Re: [Libvisual-devel] Re: Libvisual-devel digest, Vol 1 #193 - 1 msg

[Dennis S. <sy...@yo...>]

On Sun, 2005-02-27 at 02:46 +0100, Jon =C3=98yvind Kjellman wrote:
> Thanks for the advice, I created a small test program that runs, though=
 I =20
> have some issues:
>=20
> 1. The program displays, but doesn't react to the music using alsa inpu=
t. =20
> mplayer plug-in fails with:
> > libvisual ERROR: ./example: inp_mplayer_init(): \
> > Could not open file '/home/jon/.mplayer/mplayer-af_export': No such f=
ile =20
> > or directory

You have to open the alsa capture gain, using alsamixer (this is=20
incredibly lame, I agree). (it works perfectly with alsa here) (your=20
example that is)

> I'm unable to test with others. The examples from CVS failed similarly
> 1. When a plug-in is 8-bit, is it always palette based or can it be gra=
y =20
> scale. How do I determine?

It's palette based, period :) You retrieve the palette from a VisActor=20
using VisPalette *visual_actor_get_palette (VisActor *actor).

> 2. Take a look at display(), are my assumptions about color representat=
ion =20
> good? Does plug-in's use alpha channel?

The framework uses alpha channels for overlaying and such, but plugins=20
themself (are right now) not actively using alpha channels.

I think the color ordering seems right, tho I am not sure how it would=20
hold on other endianess systems. Tho you draw the frame upside down :)
(Just pointing out)

> 3. Why doesn't visual_actor_new("foobar") return NULL if "foobar" doesn=
't =20
> exist?

It's returns a plugin less VisActor. VisActor is just a facade for the
underlaying VisActorPlugin stuff, and it helps you with video=20
negotiation. You can check for a plugin it's existance by doing:
int visual_actor_valid_by_name (const char *name)


> 4. Looking at the source. Why does the for-loop printing input names wo=
rk =20
> (commented out), but the one printing actor names SIGSEGV?

for(i =3D visual_actor_get_list()->head; i; i =3D i->next)
           printf("%s\n", ((VisPluginRef*)i->data)->info->plugname);

Use that, just like with the input_get_list, it's a filtered
list from the global plugin registry (VisPluginRefs) list.

> A last observation. There exists a function visual_video_new_with_buffe=
r() =20
> which will create a VisVideo object and allocate a buffer. However I ha=
ve =20
> found no way to re-size the VisVideo object which will also re-size the=
 =20
> buffer. I have to do this with visual_video_allocate_buffer() (btw. the=
 =20
> docs doesn't mention that this _reallocates_ under certain circumstance=
s.) =20
> Personally, IMHO, I find it a bit inconsistent, the object does keep tr=
ack =20
> of whether or not it's in charge of buffer resizing and could very well=
 =20
> perform the re-size within visual_video_set_dimension().

After a resize, you can safely to visual_video_allocate_buffer, this=20
will free, the old one if it was allocated internally, by
new_with_buffer for example, and after that reallocate a new buffer.

If you manage your own allocated buffer, don't use this function but=20
manage your allocating yourself.

> If you're interested, when I get it to work properly I could create a =20
> short tutorial. However it would need to be reviewed as there probably =
=20
> would be some mistakes.

I am very interested in this, I want to work up our state of docs, I=20
also want to startup a wiki as a source of information and the such.

I understand that you're working on some car multimedia project ? do=20
you have urls regarding this, I am very interested about all this! :)

> Best,
> Jon =C3=98yvind Kjellman

Cheers,
Dennis