How to detect progressive vs. interlaced format on HDMI and/or DVI interf?

[tl_rtclancy]

Is there a standard way to detect whether an HDMI/DVI video signal is progressive or interlaced?

Thanks in advance.

[johnmeyer]

Is there a standard way to detect whether an HDMI/DVI video signal is progressive or interlaced?

I'm pretty sure there is, because my TV set will display "1080i" or "720p" when fed video from my U-Verse box.

However, I suspect this is done via HDMI handshake signals. What this means is that unless you are building hardware that you won't be able to get this information. Put another way, the only way the video from that HDMI source can get on your computer or phone is if it is captured. That capture process may, or may not, include all the information that is in the original signal. This is nothing new because, of course, analog NTSC video had all sorts of information embedded in line 21 and elsewhere and almost all of this was routinely stripped by the capture software.

Someone with more insight into HDMI will probably have a better answer.

[pandy]

Is there a standard way to detect whether an HDMI/DVI video signal is progressive or interlaced?

Thanks in advance.

You need to detect is there any temporal difference between fields... so there is no easy way to detect interlace/progressive (you can't prevent situation where progressive content is sent in interlaced video mode over HDMI/DVI).

[johnmeyer]

You need to detect is there any temporal difference between fields... so there is no easy way to detect interlace/progressive (you can't prevent situation where progressive content is sent in interlaced video mode over HDMI/DVI).

Yes, if you try to detect interlaced/progressive by actually looking at the video frames/fields, that is what you have to do. However, since he had the word "HDMI" in there, I assumed he was talking about some of the handshake data that is part of the spec. I am 100% certain that this is how my set knows to display 1080i or 720p.

As for detecting it just by analyzing the video itself, I know this was often discussed a decade ago in the doom9.org forum. What you need is a function that can detect the "teeth" that are visually so obvious when you freeze-frame an interlaced video that has lots of horizontal motion. I can't remember if anyone came up with a good function, but my instinct tells me that this should be possible, especially if you write the function to look at a large number of frames, in order to find frames with lots of movement.

[pandy]

Yes, if you try to detect interlaced/progressive by actually looking at the video frames/fields, that is what you have to do. However, since he had the word "HDMI" in there, I assumed he was talking about some of the handshake data that is part of the spec. I am 100% certain that this is how my set knows to display 1080i or 720p.

Yes, i know, you can observe DDC communication - easy to do by one of those cheap logic analysers like https://www.saleae.com/ or cheaper clone https://hallard.me/cheap-and-usefull-logic-analyzer/ , necessary HDMI DDC (EDID) decoding is already done but at best only selected video mode can be determined not the content...

[tl_rtclancy]

Found my own answer here:

Video Demystified: A Handbook for the Digital Engineer

on page 151 it indicates
1) an odd field (field1) is indicated by coincident hsync/vsync leading edges
2) an even field (field2) is indicated by a vsync leading edge half way through the video line

here is a link to it:
https://books.google.com/books?id=6dgWB3-rChYC&pg=PA151&lpg=PA151&dq=vsync+hsync+in+in...0video&f=false

[johnmeyer]

Found my own answer here:

Video Demystified: A Handbook for the Digital Engineer

on page 151 it indicates
1) an odd field (field1) is indicated by coincident hsync/vsync leading edges
2) an even field (field2) is indicated by a vsync leading edge half way through the video line

here is a link to it:
https://books.google.com/books?id=6dgWB3-rChYC&pg=PA151&lpg=PA151&dq=vsync+hsync+in+in...0video&f=false

Interesting stuff, but what product gives you access to that information? I don't think most capture cards provide a way to query any of the analog signal relationships.

[jagabo]

Found my own answer here:

Video Demystified: A Handbook for the Digital Engineer

on page 151 it indicates
1) an odd field (field1) is indicated by coincident hsync/vsync leading edges
2) an even field (field2) is indicated by a vsync leading edge half way through the video line

here is a link to it:
https://books.google.com/books?id=6dgWB3-rChYC&pg=PA151&lpg=PA151&dq=vsync+hsync+in+in...0video&f=false

That is not the HDMI section of the book.

[manono]

I know that Oppo and some other high-end DVD players (Denon) can do it, in order to prevent such things as interlaced content that was encoded as progressive (it happens) from being passed through unchanged, They can also perform on-the-fly IVTCs, where almost all other DVD players (the flag-reading ones) will simply deinterlace that material.

I know nothing about Blu-Ray players but assume some can prevent mis-encoded material from being passed through incorrectly.

Also, AutoGK pioneered in detecting if DVD material needed to be deinterlaced or IVTC'd or neither. It then went ahead and did what had to be done without user intervention.

[pandy]

Found my own answer here:

Video Demystified: A Handbook for the Digital Engineer

on page 151 it indicates
1) an odd field (field1) is indicated by coincident hsync/vsync leading edges
2) an even field (field2) is indicated by a vsync leading edge half way through the video line

here is a link to it:
https://books.google.com/books?id=6dgWB3-rChYC&pg=PA151&lpg=PA151&dq=vsync+hsync+in+in...0video&f=false

First this book has some errors secondly in HDMI there is no sync information at all (DVI carry such info) besides this gives you nothing except video mode information however you can sent interlace video signal over progressive video mode and opposite).