[mythtv-users] Summery of my problems

Dylan R. Semler dsemler at macalester.edu
Sat Jan 28 17:20:24 UTC 2006



Robert Johnston wrote:

>On 1/26/06, Dylan R. Semler <dsemler at macalester.edu> wrote:
>  
>
>>I've only really been working with LiveTV so far.  HD is able to stream
>>pretty well to the frontend, but there are some problems.  In the first
>>minute or so after I change a channel, there are a few pauses but
>>eventually it smooths out (something I can live with).  However,
>>whenever there is fast motion in the video, every other line gets
>>slightly offset--I guess this is described as "combing."  How do I fix this?
>>    
>>
>
>Enable "DeInterlacing". The "Combing" is your (Progressive) laptop
>display trying to show an interlaced signal. DeInterlacing corrects
>this.
>  
>
This did the trick

>  
>
>>For analog, the picture quality is pretty bad (noisy) and there are
>>about three or four horizontal lines at the top of the screen that have
>>some random patterns of black and white streaks.  The picture quality is
>>much better using tvtime and those lines do not appear.
>>    
>>
>
>Those lines are called the "VBI" (Vertical Blank Interrupt). They're
>what gets sent as the TV's scanning electron beam travels from
>bottom-right to top-left to start the next screenful. The "Random
>Patterns" you see are (Most likely) the Timecode, and the Closed
>Captioning data. You can adjust the "Overscan" parameters in Myth to
>remove these.
>  
>
Adjusting the overscan in myth turned out to be less than ideal.  First 
of all, the adjustments apply to both the HD and the analog feeds so if 
I make adjustments that remove the black vbi lines on the top in analog 
I have to live with a few unchanging colored lines at the bottom of 
HD--very annoying.  Furthermore, my vertical over/underscan percentage 
would ideally be less than 1 (to cleanly remove all of the vbi lines and 
nothing more), but myth only seems to allow integers for this field.  
When this is set to 1 there are a few colored lines at the bottom of the 
picture similar to what is seen in HD.  Also, I found changing the 'Scan 
displacement (Y)' didn't seem to do anything.

>As for the noise, make sure that Myth is tuning into the same
>frequency (EXACTLY the same frequency) as TVTime is. It sounds like
>Myth's off by a few Khz.
>
>  
>
>> Also, the color
>>balance is not quite right, but when I press F to 'rotate between
>>Picture Adjustments (Colour, Hue, etc.)', nothing happens.  If I press
>>'G', I am able to make the adjustments for the recording.  Also, the
>>backend logs indicate that its using v4l v1 rather than v4l v2:
>>    
>>
>
>IIRC, ATI cards don't support the XV picture controls. This is a
>problem with their drivers.
>
>  
>
Not surprising, however, if I run the frontend on the master backend 
with the GeForce2 as well as another frontend with a GeForce4 and still, 
I have the same result; pressing 'f' in livetv does nothing.

>>>Channel(/dev/video0)::SwitchToInput(in 0): Error -1 while setting
>>>video mode (v2), "Invalid argument", trying v4l v1
>>>2006-01-26 22:52:21.234 Channel(/dev/video0)::SwitchToInput(in 0):
>>>Setting video mode with v4l version 1 worked
>>>      
>>>
>
>Check the drivers you are using.
>
>  
>
>>Non-mythtv issue but maybe someone has a clue.  The master backend does
>>not draw the desktop onto the entire monitor or tv (when using s-video
>>out).  There is a black bar on the left side where the monitor and tv
>>are scanning, but nothing is drawn (does that make any sense?).  I am
>>currently running without any nvidia drivers, but the problem exists
>>with a driver installed as well.  Any ideas?
>>    
>>
>
>Make sure you are using the NVidia driver (Just having it installed
>does no good, it needs to be defined in your
>Xorg.conf/XFree86Settings-4 file). Also check your ModeLines to make
>sure you're using a proper modeline for your display (And make sure
>you have the correct type of TV-Out defined. Outputting a PAL picture
>to an NTSC TV will give black borders, as the picture sizes are
>different).
>  
>
I installed the nvidia driver and made the adjustments to xorg.conf, 
which seems to have helped for the monitor.  However, tv out still is 
not perfect.  I set tv-out standard to NTSC in xorg.conf (which is the 
default anyways), however it does not fill the entire screen.  I'm 
pretty sure this TV was bought in the US but maybe I'll play with the 
other format options and see if I get lucky.

Other things I forgot to bring up.  My laptop has a widescreen display 
(16:10) and analog displays in full screen (i.e. stretched.)  Is it 
possible to have it displayed at the correct aspect ratio with black 
bars on the sides?


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