Unable to get 50Hz PAL-I TV-OUT

[rob_mpc]

I've been bashing my head for a week or so now trying to get a 50Hz PAL-I output from my 6150 integrated GPU.

I've tried using custom modelines in my xorg.conf, though they all seem to have been silently rejected (I saw on another thread here a comment that custom modelines are ignored in TV-OUT) and I've tried setting the "VertRefresh" option in my "Monitor" section and setting the "IgnoreEdidFreqs" option in the "Display" section, but all to no avail.

The only modes I am able to get are all at 60Hz, and some modes that the driver states should be valid (e.g. 640x400) get rejected, so ... is it me? Have I not got my xorg.conf set up correctly? Or is the NVIDIA driver unable to drive a 50Hz output for a PAL-I signal (a standard which, in the UK at least, is specified to have a 50Hz vertical refresh period).

Logs and stuff are attached...

Thanks in advance for any light you can throw on this for me...

[netllama]

How are you determining that you're getting non-50Hz refresh rates?
Does this problem persist in the 1.0-9626 driver as well?

Thanks,
Lonni

[Thunderbird]

The refresh rates values you enter aren't directly used by the tvout encoder. The encoder is really programmed to PAL-I and in general it only supports a fixed number of modes which the driver can program.

[rob_mpc]

netllama - I determine that the output is not 50Hz from:
1) the output of xrandr shows that only 60Hz refresh rates are available
2) the output from nvidia-settings (when reporting) shows a 60Hz refresh rate
3) video artifacts on screen in things like news tickers etc. that should scroll smoothly but actually have jerks every couple of frames that indicate the TV refresh and the transmitted video refresh are not the same.

I shall give the 1.0-9626 driver a go and see what happens with that...

[Thunderbird]

In case the tv only supports 50Hz and 60Hz is transmitted you will only see garbage. You won't see a constant image, all lines will be moving.

[rob_mpc]

Thunderbird - the TV supports both 50Hz (PAL) and 60Hz (NTSC) signals. My issue is not that the TV does not sync to the video, but that the video quality is not optimal due to not being played at the correct frequency.

netllama - I have tried the 1.0-9625 version of the driver (most up-to-date I could find) and this does give 50Hz output (reported through xrandr and nvidia-settings -q) so this solves part of my problem, thanks!

The issue with jerky playback of scrolling video (e.g. news tickers) seems to be an interlacing issue - changing the deinterlace filter I use to the bob filter has improved video quality in this respect greatly (as well as dramatically increasing my CPU load...)

So the next question is: Since my GPU is capable of interlaced TV-OUT (as reported in a verbose Xorg.0.log), is there any way of forcing an interlaced output from my xorg.conf? I am assuming when I ask this that a custom modeline would be rejected due to TV-0 being the display device?

Thanks for all the help so far!

[pe1chl]

You are hitting the usual issues with tv-out that have already been discussed several times....
Putting a moving TV picture into a framebuffer at some "PC standard" resolution, then scaling it to TV resolution and outputting it in an interlaced format is guaranteed to cause problems. Yet it is the base of almost any PC video card with TV-out.

[micheles]

Hi,

I wonder if you went to the bottom of this problem.
I am using mythtv with GeForce 6150 and I see exactly the same problem, that is:
- video has some artifacts on news tickers or fast moving picture (e.g. sport)
- activating bob deinterlacing fixes the problem, but it shows flickering OSD in mythtv

Even though the nvidia-settings says that refresh rate is 60Hz, I think it is really 50Hz (checked with old TV not support NTSC). So I don't think it is a refresh rate issue.
Also mplayer and xine exibits the same behaviour.
Any idea ?

[Thunderbird]

The flickering is normal. It is for a part due to the low refresh rate but for the biggest part due to interlacing (e.g. frame 1 showing only odd lines, the second showing the even lines; this causes the odd lines to be a little vague when the even ones are rendered) That deinterlacing option only affects the video itself.

[micheles]

Originally Posted by Thunderbird

The flickering is normal. It is for a part due to the low refresh rate but for the biggest part due to interlacing (e.g. frame 1 showing only odd lines, the second showing the even lines; this causes the odd lines to be a little vague when the even ones are rendered) That deinterlacing option only affects the video itself.

Hi,

I understand the way PAL works and as such you could have flickering problems. What is not clear to me is:
1) Why decoding DVB PAL video and sending it to the video card makes prints that scroll horizontally almost unreadable (these are readable using a free to air set top box or analog terrestrial PAL TV of the same channel) ?
2) Why applying a software deinterlacing to the same video, before sending to the card fixes the problem (at the end of the day is always shown in PAL interlaced way) ?

Cheers

Michele

[pe1chl]

I advise you to read about interlacing, de-interlacing and the issues surrounding it.
Horizontally scrolling text becoming unreadable is a perfectly normal artifact of improper de-interlacing, that you don't see when playing the same content on a 50Hz interlaced TV (without 100Hz technology or similar).
It is a shame that the only way to have video-out on a PC seems to be to first de-interlace to a noninterlaced framebuffer, then interlace again to a TV-out format, even without proper synchronization.
This is what causes most of the messup. That was true a year ago (when this thread was started), and it still is.