[vlc-devel] Re: input callback

Vaclav Koldus vaclav.koldus at avpark.cz
Thu Jan 19 13:03:25 CET 2006

Sigmund Augdal Helberg napsal(a):

>On Wed, 2006-01-18 at 16:05 +0100, Antoine Cellerier wrote:
>>On Wed, Jan 18, 2006, Vaclav Koldus wrote:
>>>That's why I would rather add a callback to input. Now this would work 
>>>fine, but
>>>in future I want to use VLM. Is there any possibility??
>>The issue is that you can't really add a callback to input since it is
>>killed and respawned when a new one is needed. (Someone correct me if
>>i'm wrong)
>>And i don't know about any similar callback variable that the vlm
>>media element might update when changing the input it's using. (That
>>wouldn't be too hard to add i guess)
>You could probably grab a hold on the input (using vlc_object_find) and
>then query it's b_die at regular intervals. And then trigger a name
>renewal at this time. make sure you call vlc_object_release once b_die
>is set, otherwise you'll get nasty errors. 
>After the current input has died there could probably be a while when
>there is no input before a new one is spawned, you should handle this
>Btw, what kind of module are you working on? If it is (as you say) a
>child of the input, then the module will very likely be killed as well
>when the input is.
Well, I don't know VLC object strucure well enough to say it is/isn't 
child of the input. I've just tried to find parent and it worked.
In fact I'm writing video filter module. It renders various videotext 
informations on the screen. I wanted it to depend on
the filename (to decide whether show some info.) At this rate I use 
playlist so callback on playlist is OK now.
Anyway video filter isn't killed with input as I've found out.

In future I want to use VLM to achieve better timing of played files and 
use the mosaic principle to show multiple videos
in one output (PIP etc.) Because there are special requirements on this 
filter I decided not to use VLC built in
features and write my own. I've got my own YUV rendering library using 
freetype to render text and simply
draws images in native YUV. Screen templates are defined in XML files 
and now I'm working on scheduling them
by mysql based queue. I will need to solve another problem here, cause I 
can't simply use the filename for
decisions when there are multiple source files. I haven't thought over 
this yet so there's probably no point in bothering
with VLM sources now.

Only original VLC filter I took advantage of is blending filter. Here 
I've got a question. I don't understand
the blending filter code a bit so I don't know. Is there any chance to 
improve performance of blending
by rewriting it in sse2 or mmx? I already had some performance issues 
with my filter. I optimized
colorspace conversions (in DV decoding/encoding, another part of my 
project) by sse2 which was
enough for now but what when the requirements raises again?
I think blending is a good candidate for optimalization. Or am I wrong?



>Hope this helps (and works).
>>Antoine Cellerier

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