Output PAL 576i over HDMI from PC then Input to BMD Decklink?

[213]

Hi, new to the forum and not sure which section this would most be appropriate for as could come under a few so posted in general.

Situation:

I am trying to output a PAL standard 576i video signal from my PC over HDMI, but I am unsure on the timings and advanced settings required to do so.

I am hoping to take this PAL over HDMI into my blackmagic decklink to then output as PAL over S-Video, to connect to a PAL CRT monitor.

The source material I am looking to play on the monitor is in 576i, hence why I am trying to keep the resolution as this throughout the conversion, as opposed to doing a 1080p HDMI down conversion to S-Video for example, via the decklink settings.


My graphics card (AMD) allows for custom resolutions, but when I input 720 x 576 50hz nothing is detected on the decklink (presumably as the signal standard is not correct). There are advanced settings and timings but I have no idea what these would need to be to be compatible:

[Attachment 62964 - Click to enlarge]

Am I over thinking this or is it just the case of inputting the correct timings and settings which would then allow the decklink to recognise the PAL signal via the HDMI input?

Many thanks in advance for any help that can be given!

[usually_quiet]

Which BMD Decklink model do you have?

[pandy]

Isn't Declink shall provide over HDMI supported video mode and such video mode should be available on your graphic card. if i recall correctly all HDMI graphics card follows such path - set Declink to desired mode and i should be available on your PC.

Proper timings (i.e. values for creating arbitrary mode) for HDMI predefined modes a.k.a. "Short Video Descriptor" (predefined as HDMI support also user modes a.k.a. "Detailed Timing Descriptor" but issue may be on Decklink side and such modes may be not supported) are provided in CEA-861-xx (where xx means capital letter and it should be equal or higher than D).

Video ID Code:
21 720(1440)x576i 50Hz 4:3 16:15
22 720(1440)x576i 50Hz 16:9 64:45

Timing values are provided also on https://en.wikipedia.org/wiki/Extended_Display_Identification_Data#CEA_EDID_Timing_Ext...at_-_Version_3

Table "EIA/CEA-861 standard resolutions and timings "

[213]

Which BMD Decklink model do you have?

Its a Decklink 4k Extreme 6G


[Attachment 62972 - Click to enlarge]

[213]

Isn't Declink shall provide over HDMI supported video mode and such video mode should be available on your graphic card. if i recall correctly all HDMI graphics card follows such path - set Declink to desired mode and i should be available on your PC.

Proper timings (i.e. values for creating arbitrary mode) for HDMI predefined modes a.k.a. "Short Video Descriptor" (predefined as HDMI support also user modes a.k.a. "Detailed Timing Descriptor" but issue may be on Decklink side and such modes may be not supported) are provided in CEA-861-xx (where xx means capital letter and it should be equal or higher than D).

Video ID Code:
21 720(1440)x576i 50Hz 4:3 16:15
22 720(1440)x576i 50Hz 16:9 64:45

Timing values are provided also on https://en.wikipedia.org/wiki/Extended_Display_Identification_Data#CEA_EDID_Timing_Ext...at_-_Version_3

Table "EIA/CEA-861 standard resolutions and timings "

Thanks for the info, however still struggling to make sense of it unfortunately.
The default resolutions on windows are:

[Attachment 62973 - Click to enlarge]

I have added the timings you provide on the wiki page for #21 / #22 but it won't let me save as it is incompatible:

[Attachment 62974 - Click to enlarge]

Not sure if this is due to the fact the 'Front Porch', 'Sync Width' and polarity options were not inputted as I could not see reference to them on the Wiki?

Let me know if I am missing something, and thanks for your advice so far!

[Skiller]

Try these:


[Attachment 62993 - Click to enlarge]

You may also need CRU (Custom Resolution Utility) to override what the driver thinks your "display" is capable of.

[213]

Try these:


[Attachment 62993 - Click to enlarge]

You may also need CRU (Custom Resolution Utility) to override what the driver thinks your "display" is capable of.

Hi, many thanks for this - I tried the settings first in AMD control panel but it said they were incompatible as expected.
I then put them in CRU but I can't get it to actually display at the inputted resolution 576i. It doesn't show in the windows display settings or advanced settings.

[Attachment 62994 - Click to enlarge]

I deselected all the other resolutions to avoid any conflict but the only res that shows now is 640 x 480:

[Attachment 62995 - Click to enlarge]

Although now in NTSC, it is a little closer to what I am aiming for as the BMD Decklink now shows NTSC input via HDMI:

[Attachment 62996 - Click to enlarge]

However it is a scrambled mess on the CRT:
https://imgur.com/fZKkrDm

The CRT is NTSC compatible so its not the cause if the scrambled picture, it must be again due to some irregularity in the signal that the GPU is outputting?


