[Kdenlive-devel] Jog Shuttle

[Dan Dennedy]

2010/11/20 P. Fleury <fleury at users.sourceforge.net>:
> Hi,
>
> I have tried the jog shuttle, and while it does detect the device, it does
> not seem to do much :-) I am playing with that code, but I am no expert in
> MLT and Kdenlive to begin with.
>
> I have already modified it a bit (wrt to the SVN repository) to handle the
> shuttle in such a way that it does more progressive speeds. 0.5x up to 32x.
> So:
> - it does not seem to wrt well with factors < 1.0x.

It depends on how well FFmpeg (and a little bit MLT based on how it
uses FFmpeg) supports seeking on the format and file you are using.
For example, it works great on DV and other formats without temporal
compression. With formats that take much longer, then it may interact
badly with the frame-dropping algorithm, which you can disable in the
Kdenlive monitor.

> 0.25x and 0.5x do not seem to move the video at all. Is that a known limitation ?

Yes

> - calling the stop() slot on the monitor seems to work only if it is playing
> forward. When it's in rewind mode, that signal does not do anything. A
> wanted feature ?
> - Is there a maximum forward() / rewind() speed ? If not, I think it should
> be a configuration parameter for the jog shuttle.

No explicit maximums. Maybe it need not be configurable but simply
given a good value that seems to work for most.

> - a minor niggle, but why does rewind() take a negative value ? It seems to
> me this is a double negation to say "rewind(-0.5)" if next to it we have
> "forward(0.5)".

I do not know about the Kdenlive methods, but MLT just takes a speed
where negative is reverse, so it must be an artifact of that.

> Once I have these answers, I will be able to produce a patch for this
> change. I own a ShuttlePRO v2, does anyone own another model so we can
> verify that the behaviors are the same ?

I have a first generation ShuttlePro.

> I also plan to work a bit on the buttons, with a better setup and handling
> both more buttons (the SPv2 has 15...) and a few more actions that the ones
> that are currently available. Also, kdenlive cannot detect the jog shuttle
> if it is plugged once it's running, even if the user had configured it
> previously. This change will be a bit more involved, I'll keep it for later
> :-)

In Kino, we made udev rules that send a USR2 signal to kino processes
using killall and then handle that signal in Kino.

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+-DRD-+