[gst-devel] Text rendering

Gergely Nagy gergely.nagy at gmail.com
Sun Feb 20 08:35:27 CET 2005

On Mon, 21 Feb 2005 01:40:48 +1100, Jan Schmidt <thaytan at noraisin.net> wrote:
> On Sun, 2005-02-20 at 15:09 +0100, Maciej Katafiasz wrote:
> >Is it really going to be expensive if most of that image will be 100%
> >alpha anyway?
> Yes, it's more expensive to write out and then drag in 2 entire frames
> worth of overlay image from main memory and iterate over it ~25 times
> per second if you don't have to.
> There's a need for an imageoverlay to do this, but I think there's also
> a place for a text renderer that draws straight onto the image buffer.

I'd like to believe there is no need to have two elements that do
almost the same thing, but rather have one, that can efficiently do
both tasks.

> A possibly-decent alternative would be to provide the rendered
> text-as-image overlay frames to the imageoverlay in a new frame format
> that isn't just a raw image frame, but has a header describing
> cropping information at the start of each frame.

How about rendering the text only (then, the buffer will be eg,
174x48), setting the caps on the srcpad appropriately (so the mixer
notices the dimension change), and optionally telling the mixer in one
way or the other the new position at which blending should occur? (Eg,
by setting the mixers xpos/ypos properties, or somesuch)

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