[Kdenlive-devel] capturing

[Jason Wood]

On Monday 22 March 2004 03:12, Rolf Dubitzky wrote:
> 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>

Hi Edwin,

A quick note about the communication between Kdenlive and Piave from a 
programming perspective - in Kdenlive, all of this communication happens in 
the KRender class, and this should remain the case - if you need to send a 
command to piave, you add a new method to KRender that sends the command. To 
recieve messages from piave, you process the command in KRender and emit a 
signal to say the command has been recieved.

All communication is asynchronous, so you need to take this into accout, 
however that does not normally make coding more complicated, it just requires 
a different mindset.

>
> 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">

This interface looks fine to me.

The only difference I would suggest is to remove the <captureGetDevices> 
command and add the information of the return message to the 
<getCapabilities> reply that already get's sent. (you can add this now; it 
will not affect kdenlive).

If you add the capture commands, you might be able to test them out using the 
new "send veml command" box in the debug dialog before the ui is complete.

Cheers,
Jason

-- 
Jason Wood
Homepage : www.uchian.pwp.blueyonder.co.uk