Setting maximum HDMI output framerate

[greenwal]

Thank you for xbian, it is an amazing piece of software... I have it running sweetly, but with one catch. Due to the layout of my house, the HDMI cable is quite long, and suffers from interference, but only when the framerate is 50Hz or higher.

I am familiar with setting hdmi_modes in the config.txt. If I use auto, the Pi output is always 50Hz (as the TV correctly reports it supports it) but that is flaky.
If I set config.txt to force a 24hz mode, then films run fine (as they are 24hz), but TV shows suffer horribly as they are 25Hz (or other). Switching causes the opposite problem.

Is there a way I can ask xbian (or the Pi), "use auto framerate, but only 30Hz or lower"? I suspect I must edit my own EDID file, but that looks like a rocky road...

Thank you!

Software
XBian version: 1.0 Beta 1.1
Overclock settings: None
Hardware
RPi model (model B 512mb):
SD card size and make/type: 16gig class 10
Network (wireless or LAN): Either
Connected devices (TV, USB, network storage, etc.): Panasonic Viera

[IriDium]

I guess you have read HDMI codes

I know they are a bit expensive but have you thought of a HDMI extender?

I believe 30m is possible for 1080p - your TV can't be that far away

I've never used one but maybe someone else can comment on their effectiveness.

[rikardo1979]

yes, the best way to run the HDMI for long distance would be an CAT5 cable. SO there are like an extenders and they use CAT5 cable so this can run through your house no matter how long. The cost should not be sky high and I think you can get it at decent price and it would be the best option for you or anyone who needs to get HDMI to distance longer than 2-3 meters whats I would say is the max for HDMI cable

[greenwal]

Thank you both for such quick replies! I will definitely give the cable extender a crack. I've found a Neet make on Amazon for about £30.

I did succeed in the end in forcing a specific range of HDMI modes on the Pi by exporting the edid.dat and editing it in Lightware Edid Editor. That completely prevents the flickering (by keeping the fps below 50fps), but the TV won't support 25fps, so it jerks sightly every second playing 25fps video at 24fps.

I may be overthinking this - will see what the extender does. Thank you both again...

[IriDium]

If it works - can you report back and let other users experience from your problem. Many thanks.

[greenwal]

OK, after some more experiments here's the writeup:

My TV is 15m from my amp (and pi), so I used a neet extender to run the video HDMI signal over two ethernet cables from amp to TV. But... at framerates over 30fps, the video glitched and flickered off and on. Forcing 25fps ultimately didn't work as the TV refused to support it.

So, I decided to reverse the system. I moved the pi under the TV, and ran the audio from the TV back to the amp with a 15m optical cable. That flat didn't work (it was a cheap plastic optical cable, not glass fibre, so the light became a little dim), so I replaced it with a digital coax (converting the optical signal to coax at the back of the TV using a £10 converter). Bingo!

Best part of the new system is I also get my non xbian video (standard over-air signals) going through the amp too.

Thanks again for your help!