Compare 2 Video frames 5 seconds apart

[alon24]

Hi all,

Since I am new to the whole video/frame editing I did not know where to ask.

I use SageTV (PVR) and would like to write a plugin, that checks when a code is needed and sends it.

Explanation:
The Sat company uses a parental control (or PPV) system, that when entering the channel, it expects you to put your code in.

I want to record these stations, but have no means of knowing how to figure out if the code is needed (I can handle sending it).

I figured out that the stupidest way would be to take 2 frames, 5 seconds apart and compare them. If they are the same, enter the code.

I need a method to compare 2 frames, and so I ask here.

I have an mpg, or I can get the 2 pics out of the file.
Since this is an analog source, and I have not done a lot of image work, I need a FREE way to do this.

Can any1 help??
Thanks,
alon24

[anosis]

Could you not just define which channels are PPV channels and have the plugin send the additional IR codes then.

I assume you must have some programming background. Your plugin would have to intercept channel changes and compare the channel selected by Sage with a list of channels you know need the code. Then you respectively your plugin would have to send the additional digits for the code.

Your idea is good but I am worried that even though the two snap shots will be almost identical they will be slightly different. They are not digital snap shots of the same picture but rather two analog shots where the capturing card will introduce some artifacts that make them unequal - hence this is where the problem lies to compare them. It could be that you are looking at a logo at the beginning of the show that stays on the screen for more than 5 secongs and that could trigger your plugin as well if you manage a way to accurately compare the two.

Are you using IR blaster or is this via RS232 to change channels?

[alon24]

I do have a strong programing background.
I can listen for when a channel changes.
I can extract any number of pictures I like at any time, I chose 2 frames 5 seconds apart.

The PPV/Parental control is a little bit tricker, for the parental control, if you are on the channel, then enter the code, if you do not change the channel you do not need to enter the code again.

But if you changed the channel, then when coming back, you need to enter the code again.
In short it varies...


I can do all the things from above I just need to comapare a region, I wouldnt even mind counting black pixels or something like that, and if there is a diffrential of a fixed precentage, then I would accept it as the same pic.

I can further choose the channels this will happen on, and a start and end time (23:00-6:00) to minimize the false readings.

I just need to compare the 2 frames...
CAn ayone help with that?