[Live][Windows] HTPC on Revo 3610 via HDMI A/V receiver timings issue and resolution
#1
Thumbs Up 
Hi All,

I had an issue with the video resolution and timings when running XBMC (or any program, really) through my receiver via HDMI and have found a resolution that worked in my case. Initially when I had the problem I searched the web to no avail but noticed some other people had been asking about the same issue but never had any answers. I had the intention of creating a post like this back when I found a resolution but life got in the way and I ended up forgetting about it. Recently I switched from XBMC under Windows to XBMC Live and the same problem crept up so here I am offering solutions for both Windows and Live/Ubuntu for an issue that I don't believe is very common. Please note that this is not XBMC specific but there are a lot of posts here dealing with screen resolutions and timings so I thought it would be a good place to start. Also, when searching for resolutions about these types of issues this forum always shows up at the top of the results. So, here we go!

Problem:
Connecting my HTPC (XBMC, of course) to my LG projector via HDMI causes timing issues when routed through my Pioneer A/V receiver. My projector supports 1080p and I can use 1920x1080x(24/50Hz) but when I choose 1920x1080x60Hz I get a timing issue where the display is out of sync (picture keeps rolling) and is obviously not viewable. Lower resolutions at 60Hz work fine. If I bypass the receiver the problem totally goes away.

Equipment:
Acer Revo 3610 PC
Pioneer 1018AH A/V receiver
LG CF181D projector

[Windows] Resolution (for nVidia cards):
What worked for me was creating a custom resolution in the nVidia Control Panel and selecting the appropriate timings (was guesswork). You do so by opening the nVidia Control Panel and navigating to the Change Resolution section and at the bottom is a button labeled "Customize...". Click that button to open up the Customize settings. This allows you to create a custom resolution that you can then set for your display. Please heed the warning that setting your display to incorrect timings can ruin your display. Under these settings I set the resolution to 1920x1080, 60Hz refresh rate, and Progressive scan type. There is a down-arrow Timing button that when clicked reveals the Standard timing choices. It is in there where I found the fix. For my particular case, choosing the DMT timing standard fixed my issue. I basically went down the list, chose the next timing standard, then clicked the Test button to try it out until I found one that worked. I simply set that resolution and never looked back... until...

[Live] Resolution:
When I recently moved from XBMC Windows to Live this issue crept up again and unfortunately I'm not nearly as sufficient in Linux than I am in Windows so it took quite a bit to resolve the issue. Again, when running through the receiver I had exactly the same problem at 1920x1080x60Hz. Searching around the web I found this post on here: http://forum.xbmc.org/showthread.php?tid=54685

It was that post that helped me get going so thank you, The-Boxhead!!

Anyway, it had been a while since I resolved the issue in Windows so I didn't remember what timing standard had fixed my issue and at this point I didn't even realize that it is, in fact, a standard and had assumed the fix in Windows was specific to my display. (Note that when connecting through the receiver Windows/Linux sees the display as the receiver and not the projector, but that didn't matter even when forcing EDID information as the projector). So, not remembering which timing standard I tried both GTF and CVT first since there are utilities available in the Live version of Ubuntu. The utilities are: cvt and gtf. You basically run those programs giving the desired resolution and refresh rate and it spits out the Modeline you need to add to the xorg.conf file. Neither of those were working for me and I still had a feeling it was the DMT timing standard but I couldn't find a utility to calculate those timings. That is, until I realized the nVidia Control Panel gives the required settings! I fired it up on my Windows 7 machine, also using a nVidia card, and selected my desired resolution and there were the golden numbers that I needed. You need to do a little simple math to transfer the numbers to what Modeline needs but they are all there.

Modeline parameters are as follows:
ModeLine "<ModeName>" <PixelClock> <HRes> <HSyncStart> <HSyncEnd> <HTotal> <VRes> <VSyncStart> <VSyncEnd> <VTotal> <HPolarity> <VPolarity>

nVidia Control Panel gives you these numbers as follows (for both Horizontal and Vertical):
Active Pixels, Front Porch (pixels), Sync width (pixels), Total pixels.

To calculate the appropriate values for Modeline, use the following:
PixelClock = Pixel clock (shown in bottom-right, currently)
[H/V]Res = [Horizontal/Vertical] Active Pixels
[H/V]SyncStart = [Horizontal/Vertical] Active Pixels + [Horizontal/Vertical] Front Porch (pixels)
[H/V]SyncEnd = [Horizontal/Vertical] Active Pixels + [Horizontal/Vertical] Front Porch (pixels) + [Horizontal/Vertical] Sync width (pixels)
[H/V]Total = [Horizontal/Vertical] Total pixels
[H/V]Polarity = [Horizontal/Vertical] Polarity

Using this method I could calculate the exact timings for each of the standard timing modes and finally my issue was resolved by using the DMT settings. I am assuming this will also work for non-nVidia cards as it should not be card-specific but you would need access to the nVidia Control Panel as it does the correct calculations. I did notice that when checking the results from both the cvt and gtf programs that the Pixel Clock value was rounded by them but nVidia Control Panel goes out to 4 decimal places. In my Modeline I used the nVidia value -- I don't know if it makes a difference but figured it couldn't hurt to be more specific. Also, I don't think these calculations are widely available as the documentation for the cvt/gtf notes that they are not easy to come by but using the nVidia Control Panel should give everything that is needed.

Finally, I am assuming the root of the problem is that my receiver is not truly HDMI passthrough as it is supposed to be and it is somehow causing the timing issue because when I bypass it, I don't have this problem at all. In Linux, when I created the log from X (as described in the post I linked above), I did so when routing HDMI through my receiver and also directly to the projector. Both logs showed the same capabilities which are those of the projector (although when routed through the receiver I do see the receiver manufacturer information instead of the projector) so it does appear the receiver is passing through HDMI correctly but I still believe it is somehow messing up the timings at 1920x1080x60Hz.

Sorry for the long-winded post but I really wanted to get this documented so that it may help others out there.
Reply

Logout Mark Read Team Forum Stats Members Help
[Live][Windows] HTPC on Revo 3610 via HDMI A/V receiver timings issue and resolution0