CRT jack quality


21 posts
by triggerhurt » Tue May 22, 2012 7:39 pm
Is the video quality of the raspi as good as a "oldschool" dvdplayer? There are only little pictures in the webz and they do not really tell the whole story... Somebody using xbmc and an old crt tv? How is the quality?

Best regards

trigger
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by arm2 » Tue May 22, 2012 8:28 pm
The only way you will get a signal into most CRT TVs would be Composite Video probably into a SCART socket. Whilst DVD players will also use a SCART socket they will normally using the RGB pins which gives a better quality. I'd expect something slightly better than playing a professionally recorded VHS Video. But a movie (a constantly moving image) will look better than a static computer text or desktop images.
Bottom line don't expect much, but a phono to scart lead should be cheap so its worth a try.
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by lewmur » Tue May 22, 2012 9:38 pm
triggerhurt wrote:Is the video quality of the raspi as good as a "oldschool" dvdplayer? There are only little pictures in the webz and they do not really tell the whole story... Somebody using xbmc and an old crt tv? How is the quality?

Best regards

trigger

Drop the resolution on your computer to 600 x 400 and check out the text. That is still better than composite video. Even interlaced standard TV is only 512 scan lines.
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by triggerhurt » Wed May 23, 2012 6:00 am
Thanks for the answers so far but probably I should have been more precise. I already know all I need to connect the raspi (when it arrives some day) to my crt TV. I even bought the needed adapters long time ago (my tv only allows scart). Question is however is the raspi providing a high quality picture through the video jack (of course one cannot compare it to digital standards)? I'm askin because I had a VGA to Video Jack converter several weeks ago and the video quality was quite bad and not in one world with our normal dvd player :|

I did not see any complaints so it should provide a quite decent quality for an analogue signal shouldn't it?
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by Robert_M » Thu May 24, 2012 10:57 pm
I don't have XBMC running yet, but for myself I find that in terminal mode the R-Pi looks good enough on my old TV, but when I go into the LXDE the scan artifacts make it less pleasant to look at for any length of time. Which means I'm running tightVNC on the Pi and running the LXDE across the network from my WinXP computer.
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by AndrewS » Thu May 24, 2012 11:08 pm
Robert_M wrote:Which means I'm running tightVNC on the Pi and running the LXDE across the network from my WinXP computer.

No no no, you're doing it the wrong way round! :lol:
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by Robert_M » Thu May 24, 2012 11:26 pm
My Bad!

Does this mean I have to send my Pi back?
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by Robert_M » Thu May 24, 2012 11:34 pm
Oh, wait! Just Kidding!

I'll send my WinXP box back, instead! :D
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by mahjongg » Fri May 25, 2012 12:15 am
The quality of the CRT jack seems sturdy enough for me..... :twisted:
Oh, you wanted to comment on the picture quality of a TV connected through to composite video signal? :idea: , well its composite video, :| and from the pictures I have seen, for composite video it seemed reasonable to me. :roll:

Seriously, this is a very misnamed post!
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by Robert_M » Sat May 26, 2012 8:33 pm
So, today I have another (perhaps relevant?) answer to the original question about video quality of the Pi on a CRT/TV.

I just discovered the "/hello_pi/hello_video/" folder and running the demo video on the Sylvania 20" TV looks like it's running straight off a DVD player. Wow! I'm impressed! :D
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by toxibunny » Sat May 26, 2012 9:17 pm
What's it like compared to a games console? A gamecube or a PS2, say... Purely talking about the signal quality coming out of the RCA jack, remember... :)
note: I may or may not know what I'm talking about...
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by AndrewS » Sat May 26, 2012 11:00 pm
Has anyone ported a gamecube or PS2 emulator to the raspi yet? :twisted:

(deliberate misunderstanding ;) )
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by triggerhurt » Tue May 29, 2012 10:20 am
Thanks for all the answers especially the one of robert_m! Can't wait until it finally arrives here :twisted:
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by Thule » Sat Jul 21, 2012 8:49 am
I have tried the composite video on 2 CRT TVs and the image is very blurred. I cannot use the Pi with this poor picture quality.

Does anyone else have this problem?
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by dom » Sat Jul 21, 2012 9:52 am
Thule wrote:I have tried the composite video on 2 CRT TVs and the image is very blurred. I cannot use the Pi with this poor picture quality.


It's very hard to tell if your desciption of poor quality is the expected low resolution analogue quality that any composite output has, or if you have something more than that (e.g. a hardware fault).

