Viewing a video file's unseen border area footage

[Richard Carter]

Hello,

I might not be explaining this correctly but hopefully someone will understand what I am attempting to do.

A while back I had a Video file (avi) of a CCTV feed which was in the resolution 704 x 288.

I sent it off to an expert forensic company who managed to recover additional video from the borders of the footage, as in the file probably ended up 710 x 234 or something. This extra border footage was previously not shown in the avi.

Basically it seemed that the avi file only played in the specfic 704 x 288 but it had recorded outside of that format and the additional information (surrounding border) was still present in the video file. It was retrieveable using whatever technique they had.

I'm trying to get the background of how this done, what applications are used etc so that I can give it a go on some other feeds.

any ideas?

thanks

[intracube]

How were/are you watching the original .AVI file?

Straight from your CCTV system onto a TV or dedicated video monitor, or on your computer screen?

If you didn't/don't watch on a computer, it's likely that a regular TV or CCTV video monitor would crop the edges of the image due to overscan. This forensic company might have artificially reduced the video (padded the edges with black) to inset the edges and make sure they don't get cropped.

[budwzr]

Certain codecs, like Xvid, have to be cropped by a multiple, like 9 or 6, and cannot be cropped by single pixels.

[Richard Carter]

Hi, thanks for the replies.

The CCTV system has its own application which we used to export to avi format.

The video stream showed the following information:

98.4 kbps 704*288 at 2 fps MPEG-4 Visual (Divx 4) (Simple@L1)

Terrible quality I know but its all we have to work with.

The incident we have occurs on the outer edge of the footage and even a few more pixels outside would assist...

[Nelson37]

With what equipment and/or with what software did you watch the original video? When this was done, was this the converted AVI file or the original CCTV file? Which of these TWO files was sent to the company?

There is no extra data available in a video file. Watched on a PC, with software showing the entire video frame, there is nothing else to be had. There MIGHT be more frame area available in the original file prior to conversion.

If you are watching this on a TV, there is very likely hidden info which can be very, very easily displayed with an extremely minor conversion, as described.