First post here - great forum, and knoppmyth is awesome. Plenty of info here to take me easily from random PC parts to a fully functioning PVR

I'm running w/ a 5200FX for TVOUT using an svideo->composite adapter. Everything works fine with X resolutions set to 800x600 and 640x480.

I've recently been trying to switch to 720x480 resolution all around. I finally got X to load at that resolution w/ the 5200FX after finding a working modeline.

With zero adjustment, the GUI looks perfect. No over/underscan, no offset needed, just perfect. However, video playback (Live or recorded TV) appears, at first blush, to be horizontally underscanned - I have black bars on the left and right of the video.

So I went to play w/ the tv playback over/undscan settings. Vertical over/underscan setting has an obvious effect on the video. It's, as expected, either over or underscanned. The horizontal over/underscan settings tho didn't appear to have any effect at all - adjusting this setting makes no difference in the black bars. So I cranked the horiz. overscan waaaay up, and realized that it is in fact modifying the overscan, but it's doing it within the confines of the existing video output - ie, i still have the black bars on the sides, but the video is being stretched horizontally within that output space.

I have confirmed that this also happens when playing back video from xine or mplayer. It seems any fullscreen video output is horizontally squished.

It almost looks like all the FS video playback is at 640x480 instead of 720x480, leaving me the empty space on either side of the video.

Also worth mentioning that the OSD seems to adhere to the 720x480, and looks just as I'd expect it to. It is wider than the video playback.

Any thoughts? Suggestions? Thanks much in advance!

Its most likely an aspect ratio issue: 800x600 and 640x480 are both 4:3. 720x480 would then be 3:2 (as far as mythtv is concerned), and so mythtv tries to preserve the correct aspect ratio and displays it at 640x480 as you observed. I think this can be solved by adding into your /etc/X11/XF86Config-4 in the monitor section the line:
DisplaySize 240 180
In theory this is the size of your display in mm and the fonts and aspect ratio sizes are adjusted according to this. Your numbers will vary, the point being that they should be in a 4:3 ratio. Good luck

Thanks much for the response misterflibble!

Unfortunately, no dice on fixing the video output issue.

However, it did lead me to getting the DisplaySize value set correctly to force 100dpi fonts, and suddenly my guide looks 100x better!

I followed the instructions in the following thread for properly calculating and setting DisplaySize:

http://mysettopbox.tv/phpBB2/viewtopic. ... isplaysize

I tried for both 75dpi and 100dpi, and neither had any effect whatsoever on my video playback output.

What values did you end up trying? Are they at a 4:3 ratio?

Very close, but not quite. I'm using 183 122 for 100 DPI, which actually works out to ~4.5:3.

However, I have solved the problem. I feel a bit silly as this was pretty simple.

You mentioned 4:3 aspect ratio, right? Well, on TV where pixels aren't neccesarily square, 720x480 is 4:3. With PC video output, it's not. The default playback aspect ratio was 4:3, and that's precisely how it was displaying it. Since the vertical res looked correct, I'm guessing it kept the 480, so was displaying 640 horizontally. 4:3. Duh.

So I set the default aspect ratio to Fill, and had to play a tiny bit with my overscan, and now everything is perfect.

Now to figure out how to set/change the Xine aspect ratio.

Thanks for the help!

Well I'm glad that fill worked, but as you noticed, it only works for mythtv. You ended up using a 4.5:3 ratio...which again, works out to 3:2, and so you're gonna still get it squashed in exactly the same way, because its still thinking that the pixels are square. Try something like 162 122 or 183 137. Keep in mind that these values have nothing to do with the modeline you use: they're only related to the real dimensions of your screen. These values are what xine uses to figure out how to stretch the video output and if you fix it for mythtv, it'll fix it for xine.

I'll take a stab at assuming this is the same problem I am experiencing with bttv drivers and my Osprey 100 (bt8x8) cap card.

Mythtv and bttv drivers are working great, but im seeing massive overscan outputting from the card with a video input that normally fills a 640x480 scan when using the OEM drivers under windows.

After some research, it appears that the generic/3rd party drivers are taking the raw frame data without resizing or cropping. This behavior is noticed using generic btwincap drivers in windows vs OEM drivers (such as Osprey, Hauppauge, etc).

The issue seems to be that bt8x8 chipset supports hardware cropping and scaling of the input signal, so that a "full" 640x480 frame is outputted from the driver/hardware. It appears that on the OEM drivers, they incorporate some hw cropping and scaling adjustments natively, whereas the bttv/btwincap drivers do not.

I was playing around with the advanced options of v4l2/bttv driver via v4l2-ctl utility, but it appears that the IOCTL is not supported currently in bttv (although it should, since bt8x8 hardware supports it, and it is a v4l2 spec)

Luckily it seems that somebody is already working on this and it's getting the patches merged into v4l-dvb driver code.

see this post:
http://marc.theaimsgroup.com/?l=linux-v ... 716813&w=2

This is not so much a mythtv issue, but I hope that the KnoppMyth maintainers can incorprorate such a patched driver into the next release.

Next question is, once this is implemented, how would one go about setting these up everytime myth starts to capture?

Maybe i'm braindead, but I've read myth and myth arch docs over several times, and I still dont see the EXACT path/method that they capture from the hardware/driver?

Theoretically you could use a v4l2-ctl --set-fmt-crop command?


Anyways.. maybe we can spark up some discussion on the issue - I've seen too many people notice the "black bars" on the left and right side of their bttv captures, and have people just resign them to adjusting frontend overscan/underscan settings to compensate.

This does not fix the original issue that the input video is overscanned to much to begin with. Hence this post..

Ok rant over.. now for some construction. Can anybody build those drivers and test bttv hw cropping/scaling functionality?

Thanks,
Jens