How can I read a video file that is being created?

I have a very old video capture device (Dazzle DVC USB) hooked up to Windows7, and it works with the program that it came with just fine to create a MPEG2 file in a directory.

However, I want to stream what I am recording instead of saving it to a file. The best solution I can think of is playing the video file with VLC or some other program, then capturing the output with Procaster (from Livestream.com). Thus, I want to read a video file as it is being written, and Windows doesn't like that at all. Is there any way to bypass the warnings and read the file anyway? I don't need to do anything fancy like seeking, so is this possible/safe?

Otherwise, other methods that let me stream the feed while it is live that would work with my device, the Dazzle DVC (Digital Video Recorder). I can provide as much information about the device as a person might need.

VolatileRig

Posted 2011-11-01T03:56:31.873

Reputation: 91

1It's not very easy to do this under Windows. If the device's driver uses a standard interface, you should be able to "open" the device directly in VLC. Then you can stream and save it to disk at the same time using VLC. – billc.cn – 2011-11-01T04:06:14.297

Nope, VLC gave me some error that the device didn't accept certain parameters, otherwise I would do that... – VolatileRig – 2011-11-01T04:09:16.227

And you really can not use a different software to record from the DVR? Try http://dl.dropbox.com/u/16862782/AMCAP.EXE for example. Amcap will not allow you to stream, but it usually allows you to at least access the card if it is compatible with directshow. I heard though that the dazzle cards might just not be compatible with it..

– sinni800 – 2011-11-10T17:17:17.523

Answers

There is some software (ManyCam) which "splits" webcam signals. It installs as multiple virtual webcams, so you will be able to save it using one software and previewing using another.

Not sure if your Dazzle DVC works with this software, but it's worth testing it as this is free software.

Possibly you will have to use some other recording software, but I guess finding a free one should not be a problem.-

Jens Erat

Posted 2011-11-01T03:56:31.873

Reputation: 14 141

A workaround could be to use some linux VM for doing this. Mythbuntu is a live CD containing lots of software, the driver for your TV is contained in Linux kernel since end of 2008. As there is no mandatory file locking you will be able to read a file while writing it.

You could also use some linux NAS to write to and read it at the same time. Samba could handle windows locks. Microsoft writes there is no mandatory file locking when using NFS, so you could use a nfs server. Requires a second box or linux vm, too.

Jens Erat

Posted 2011-11-01T03:56:31.873

Reputation: 14 141

The article How to: Start watching video while still downloading describes how to use VLC for watching partial video :

Assuming that the download is called x.avi, or if it is of length zero than probably one needs to locate a file called x.avi.part which is growing up
Start VLC and drag the above file to it
VLC will ask to repair the file : Click "Don't repair"
If the download completes while you are playing and the download software gives an error because it was unable to rename the .part file, you may need to rename the file yourself.

Read also the article 3 Easy Ways To Preview a Partially Downloaded Video Files, which apart from VLC, also describes using :

DivFix++ : capable of fixing broken AVI file, rebuild the index of the video and allows you to playback in a media player.

GOM Player : its patented technology allows playing broken AVI files on the fly.

If your problem is not only that of playing a partial file, but also that this file is locked while downloading from being used by other programs, then the free product Unlocker can be used to unlock such files and make them available for reading.

harrymc

Posted 2011-11-01T03:56:31.873

Reputation: 306 093

Unlocker doesn't help you in here as it removes the locking processe's file handle, so this will recieve an I/O error and stop recording the movie. – Jens Erat – 2011-11-06T10:42:43.500

@JensErat: Wrong - Unlocker has several functions, among them unlock and delete. The unlock function does not delete the file. – harrymc – 2011-11-06T15:16:08.123

Never spoke of deleting the file, it removes the processes handle. You will be able to access the file, but the first process will not be able to write to it any more. Just tested it to be sure. Unlocker cannot help you in here. – Jens Erat – 2011-11-06T16:18:38.527

@JensErat: One cannot "remove" a file handle that is in use by another process, or that process will crash. One can only remove the exclusive lock held on the file by that process, two very different API calls in Windows. This I have done with Unlocker in the past without harming the first process. There may be differences between my experience and yours, if the first process doesn't take kindly to losing its lock on the file. For example, if it tried to renew its lock and found it couldn't because the second process was reading it. So it all depends on the programming of the first process. – harrymc – 2011-11-06T17:49:15.483

I mainly tested it using windows explorer, just copy a big file and use unlocker. Unlocker's internet page also says unlocker would be closing the handle, look at the feature table. What software can continue writing? Really interested in that as this conflicts with either unlockers internet page or my understanding of file access within windows applications...

– Jens Erat – 2011-11-06T18:53:10.427

@JensErat: I really don't remember which was the program that continued for me, but of course unlocking can derange any program. For example, maybe renaming x.avi.part to x.avi and deleting x.avi.part will become impossible because x.avi.part is being played, so the download program will abort with x.avi entirely missing. One has to try and see, admittedly with a rather good chance of lousing things up. Playing like this with a running program is certainly not recommended without a pre-test or if the program is not restartable with resume, because there is no way of reinstating the lock. – harrymc – 2011-11-06T20:35:12.157

I'd suggest to either go with VLC (as mentioned by @harrymc), choosing to not repair the file when asked, or as a second choice try with some video stream editors in the VirtualDub family, like the original one or its modded version. With the last two probably you'll not be able to listen any sound, though.

superjos

Posted 2011-11-01T03:56:31.873

Reputation: 296