Fix HDMI monitor not working with Raspberry PI

With the increasing hardware variety of monitor / TV, using Raspberry PI with a different HDMI monitor or TV can lead to video issues from first boot. In these cases, both Raspberry PI OS Lite and Desktop distributions can suffer problems in showing their interfaces on screen, resulting in unusable video. This kind of problem doesn’t involves OS working state by itself (networking and SSH will work if configured from flashing phase and remotely accessed), but makes your device not usable from directly attached monitor. This happens also with different distributions installed on Raspberry PI.

In this tutorial I’m going to show you how to configure your Raspberry PI OS to start from first boot with a pre-defined resolution.

Before Changing Resolution: Check Hardware

Before starting with configuration files to manage and edit (as classic Linux geek habits), you need to check that available hardware is ok.

First test involves Raspberry PI + HDMI cable: if it is possible to you, connect them to a different HDMI monitor / TV (maybe from your friend, if you don’t have a second one). If this test is passed you can move on next paragraph. If this test fails, you could need to re-check:

• Operating System flashing operation
• HDMI cable quality
• Power Supply capacity (I always suggest to use at least a power supply capable to give 2,5 / 3 A, expecially if you could use your RPI also with external devices)

Set HDMI Mode From Configuration Files

Ok, if you are here you are (quite) sure that hardware is ok.

Before going in linux configuration, please get list of supported resolutions by your HDMI monitor/TV.

In many Linux distributions (like Raspberry PI OS but also Debian, Fedora, Ubuntu, etc) HDMI video options can be set from a file named “config.txt” available in SD card boot partition. Once distribution image is flashed on micro SD Card, you will be able to explore this partition from whatever external PC (Windows, MAC or Linux).

config.txt is a simple plain text file which setup system configuration parameters which traditionally are stored using a BIOS. This is read by the GPU before the CPU and Linux are initialised. In Linux systems, this file must be edited as root.

Any changes will only take effect after you have rebooted your Raspberry Pi.

To set HDMI video resolution options you will add 2 parameters: “hdmi_group” and “hdmi_mode”. These parameters must be appended to the end of config.txt.

For example, setting resolution to 1280×720, with frequency at 60Hz and screen ratio to 16:9 (720p) will require following final rows appended to config.txt:

hdmi_group=2
hdmi_mode=85

hdmi_group and hdmi_mode Values

The hdmi_group command defines the HDMI output group to be either CEA (Consumer Electronics Association, the standard typically used by TVs) or DMT (Display Monitor Timings, the standard typically used by monitors). Possible values are:

hdmi_group	result
0	Auto-detect from EDID
1	CEA
2	DMT

Hdmi_mode, in conjunction with hdmi_group, defines video output settings. Hdmi_mode reults depend on hdmi_group value. Possible values for hdmi_mode are:

When hdmi_group=1:

