised
when playing a video file to have it pop up a little 1080p/24 message
window, but since I got this TV and set up the refresh rate changing
as per that page, I have never had any judder again.  My video card is
an Asus Bravo 220 silent one, rather more modern than yours, so it
does all the available modes and the best hardware deinterlace, which
may also account for lack of judder.

I just tried playing an NTSC 720p file on my setup (29.970 Hz), and it
looks as though Mythfrontend decided that the best playing mode was
actually 1080p, and used that.  Mythfrontend reported it used
1920x1080 @ 0 Hz, which I presume meant default = 60 Hz (or actually
59.94 Hz) was used as that is the native mode of the TV and the TV
reported it was in 1080p mode.  The Nvidia 220 GPU had no problem with
upscaling and produced a superb picture.

Unfortunately, the 9400 GT is not so capable (or the Nvidia Linux
drivers for it are not so capable).  Have a look here:

/usr/share/doc/nvidia-current/html/supportedchips.html

and you will find that the 220 GPU is listed as having feature set C,
which allows it to do what is needed.  The 9400 GT is listed as having
the much more restricted feature set A.  My old 8400GS that I used
before the 220 was also feature set A and no matter what settings I
tried always had judder problems on some files, including 1080i TV
recordings.

There should be a table in the html files in that directory that lists
what each feature set does, but I can not find it at the moment.