Any ideas why the 576i res specified in CRU is not showing up?

Thanks again for everyone's help on this!

[Skiller]

What does it say if you click on "Edit..." here?


[Attachment 62997 - Click to enlarge]

Any ideas why the 576i res specified in CRU is not showing up?

Windows likes to hide low resolutions (I think anything below 800x600), and there should be a way to stop this but did you try setting the resolution in the GPU driver instead of Windows?

[pandy]

IMHO issue is on Declink side - HDMI works in such that display (Sink) tells to HDMI Source (your graphics card) what video modes can display and in theory only those modes can be set on you source. I would check Decklink also for this - how to force particular video mode especially that EDID is on Decklink dynamic (so you need to set manually capture resolution) - you can do quick test - use some TV as display - connect to your graphics card - new video modes should be available in video modes list - IIRC AMD need to have active checkmark for TV video modes (rely on memory for my Radeon 7850 - perhaps newer AMD drivers behave differently)

Forgot to add - HDMI can't have such low pixelclock (13.5MHz) - for 720x576i video mode so called pixel repetition mode is used (so your 720x576i is in fact 1440x576i) so pixelclock is twice faster i.e.27MHz (this is ancient VGA limitation - no clock bellow 25MHz is allowed by HDMI)

Bellow timings for 720x576i from CEA-861-E.


[Attachment 62998 - Click to enlarge]

[Attachment 62999 - Click to enlarge]

[213]

IMHO issue is on Declink side - HDMI works in such that display (Sink) tells to HDMI Source (your graphics card) what video modes can display and in theory only those modes can be set on you source. I would check Decklink also for this - how to force particular video mode especially that EDID is on Decklink dynamic (so you need to set manually capture resolution) - you can do quick test - use some TV as display - connect to your graphics card - new video modes should be available in video modes list - IIRC AMD need to have active checkmark for TV video modes (rely on memory for my Radeon 7850 - perhaps newer AMD drivers behave differently)

Forgot to add - HDMI can't have such low pixelclock (13.5MHz) - for 720x576i video mode so called pixel repetition mode is used (so your 720x576i is in fact 1440x576i) so pixelclock is twice faster i.e.27MHz (this is ancient VGA limitation - no clock bellow 25MHz is allowed by HDMI)

Bellow timings for 720x576i from CEA-861-E.


[Attachment 62998 - Click to enlarge]

[Attachment 62999 - Click to enlarge]

You're right, it worked!

[Attachment 63078 - Click to enlarge]

[Attachment 63079 - Click to enlarge]

It is quite stretched given its probably displaying at square pixel ratio, but not really an issue as I can stretch the playback media horizontally to fill screen and then it looks normal on the CRT.

[Attachment 63080 - Click to enlarge]

Many thanks for everyone's help!

[pandy]

You're right, it worked!

[Attachment 63078 - Click to enlarge]

[Attachment 63079 - Click to enlarge]

It is quite stretched given its probably displaying at square pixel ratio, but not really an issue as I can stretch the playback media horizontally to fill screen and then it looks normal on the CRT.

[Attachment 63080 - Click to enlarge]

Many thanks for everyone's help!

It may work but it is not entirely correct - you should have 720x576 as special mode called pixel repetition is used - so source and destination will be 720 pixels in line but transparently HDMI will use double number of pixels to increase clock above 25MHz to satisfy DVI (CEA861) limitations.
Not sure how to force pixel repetition on AMD driver - perhaps you should contact with AMD on this...

https://ez.analog.com/video/f/q-a/105329/adv748x-relationship-between-pixel-repetition...cy-calculation

=============================================================================
5.3.6 Pixel Repetition
hdmi_pixel_repetition[3:0], HDMI RX Map, Address 0x05[3:0] (Read Only)
This signal is a readback to provide the current HDMI/MHL pixel repetition value decoded from the AVI Infoframe received.
The HDMI/MHL receiver automatically discards repeated pixel data and divides the pixel clock frequency appropriately as per the pixel repetition value.
=============================================================================

https://en.wikipedia.org/wiki/HDMI#Specifications

Video formats with rates below 25 MHz (e.g., 13.5 MHz for 480i/NTSC) are transmitted using a pixel-repetition scheme.