[lug] TV-out on a NTSC CRT TV

Lee Woodworth blug-mail at duboulder.com
Wed Dec 29 23:36:56 MST 2010


On 12/29/10 20:56, Davide Del Vento wrote:
>> If you just need to display the video in a larger size and the laptop
>> has an external VGA connector, you could use a data projector. You can
>> bypass the TV stuff that way. Just be sure to set the VGA output's
>> timing and resolution to something the projector can handle,
>> e.g. 1024x768 @ 60Hz.
> 
> Sure, this would be great, but I need a projector which I don't have
> and I don't have the budget for (well, let's say I could invest up to
> $50 in it, but I don't think it's a reasonable budget for even a
> crappy VGA projector - I saw a S-video projector on woot.com days ago
> at $25, but that might not have solved the problem).
> Then, with a projector, I'd likely encounter other issues, such a
> strong keystone, since the location of the room is always weird...

Don't know if borrowing one from work would be possible or worthwhile....

> 
>> Otherwise, have you tried (for xrandr version 1.3)
>>    xrandr --verbose --prop
>> to see what resolutions and timings the X server thinks the
>> hardware supports?
> 
> I did (see attachment). I learnt that it does use ntsc, so that part is fine.
> 
>> Have you looked at the X server logs and xsession logs to see
>> what the video driver reports it is doing?
> 
> I did after your suggestion, and I think you nailed it. It's full of errors like
> 
> (doublescan mode not supported)
> (vrefresh out of range)

This is the driver deciding that certain display resolutions require timing
the output/display device doesn't support.

> 
> for dozens, probably hundreds of different resolutions (I copied just
> the last ones, right before some other interesting messages).
> Unfortunately, I can only guess what that mean, Google doesn't help,
> and I have no idea if it's fixable and if yes, how.
> 
> Additional thoughts?

NTSC has 525 scan lines total (including vertical retrace), with approximately
480+/- visible. This looks to match the 640x480x60Hz setting in your log.
Your graphics driver is defaulting to 800x600 which could be a good match
for PAL. The higher resolution is probably why the output you do see
is too small.

So this is what I would try:

1) Set the S-video output resolution for NTSC instead of PAL:
       xrandr --output S-video --mode 640x480 --rate 60
   You might need to use an XID for the mode if there is more than
   one labeled 640x480 by xrandr: in that case use --mode 0x59
   (which comes from your xrandr output).

2) turn off the LCD panel if possible using the Fn keys, or
   try xrandr --output VGA-0 --off

3) adjust the TV sync/roll settings to get a stable picture.

If that doesn't work, try setting VGA-0 to 640x480 also. Make sure
to move desktop items in from the edges in the high res mode before
you switch to low res, otherwise you might not be able to get to them.
It depends on whether the WM redoes the layout after a resolution change.

   xrandr --output VGA-0 --mode 640x480 --rate 60

HTH

> 
> Thanks,
> Dav
> 
> 
> 
>>
>>>
>>> Thanks,
>>> Davide
>>>
>>> On Mon, Dec 27, 2010 at 12:07, Davide Del Vento
>>> <davide.del.vento at gmail.com> wrote:
>>>> The machine is running Ubuntu 8.04 and that doesn't show anything on the TV.
>>>> I tried a couple of distro I had on live CD and the one those worked (sort
>>>> of). It is Ubuntu 10.04 but is not prompting me for any proprietary driver.
>>>>
>>>> I thought that since I was seeing *something* (and I don't care about the
>>>> resolution, 320x200 would be ok for me :-) this was something more about the
>>>> TV than about the video card. Since it is a very old laptop (at least 5
>>>> years, probably 10), I have no idea about what hw is inside, beside the
>>>> disk, which I replaced myself. I know is an HP, only because the logo is
>>>> very noticeable :-)
>>>> Anyway tonight I'll check the make/model of the video section (and I'll
>>>> Google possible solutions before bothering you).
>>>>
>>>> Thanks for the advice,
>>>> ;Dav
>>>>
>>>>
>>>> On Sun, Dec 26, 2010 at 21:48, John Hernandez <jph at jph.net> wrote:
>>>>>
>>>>> Hi Davide, it would help to know more specifics about the video
>>>>> hardware (lspci output) and the Linux distro/version.
>>>>>
>>>>> This may be dated information, but I think the proprietary driver was
>>>>> the fastest (perhaps only?) path to TV-out success with nVidia
>>>>> systems.  I don't recall ever doing that with older ATI or Intel
>>>>> hardware, but I bet someone here did...
>>>>>
>>>>> On Sun, Dec 26, 2010 at 11:23 AM, Davide Del Vento
>>>>> <davide.del.vento at gmail.com> wrote:
>>>>>> Hi,
>>>>>> I'm trying to have a TV (not-too-old, but CRT) working with the TV-out
>>>>>> of my media laptop (a very old HP bought in Italy). Purpose: show the
>>>>>> kids some cartoons on a larger screen.
>>>>>>
>>>>>> I'm struggling to have it working: I do see the image, but it is never
>>>>>> good enough. The autodetected default call the "monitor" unknown, and
>>>>>> use an non-interlaced mode which shows double images, partially
>>>>>> overlapping in vertical, and some flickering.
>>>>>>
>>>>>> I tried these:
>>>>>> http://www.arachnoid.com/modelines/
>>>>>>
>>>>>> http://www.mythtv.org/wiki/Modeline_Database#NTSC525_itu-r.2Fbt:_470_601_656
>>>>>> http://smackmini.dax.nu/tv-out.html (I know, this is PAL)
>>>>>>
>>>>>> without any success, besides understanding what follows:
>>>>>>
>>>>>> 1) I figured out that using an interlaced mode, stops the flicker and
>>>>>> completely separates the images, so I can see two images (squeezed in
>>>>>> the vertical direction), one on top of the other - with a relatively
>>>>>> large black area in between (and probably part of the images out of
>>>>>> the screen). From here, I tried to play with the other numbers, to see
>>>>>> if I could move one image out of the screen and enlarge the other one,
>>>>>> but...
>>>>>>
>>>>>> 2) the other numbers of the modelines, don't seem to have any
>>>>>> noticeable effect, maybe the TV is "autocorrecting" whatever it is
>>>>>> receiving to what it thinks is the right way?
>>>>>>
>>>>>> Any suggestion on what to do?
>>>>>>
>>>>>> Thanks,
>>>>>> Davide
>>>>>> _______________________________________________
>>>>>> Web Page:  http://lug.boulder.co.us
>>>>>> Mailing List: http://lists.lug.boulder.co.us/mailman/listinfo/lug
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>>>>>>
>>>>> _______________________________________________
>>>>> Web Page:  http://lug.boulder.co.us
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>>>>
>>>>
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>>
>> _______________________________________________
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>>
>>
>>
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