hdmi_mode	Resolution	Frequency	Screen Aspect	Notes
1	VGA (640×480)	60Hz	4:3
2	480p	60Hz	4:3
3	480p	60Hz	16:9
4	720p	60Hz	16:9
5	1080i	60Hz	16:9
6	480i	60Hz	4:3
7	480i	60Hz	16:9
8	240p	60Hz	4:3
9	240p	60Hz	16:9
10	480i	60Hz	4:3	pixel quadrupling
11	480i	60Hz	16:9	pixel quadrupling
12	240p	60Hz	4:3	pixel quadrupling
13	240p	60Hz	16:9	pixel quadrupling
14	480p	60Hz	4:3	pixel doubling
15	480p	60Hz	16:9	pixel doubling
16	1080p	60Hz	16:9
17	576p	50Hz	4:3
18	576p	50Hz	16:9
19	720p	50Hz	16:9
20	1080i	50Hz	16:9
21	576i	50Hz	4:3
22	576i	50Hz	16:9
23	288p	50Hz	4:3
24	288p	50Hz	16:9
25	576i	50Hz	4:3	pixel quadrupling
26	576i	50Hz	16:9	pixel quadrupling
27	288p	50Hz	4:3	pixel quadrupling
28	288p	50Hz	16:9	pixel quadrupling
29	576p	50Hz	4:3	pixel doubling
30	576p	50Hz	16:9	pixel doubling
31	1080p	50Hz	16:9
32	1080p	24Hz	16:9
33	1080p	25Hz	16:9
34	1080p	30Hz	16:9
35	480p	60Hz	4:3	pixel quadrupling
36	480p	60Hz	16:9	pixel quadrupling
37	576p	50Hz	4:3	pixel quadrupling
38	576p	50Hz	16:9	pixel quadrupling
39	1080i	50Hz	16:9	reduced blanking
40	1080i	100Hz	16:9
41	720p	100Hz	16:9
42	576p	100Hz	4:3
43	576p	100Hz	16:9
44	576i	100Hz	4:3
45	576i	100Hz	16:9
46	1080i	120Hz	16:9
47	720p	120Hz	16:9
48	480p	120Hz	4:3
49	480p	120Hz	16:9
50	480i	120Hz	4:3
51	480i	120Hz	16:9
52	576p	200Hz	4:3
53	576p	200Hz	16:9
54	576i	200Hz	4:3
55	576i	200Hz	16:9
56	480p	240Hz	4:3
57	480p	240Hz	16:9
58	480i	240Hz	4:3
59	480i	240Hz	16:9
60	720p	24Hz	16:9
61	720p	25Hz	16:9
62	720p	30Hz	16:9
63	1080p	120Hz	16:9
64	1080p	100Hz	16:9
65	Custom
66	720p	25Hz	64:27	Pi 4
67	720p	30Hz	64:27	Pi 4
68	720p	50Hz	64:27	Pi 4
69	720p	60Hz	64:27	Pi 4
70	720p	100Hz	64:27	Pi 4
71	720p	120Hz	64:27	Pi 4
72	1080p	24Hz	64:27	Pi 4
73	1080p	25Hz	64:27	Pi 4
74	1080p	30Hz	64:27	Pi 4
75	1080p	50Hz	64:27	Pi 4
76	1080p	60Hz	64:27	Pi 4
77	1080p	100Hz	64:27	Pi 4
78	1080p	120Hz	64:27	Pi 4
79	1680×720	24Hz	64:27	Pi 4
80	1680×720	25z	64:27	Pi 4
81	1680×720	30Hz	64:27	Pi 4
82	1680×720	50Hz	64:27	Pi 4
83	1680×720	60Hz	64:27	Pi 4
84	1680×720	100Hz	64:27	Pi 4
85	1680×720	120Hz	64:27	Pi 4
86	2560×720	24Hz	64:27	Pi 4
87	2560×720	25Hz	64:27	Pi 4
88	2560×720	30Hz	64:27	Pi 4
89	2560×720	50Hz	64:27	Pi 4
90	2560×720	60Hz	64:27	Pi 4
91	2560×720	100Hz	64:27	Pi 4
92	2560×720	120Hz	64:27	Pi 4
93	2160p	24Hz	16:9	Pi 4
94	2160p	25Hz	16:9	Pi 4
95	2160p	30Hz	16:9	Pi 4
96	2160p	50Hz	16:9	Pi 4
97	2160p	60Hz	16:9	Pi 4
98	4096×2160	24Hz	256:135	Pi 4
99	4096×2160	25Hz	256:135	Pi 4
100	4096×2160	30Hz	256:135	Pi 4
101	4096×2160	50Hz	256:135	Pi 4
102	4096×2160	60Hz	256:135	Pi 4
103	2160p	24Hz	64:27	Pi 4
104	2160p	25Hz	64:27	Pi 4
105	2160p	30Hz	64:27	Pi 4
106	2160p	50Hz	64:27	Pi 4
107	2160p	60Hz	64:27	Pi 4