Can you post a photo of the screen showing the problem?
Ideally also show a photo of the same screen being driven by a different composite device for comparison.
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by Thule » Sat Jul 21, 2012 9:59 am
Thanks for the response. I will have a go later. The image is blurred on both TVs. I have to squint.

I have an old CX5M MSX machine that has a composite output and I do not get that level of blurring.

Is there anything that can be done in sw?
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by portets » Sat Jul 21, 2012 10:14 am
My pi doesn't look quite as good as say, the web browser on my Wii. Slightly blurrier, increased flicker. But it certainly is clear enough to use. Especially after messing with the config file.

Hey Dom, that reminds me. The Wii has a flag for every program allowing it to reduce flicker in 480i mode. Not sure if this is your area at all, but could a software piece in the firmware be able to enable flicker reduction like the Wii? or do you think that would be a hardware thing?
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by dom » Sat Jul 21, 2012 10:25 am
portets wrote:The Wii has a flag for every program allowing it to reduce flicker in 480i mode. Not sure if this is your area at all, but could a software piece in the firmware be able to enable flicker reduction like the Wii? or do you think that would be a hardware thing?


Pretty sure flicker reduction is a top to bottom filtering of the image. Possible just halving the vertical resolution so the odd and even interlace fields are the same.
It could be done in software on the ARM, although the GPU could probably do it more cheaply.
I'll have a look, but considering the limited resolution of composite to begin with, I'm not sure this filter (that *must* reduce resolution) is going to be very useful.
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by portets » Sat Jul 21, 2012 10:39 am
That makes sense. I noticed a recent update to Netflix on the Wii turned off flicker reduction(very noticable), but I also noticed the text is now way sharper and more clear.

That said, the Wii's internet browser doesn't flicker and still has fairly clean text. If the filter was a framebuffer thing and only effected the console and X, that means all other apps like quake would be unaffected. And the flickering is only problematic where text is, like X.

I sadly only have an old 480i CRT TV. :?

edit: Just checked and pressing the Wii home button on a flicker vs non-flicker app shows the filter. On flicker, a 1 px horizontal line dances between scanlines. non-flicker takes up 2 scanlines. And I much prefer the non-flicker text. Don't know about others. Maybe the Wii gets by having reduced resolution with the filter by having sub-pixel rendering?
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by dom » Sat Jul 21, 2012 11:49 am
portets wrote:That makes sense. I noticed a recent update to Netflix on the Wii turned off flicker reduction(very noticable), but I also noticed the text is now way sharper and more clear.

That said, the Wii's internet browser doesn't flicker and still has fairly clean text. If the filter was a framebuffer thing and only effected the console and X, that means all other apps like quake would be unaffected. And the flickering is only problematic where text is, like X.

I sadly only have an old 480i CRT TV. :?

edit: Just checked and pressing the Wii home button on a flicker vs non-flicker app shows the filter. On flicker, a 1 px horizontal line dances between scanlines. non-flicker takes up 2 scanlines. And I much prefer the non-flicker text. Don't know about others. Maybe the Wii gets by having reduced resolution with the filter by having sub-pixel rendering?


Can you try:
Code: Select all
fbset -s                                                                                                             
                                                                                                                                       
mode "656x416"                                                                                                                         
    geometry 656 416 656 416 16                                                                                                         
    timings 0 0 0 0 0 0 0                                                                                                               
    rgba 5/11,6/5,5/0,0/16                                                                                                             
endmode                     

(your numbers may be different if you are using PAL or different overscan). So on mine, the height is 416. We want to change that slightly.

So add to config.txt
Code: Select all
framebuffer_height=418

That should cause a slight vertical resize, which has the side effect of lowpass filtering the display. Does it help flicker?
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by DeFrivoleFramboos » Sun Jul 29, 2012 6:45 pm
dom wrote:Can you try:
Code: Select all
fbset -s                                                                                                             
                                                                                                                                       
mode "656x416"                                                                                                                         
    geometry 656 416 656 416 16                                                                                                         
    timings 0 0 0 0 0 0 0                                                                                                               
    rgba 5/11,6/5,5/0,0/16                                                                                                             
endmode                     

(your numbers may be different if you are using PAL or different overscan). So on mine, the height is 416. We want to change that slightly.

So add to config.txt
Code: Select all
framebuffer_height=418

That should cause a slight vertical resize, which has the side effect of lowpass filtering the display. Does it help flicker?


That did help a bit, thanks!
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