[Kdenlive-devel] capturing

[Rolf Dubitzky]

On Sunday 21 March 2004 22:05, Edwin Schepers wrote:
> I have a digital camera. I'll have a look at pgrab. I don't have any
> knowledge (outside some kde programming), but that will only take time
> (well, only... :-)
> I never grabbed with Linux, but I'll get it working.
> Then I could start making a gui in kdenlive.

That sound very good. I don't know how much you know about kdenlive/piave, but 
you probably have already understood, that kdenlive is the GUI part which 
depends _only_ on KDE/Qt and piave is the render engine which has all kinds 
of nasty dependencies on the file, audio, and video formats, audio systems, 
video systems and ieee1394 interface. The two components comunicate via a 
pretty simple protocol over sockets. This protocol needs to be extended to 
handle all that is necessary for capturing (which is trivial). I am _very_ 
interested in cpturing capabilties, so if you are really interested, I can 
implement all the necessary changes in piave and code all the communication 
to the actual hardware (most of this is already done anyway). 
So if you start creating a GUI component in kdenlive, all you need to do is 
send commands via the (existing) communication channel to piave. You don't 
need to bother with the underlying hardware. (In fact, you must not, since 
kdenlive should be independent of hardware dependencies)

So the first command to send would probably be something like

<captureGetDevices>

to see what is actually attched to the PC. piave would answer something like 
the following (run "pgrab -v 2" to see if/how your cam is reported)

<captureDevices>
    <ohci1394>
        <device devid="0" name="Sony DCR-TRV30E" type="AVC (subtype=VCR)" />
    </ohci1394>
</captureDevices>

 The device id is an integer for further reference of the device. The name is 
actually read from the device itself and can be displayed to the user. In 
case more than one device is attached, you can offer a selection box or 
whatever. 
 Then kdenlive could then send commands like

<capturePlay devid="0">

and

<captureRecord devid="0">
<captureStop devid="0">
.
.
.


I havn't really thought it through, that's just what comes from thetop of my 
head. Shouldn't be too dificult to come up with a reasonable syntax and set 
of commands. 

Cheers, Rolf

-- 
contacts: http://www.physi.uni-heidelberg.de/~dubitzky