LibreELEC 9.2: Pi4 picking the wrong resolution (720 instead of 1080i)

solarjoe · February 7, 2020 at 7:01 AM

I recently changed from a Pi1 with OpenELEC to a Pi4 with LibreElec 9.2.

The Pi4 does not find the best resolution offered by the Philips TV:

Code

tvservice:
HDMI0:EDID preferred mode remained as CEA (20) 1920x1080i @ 50 Hz
with pixel clock 74 MHz

Previously I was using a Pi1 with worked fine with

Code

disable_overscan=1
# 1920x1080i@50HZ
hdmi_group=1
hdmi_mode=20

If I use the same settings now on the Pi4 with

Code

hdmi_group=1
hdmi_mode=20
#in distconfig
dtoverlay=vc4-fkms-v3d
disable_overscan=0

the Pi4 shows the image in 1280x720@60Hz.

I tried

Code

hdmi_force_mode=1

but without success.

Any ideas what could be the problem?

**Da Flex** · February 7, 2020 at 10:55 AM Official Post

Looks like a problem of interlaced video modes. Has your TV the ability to display 1080p?

solarjoe · February 7, 2020 at 11:17 AM

No, don't think so.

I will look at tvservice again later, but wouldn't 1080p be the EDID preferred mode then?

The think that I can not make sense of is that it worked on the ancient Pi1 without issues.

I only saw that the current resolution is 1280x720 is nn KODI - System Information.

I there a way to use tvservice to show the exact mode currently used?

Not sure if it's 720p or 720i. Not sure if 720i exists at all.

**Da Flex** · February 7, 2020 at 11:38 AM Official Post

Quote from solarjoe

I there a way to use tvservice to show the exact mode currently used?

tvservice -s

solarjoe · February 7, 2020 at 12:19 PM

Thanks, the current mode used is

state 0xa [HDMI CUSTOM RGB lim 16:9], 1280x720 @ 60.00Hz, progressive

Code

Group CEA has 13 modes:
mode 1: 640x480 @ 60Hz 4:3, clock:25MHz progressive
mode 2: 720x480 @ 60Hz 4:3, clock:27MHz progressive
mode 3: 720x480 @ 60Hz 16:9, clock:27MHz progressive
mode 4: 1280x720 @ 60Hz 16:9, clock:74MHz progressive
mode 5: 1920x1080 @ 60Hz 16:9, clock:74MHz interlaced
mode 6: 720x480 @ 60Hz 4:3, clock:27MHz x2 interlaced
mode 7: 720x480 @ 60Hz 16:9, clock:27MHz x2 interlaced
mode 17: 720x576 @ 50Hz 4:3, clock:27MHz progressive
mode 18: 720x576 @ 50Hz 16:9, clock:27MHz progressive
mode 19: 1280x720 @ 50Hz 16:9, clock:74MHz progressive
(prefer) mode 20: 1920x1080 @ 50Hz 16:9, clock:74MHz interlaced
mode 21: 720x576 @ 50Hz 4:3, clock:27MHz x2 interlaced
mode 22: 720x576 @ 50Hz 16:9, clock:27MHz x2 interlaced

Display More

So no 1080p.

**chewitt** · February 7, 2020 at 12:32 PM Official Post

Kodi outputs progressive and interlaced media output is faked, e.g. 1080i@25 (typical PAL content) will be output as 1080p@50 (one interlaced frame per refresh, so double the number of interlaced frames). This means even if it can see 1080i in the list, it will choose 720p as the desktop resolution. I forget how things have evolved over Kodi releases, but IIRC this has been the behaviour for some time but older releases wrongly reported things so people believe they were using 1080i desktop in the past when they weren't.

**Da Flex** · February 7, 2020 at 12:59 PM Official Post

Then faking an interlaced mode might work (1080p at 30Hz):

Code

hdmi_group=1
hdmi_mode=34

solarjoe · February 7, 2020 at 6:58 PM

Hm, that did not work, maybe because my TV does not support 1080p@50?

The highest progressive modes are

1280x720 @ 50Hz

1280x720 @ 60Hz

**Da Flex** · February 8, 2020 at 8:41 AM Official Post

Thanks for testing. My math was that half of the progressive rate would be interpreted as interlaced rate. Unfortunately that doesn't work.

I'm running out of ideas now. As chewitt mentioned, you maybe never used an interlaced mode on your other RPi.

solarjoe · February 8, 2020 at 12:22 PM

I found that in the Kodi Forum, is it correct?

Quote

If your TV only accepts 1080i, but not 1080p, its almost certainly only HD ready, so 720p native resolution.

**Da Flex** · February 8, 2020 at 12:59 PM Official Post

It is correct, but it doesn't help. Your TV is "HD ready" standard.

According to this it's very difficult to deal with interlaced video modes. So I think Kodi has good reasons not to support interlaced modes.

Maybe you had real interlaced modes on other RPi OS'es, but on LE (and other multimedia OS'es) your chance is very low to make it work.

solarjoe · February 8, 2020 at 4:40 PM

This is the TV

widescreen flat TV 42PF9731D/10 | Philips

Panel resolution 1920 x 1080p

The previous system was no "RPi OS", it was an older version of OpenELEC with KODI 15 Isengard and it worked fine in 1080i.

**Da Flex** · February 8, 2020 at 5:27 PM Official Post

The specs say that you have 1080p, so you were not correct at post #3.

That's a game changer. It means, not all available video modes are detected by LE.

Now my suggestion is to check your HDMI cable. Try a different cable or buy a new one.

You need an HDMI 2.0 or 2.1 standard cable be future-proofed for 4K.

Don't be sure you really used 1080i on OpenELEC, because your TV has 1080p.