Is it possible to do appsrc--ximagesink setup in Gstreamer

问题

I want to stream some random bytes to Gstreamer and display it as follows:

[Rand Bytes]--[Video source=appsrc]--[Video sink=ximagesink]

The following Python code I found in this SO post works

source = gst.element_factory_make("appsrc", "source")
caps = gst.Caps("video/x-raw-gray,bpp=16,endianness=1234,width=320,height=240,framerate=(fraction)10/1")
source.set_property('caps',caps)
source.set_property('blocksize',320*240*2)
source.connect('need-data', self.genRandBytes)

colorspace = gst.element_factory_make('ffmpegcolorspace') #To remove

videosink = gst.element_factory_make('ximagesink')
caps = gst.Caps("video/x-raw-yuv,width=320,height=240,framerate=(fraction)10/1,format=(fourcc)I420")
videosink.caps = caps

gst.element_link_many(source, colorspace, videosink)

However if I remove the colorspace part and set videosink.caps as the same as source's, it stops working(nothing happens after clicking start).

My question is why is colorspace needed here? Is it possible to do just appsrc--ximagesink setup?

回答1:

ximagesink doesn't support x-raw-gray, hence the need for colorspace conversion.

Having said that, the documentation says that ximagesink only supports video/x-raw-rgb, so I'm thinking that setting that caps property on the sink isn't doing much. In fact, looking at the output of the sink pad on ximagesource's get_caps() method, it's still video/x-raw-rgb even after that caps property is set and playback has started. Taking out the line setting the caps property has no effect on the output.

http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-base-plugins/html/gst-plugins-base-plugins-ximagesink.html

来源：https://stackoverflow.com/questions/8174898/is-it-possible-to-do-appsrc-ximagesink-setup-in-gstreamer