[vlc-devel] Re: Snapshot - 3 frames at a time

[Olivier Aubert]

> I would like to take snapshot of video 3 consecutive frames at a time.
> What is the best way to do so?
> P.S.  Actually, is it possible to buffer 3 frame first and then save
> it in one shot.  I would prefer this way if possible.
This is why I developed the snapshot video output module (cf
modules/video_output/snapshot).

* Context: I am working on an video annotation software, so I need to
take into account the reaction time of the user wishing to create new
annotations. 

* Principle: the snapshot video output is a dummy video output that
caches a copy of a configurable number of frames, at a specified
resolution. It is used via the clone video filter :

vlc --video-filter clone --clone-vout-list default,snapshot

* Access to the data: it is for the moment only possible from the
python-vlc module and the vlc-corba module, through the common code
stored in src/control/audio_video.c (mediacontrol_all_snapshots,
mediacontrol_snapshot). It is easy to add a hotkey to call these
functions too.

These are not optimal: the timestamps for pictures is not exact (maybe
the new access architecture would allow more precision, I have not
touched this code for a while), and it could reuse the standard vlc
structures instead of defining its own. But it works for me for the
moment. I welcome any contributions and suggestions on this subject (and
also on the proposed MediaControl API, cf
http://wiki.videolan.org/index.php/MediaControlAPI).

Hope this will help,
Olivier


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