dv standart infos

[mont29]

Hi,
I'm coding a dv capture tool, for recording video from a camera, 'in the fields'.
The first releases are available at http://dvgrabgui.sourceforge.net or (for download) http://sf.net/project/dvgrabgui.
Now, I'd like to be able to start/stop the capture just using the REC button of my camera. I think this is possible (the video capture hard drives seem to use this feature), but I hardly can't find any info about it (the IEC standard are'nt donwloadable for free ).
So, if anyone has an idea ...

Thanks by advance,

[JohnnyMalaria]

The DV specification has nothing to do with device control.

Device control is specified by the AV/C Sub-unit protocols.

On Windows, you have to use the avc.sys or avcstream.sys device drivers to communicate with the device via Firewire.

Microsoft exposes user-mode interfaces to these device drivers in DirectShow.

Typically, you use the IAMExtTransport interface.

You have to continually poll the device for its transport state and, when you see that the record button has been pressed, start your capture. Some DV devices are supposed to be able to signal when a change occurs but I have yet to find one. All the devices I have tested have to be polled.

Also, without a recordable tape in the device, the device may not even indicate that the record button has been pressed.

[mont29]

Thanks for the reply, Jhon.
Though I'm coding under linux (sorry, I forgot to say it ), this informations should help me!

[nlec]

I see this is almost 2 weeks old. Nevertheless...

When the playback is stopped the data stream coming in will stop soon after. Would it be possible to set some sort of watchdog timer and detect that the capture buffers are empty and not moving any data?