Vido capture display and review

[Malcolm S]

I have an application wheter I want to capture and display video in real time on a PC, however while recording continues, I want to be able to rewind the video to any point and then view the video at that time. It would be nice to be able to place automatic 'book marks' at say 20 second intervals, or be able to press a key and record a 'book mark'.

Any suggestions, please.

[Malcolm S]

Sorry, I forgot to say that I am capturing from a Digital video camera via USB.

[poisondeathray]

This won't be possible because you can't access a video file while it's still recording .

It might be possible with some method where you capture fragments or certain time lengths , or if you recording a still image format (like a png or jpg sequence)

[jagabo]

This won't be possible because you can't access a video file while it's still recording .

That isn't quite true. Some applications will write the file in non-exclusive mode. That allows other applications to read the file while it's still being written to. I do this all the time to check on x264 CLI MKV encodings -- I play the file with a media player while x264 is still encoding.

The biggest problem is that most applications only check the file length when the first open the file. So they won't be able to see what was written later. But it should be possible for a program to check the file length periodically and allow access to later parts of the file.

[vhelp]

some years, i used a computer at work, windows 2000 pro, that allowed me to read from it while at the same time writing to it, in all my apps. some of those were video apps/encoders, for instance. i believe that it is possible if you set something up in windows. then the app can create the file while another (external) app can read it in read-only mode. i never did find out how it was possible. that was back in 2005/2006 ish. i don't know about windows xp/vista/7 or 8 though. i think it might be possible for an external app to still open a file for reading while it is being written to. it might have to be read using a special read-only routine. some programming lanuages may provide methods for this though the correct param setup may be undocumented. although i haven't tested it, i think delphi may have such a method like this. but if a developer doesn't know about this, then the app may not allow even read-only mode access.

[jagabo]

Shared access is part of the Windows API for creating or opening a file:

http://msdn.microsoft.com/en-us/library/windows/desktop/aa363858%28v=vs.85%29.aspx

Whether or not other programs can read/write the file depends on whether or not the program that created it (or for an existing file, first re-opened it) allowed shared access.