Basics of gstreamer pipeline

Tim-Philipp Müller t.i.m at
Wed Oct 31 03:27:49 PDT 2012

On Wed, 2012-10-31 at 18:17 +0900, Praveen Adi wrote:


> Can some please explain me the following:
> In the pipeline,
> gst-launch videotestsrc ! ffmpegcolorspace ! ximagesink
> What cololorspace does videotestsrc  produce here?

It will query ffmpegcolorspace for what it supports, which in turn will
query ximagesink for what it supports (so that what ximagesink supports
can be prefered).

It will likely produce whatever colorspace/pixel layout ximagesink
returns first in the caps it returns from its get_caps() function.

> What colorspace conversion is ffmpegcolorspace doing?

If videotestsrc can produce every format ximagesink could possibly
support, then no conversion will be done. ffmpegcolorspace will operate
in passthrough mode.

> What colorspace is ximagesink accepting and where is it presenting,
> Framebuffer??

It depends on the driver/card. It will be determined at runtime what
formats are supported. It's likely going to be some RGB format.

You can see the caps negotiated if you pass -v to gst-launch.

> Here we don't mention any properties for the plugin, but still how do
> they co-work?

Not sure I understand the question, could you rephrase it?


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