When hdmi_group=2:

hdmi_mode	Resolution	Frequency	Screen Aspect	Notes
1	640×350	85Hz
2	640×400	85Hz	16:10
3	720×400	85Hz
4	640×480	60Hz	4:3
5	640×480	72Hz	4:3
6	640×480	75Hz	4:3
7	640×480	85Hz	4:3
8	800×600	56Hz	4:3
9	800×600	60Hz	4:3
10	800×600	72Hz	4:3
11	800×600	75Hz	4:3
12	800×600	85Hz	4:3
13	800×600	120Hz	4:3
14	848×480	60Hz	16:9
15	1024×768	43Hz	4:3	incompatible with the Raspberry Pi
16	1024×768	60Hz	4:3
17	1024×768	70Hz	4:3
18	1024×768	75Hz	4:3
19	1024×768	85Hz	4:3
20	1024×768	120Hz	4:3
21	1152×864	75Hz	4:3
22	1280×768	60Hz	15:9	reduced blanking
23	1280×768	60Hz	15:9
24	1280×768	75Hz	15:9
25	1280×768	85Hz	15:9
26	1280×768	120Hz	15:9	reduced blanking
27	1280×800	60	16:10	reduced blanking
28	1280×800	60Hz	16:10
29	1280×800	75Hz	16:10
30	1280×800	85Hz	16:10
31	1280×800	120Hz	16:10	reduced blanking
32	1280×960	60Hz	4:3
33	1280×960	85Hz	4:3
34	1280×960	120Hz	4:3	reduced blanking
35	1280×1024	60Hz	5:4
36	1280×1024	75Hz	5:4
37	1280×1024	85Hz	5:4
38	1280×1024	120Hz	5:4	reduced blanking
39	1360×768	60Hz	16:9
40	1360×768	120Hz	16:9	reduced blanking
41	1400×1050	60Hz	4:3	reduced blanking
42	1400×1050	60Hz	4:3
43	1400×1050	75Hz	4:3
44	1400×1050	85Hz	4:3
45	1400×1050	120Hz	4:3	reduced blanking
46	1440×900	60Hz	16:10	reduced blanking
47	1440×900	60Hz	16:10
48	1440×900	75Hz	16:10
49	1440×900	85Hz	16:10
50	1440×900	120Hz	16:10	reduced blanking
51	1600×1200	60Hz	4:3
52	1600×1200	65Hz	4:3
53	1600×1200	70Hz	4:3
54	1600×1200	75Hz	4:3
55	1600×1200	85Hz	4:3
56	1600×1200	120Hz	4:3	reduced blanking
57	1680×1050	60Hz	16:10	reduced blanking
58	1680×1050	60Hz	16:10
59	1680×1050	75Hz	16:10
60	1680×1050	85Hz	16:10
61	1680×1050	120Hz	16:10	reduced blanking
62	1792×1344	60Hz	4:3
63	1792×1344	75Hz	4:3
64	1792×1344	120Hz	4:3	reduced blanking
65	1856×1392	60Hz	4:3
66	1856×1392	75Hz	4:3
67	1856×1392	120Hz	4:3	reduced blanking
68	1920×1200	60Hz	16:10	reduced blanking
69	1920×1200	60Hz	16:10
70	1920×1200	75Hz	16:10
71	1920×1200	85Hz	16:10
72	1920×1200	120Hz	16:10	reduced blanking
73	1920×1440	60Hz	4:3
74	1920×1440	75Hz	4:3
75	1920×1440	120Hz	4:3	reduced blanking
76	2560×1600	60Hz	16:10	reduced blanking
77	2560×1600	60Hz	16:10
78	2560×1600	75Hz	16:10
79	2560×1600	85Hz	16:10
80	2560×1600	120Hz	16:10	reduced blanking
81	1366×768	60Hz	16:9	NOT on Pi4
82	1920×1080	60Hz	16:9	1080p
83	1600×900	60Hz	16:9	reduced blanking
84	2048×1152	60Hz	16:9	reduced blanking
85	1280×720	60Hz	16:9	720p
86	1366×768	60Hz	16:9	reduced blanking

For more detailed info, please refer to Raspberry PI config.txt video documentation.

Enjoy!